KR102119872B1 - Misfire diagnosis method and system of single cylinder four-stroke engine - Google Patents

Abstract

Disclosed are a method and apparatus for diagnosing misfiring of a single-cylinder four-stroke engine. According to an embodiment of the present invention, the method of the present invention comprises: a data collection step of collecting signal data output by a crankshaft position sensor during two engine cycles; a discrete Fourier transform step of applying a discrete Fourier transform to the signal data during the two engine cycles collected in the data collection step to quantify the same in a frequency form; a PSD calculation step of calculating a power spectrum density (PSD) from frequency data converted in the discrete Fourier transform step; and a misfiring diagnosis step of analyzing a harmonic order value exhibiting a maximum value of the PSD calculated in the PSD calculation step to diagnose whether the misfiring occurs. According to the present invention, the misfiring can be simply and accurately diagnosed and detected.

Description

Misfire diagnosis method and system of single cylinder four-stroke engine}

The present invention relates to a misfire diagnosis method and apparatus for a single-stroke four-stroke engine, by applying a discrete Fourier Transform to the engine speed extracted from the engine cycle subject to misfire analysis, quantitatively grasp the fluctuation of the engine frequency and make a misfire ( Misfire) relates to a method and apparatus for diagnosing misfires in a single-stroke four-stroke engine.

Misfire is a phenomenon in which fuel injected from an engine using fossil fuel does not burn and is discharged to the outside air as it is. When an engine misfire occurs, unburned fuel is discharged as it is, adversely affecting air pollution, or unburned fuel may be burned in the catalyst and damage the catalyst.

Accordingly, in the case of a general vehicle, the misfire detection logic is installed in the ECU to diagnose misfire to prevent air pollution or catalyst damage. An engine roughness method for diagnosing misfires by extracting an engine speed from a tooth time signal measured by a crankshaft position sensor is mainly applied to automobiles.

In addition, a technique for determining misfire by measuring the ionic current of a combustion pressure sensor or an ignition plug is also known.

On the other hand, in the global trend in which exhaust emission regulations are being strengthened day by day, two-wheeled motorcycles, which were not previously included in the regulation, are also not free from exhaust emission regulations. Therefore, two-wheeled motorcycles are also in the market to meet emission regulations. There is a need for technical supplementation to meet the needs.

One of the countermeasures to meet the demands of this market is the attempt to apply the true-fire detection technology that has been applied to general automobiles to motorcycles. However, it is difficult to apply the true fire detection technology applied to a general vehicle to a motorcycle.

In general, misfire detection technology applied to automobiles includes a fairly complicated process due to the characteristics of a multi-cylinder engine, and ECUs generally mounted on two-wheeled motorcycles are inexpensive and have low processing performance compared to automobiles. Therefore, it is difficult to apply the true detection technology of automobiles to ECUs of motorcycles.

Accordingly, in accordance with the market demand according to the exhaust emission regulations that are being strengthened worldwide, there is a need for a true fire detection technology suitable for the characteristics of two-wheeled motorcycles. In other words, a simple and optimized technique for accurately detecting/detecting misfires optimized for two-wheeled motorcycles is needed.

Korea Registered Patent 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 misfires of a single-stroke four-stroke engine that can diagnose/detect misfires simply and accurately compared to misfire detection technologies of automobile multi-cylinder engines.

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

As a method of diagnosing misfires occurring in a single-stroke four-stroke engine using the output signal of a crankshaft position sensor,

a) a data collection step of collecting signal data output by the crankshaft position sensor during two engine cycles;

b) a discrete Fourier transform step of quantifying a frequency form by applying a discrete Fourier transform to signal data for two engine cycles collected in the data collecting step;

c) a PSD calculation step of calculating a power spectrum density (PSD) from the frequency data converted in the discrete Fourier transform step; And

d) a misfire diagnosis step of diagnosing misfire by analyzing a harmonic order value in which the maximum value of the power spectral density calculated in the PSD calculation step appears; includes,

The two consecutive engine cycles constitute one misfire analysis target section, and one misfire analysis target section overlaps the preceding misfire analysis target section and one engine cycle, and the misfire diagnosis method of the short-term four-stroke engine is characterized. Gives

Here, the discrete Fourier transform step, after removing the linear trend from the crankshaft position sensor output signal data during the two engine cycles collected in the data collection step, based on the angular velocity of the crankshaft position sensor output signal data frequency It is characterized by being converted to an ingredient.

In addition, in the misfire diagnosis step, when the maximum value of the power spectrum density appears at a value where the harmonic order value is not 1, it is characterized in that it is diagnosed as normal ignition.

On the other hand, in the misfire diagnosis step, when the maximum value of the power spectral density appears at a harmonic order value of 1, it is characterized by diagnosing that misfire has occurred.

In addition, in the misfire diagnosis step, the maximum value of the power spectrum density at a harmonic order value of 1 appears, and the maximum value of the power spectrum density at a harmonic order value of 1 is the power spectrum of the misinterpretation target section diagnosed as the previous misfire. If it is larger than the maximum value of density, it is characterized by diagnosing that a misfire occurs continuously in two engine cycles.

In the misfire diagnosis step, if the engine speed at the end of the exhaust stroke is smaller than the initial engine speed of the second engine cycle among the two engine cycles included in one misfire analysis target section, the diagnosis is made as continuous misfire. It is characterized by.

In addition, a further down-sampling step of down-sampling the signal data by the crankshaft position sensor during the two engine cycles collected in the data collection step prior to the discrete Fourier transform step (Down sampling); further includes.

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

A system for diagnosing misfires occurring in a single-stroke four-stroke engine using the output signal of a crankshaft position sensor.

A discrete Fourier transform unit converting the signal data output by the crankshaft position sensor during two engine cycles into a discrete Fourier transform;

A PSD calculating unit calculating a power spectral density (PSD) from the discrete Fourier transformed frequency data through the discrete Fourier transform unit;

Includes; a misdiagnosis diagnosis unit for diagnosing a misfire by analyzing a harmonic order value in which the maximum value of the power spectrum density calculated by the PSD calculation unit appears;

The two consecutive engine cycles constitute one misfire analysis target section, and one misfire analysis target section is a misfire diagnosis system for a short-term four-stroke engine, characterized in that the preceding misfire analysis target section and one engine cycle overlap. Gives

Here, the signal processing unit for down-sampling the signal data output from the crankshaft position sensor prior to the discrete Fourier transform through the discrete Fourier transform unit at regular intervals; further includes a.

The discrete Fourier transform unit removes the linear trend from the signal data output by the crankshaft position sensor during the two engine cycles, and then converts the signal data output by the crankshaft position sensor into frequency components based on the angular velocity of the crankshaft. It is characterized by letting.

In addition, the misfire diagnosis unit is characterized in that when the maximum value of the power spectral density appears when the harmonic order value is not 1, it is diagnosed as normal ignition.

In addition, the misfire diagnosis unit is characterized in that when the harmonic order value is 1, the maximum value of the power spectrum density appears, the misfire has occurred.

In addition, the misfire diagnosis unit, the power spectrum of the misinterpretation analysis target section in which the maximum value of the power spectrum density with a harmonic order value of 1 appears and the maximum value of the power spectral density with a harmonic order value of 1 has been diagnosed as the previous misfire. If it is larger than the maximum value of density, it is characterized by diagnosing that a misfire occurs continuously in two engine cycles.

In addition, if the engine speed at the end of the exhaust stroke is smaller than the engine speed at the initial stage of the explosive stroke of the second engine cycle among the two engine cycles included in one misfire analysis target section, the misfire diagnosis unit diagnoses the misfire as continuous misfire. It is characterized by.

According to a misfire diagnosis method of a single-stroke four-stroke engine according to an embodiment of the present invention, a discrete Fourier transform is applied to the engine speed for each stroke of a section to be analyzed to quantify it in the form of an engine frequency, and the section to be analyzed by the discrete Fourier transform It is configured to diagnose whether the normal ignition or misfire (Misfire) by analyzing the engine frequency of the.

In other words, it is a method to diagnose/detect a true story with only the minimum key information that can clearly determine whether it is true. It is possible to provide an optimized misfire detection function suitable for the situation of a two-wheeled motorcycle using a low-cost ECU compared to an expensive ECU.

As a result, in the global trend of exhaust emission regulations being strengthened day by day, it is possible to meet the market demand to meet the emission regulations even for two-wheeled motorcycles that have not been previously regulated. Since it can be implemented only with software without additional hardware, the development cost is also low.

1 is a conceptual diagram of a 4-stroke engine misfire diagnosis system using a discrete Fourier transform according to an embodiment of the present invention.
2(a) and 2(b) are graphs showing changes in PSD values for crankshaft position sensor output signals during two engine cycles during normal ignition and misfire, respectively.
3 is a graph showing changes in PSD value and amplitude of engine speed during continuous misfire.
4 is a graph showing a change in engine speed when continuous misfire occurs.
Figure 5 is a flow chart for explaining the misfire diagnosis method of a single-stroke four-stroke 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 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.

Also, in this specification, the terms “include” or “have” are intended to indicate that there are features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and one or more other. It should be understood that features or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Further, terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components.

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

In the description with reference to the accompanying drawings, the same reference numerals will be assigned to the same components, and duplicate descriptions of the same components will be omitted. In the following description, when it is determined that the detailed description of known technologies related to the present invention may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

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

Among the terms used in describing the embodiment of the present invention, the section for the misfire analysis includes one engine cycle including the intake, compression, explosion, and exhaust strokes once, and another engine cycle having the same previous stroke. Means a section composed of a total of two consecutive engine cycles, and a section in which a real story analysis target section overlaps a section in which a previous real story analysis target section and an engine cycle are performed.

That is, one misfire analysis target section composed of two consecutive engine cycles and the preceding misfire analysis target section commonly include one engine cycle in the middle. This means that the first engine cycle of the two engine cycles in the current misfire analysis target section and the second engine cycle of the two engine cycles in the preceding misfire analysis target section are the same engine cycle.

For reference, one engine cycle means two wheels of the engine crankshaft (720° rotation, so one section analyzed by misfire consisting of two consecutive engine cycles means the engine crankshaft rotation of four wheels (1440°). do.

In addition, among the terms used in describing the embodiment of the present invention, the engine frequency is an engine calculated based on an engine speed for each stroke of a target section for misfire analysis (tooth time signal, which is an output signal of a crankshaft position sensor). It means that frequency components are extracted and rearranged into frequency waveforms by applying a discrete Fourier transform to the crankshaft rotation speed).

Here, the tooth time means the time required for the engine crankshaft to rotate at a certain angle.

And, among the terms used in describing an embodiment of the present invention, PSD is an abbreviation of power spectral density and is used as a meaning to indicate the energy distribution per unit frequency, and is used in the detailed description and drawings of the present invention. K means harmonic order.

1 is a conceptual diagram of a 4-stroke engine misfire diagnosis apparatus according to an embodiment of the present invention, with reference to FIG. 1, a description will be given of a 4-stroke engine misfire diagnosis system according to an embodiment of the present invention.

Referring to FIG. 1, a crankshaft position sensor 10 is disposed around a target wheel 40 on the engine crankshaft 30. 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 the crankshaft position sensor 20 when the target wheel 40 rotates The controller 20 calculates the angular velocity of the crankshaft 30 using the time information for detecting the tooth.

The controller 20 controls the engine speed by controlling the energization state of the fuel injector and the ignition coil in accordance with the driver's acceleration or deceleration request through hand accelerator operation (not shown), as well as controlling the output speed of the crankshaft position sensor (Tooth The time signal is diagnosed for misfire using the power spectral density (hereinafter abbreviated as'PSD') obtained by distributing the data to a discrete Fourier transform.

Misfire, as mentioned earlier, refers to a phenomenon in which fuel injected from an engine is not combusted but discharged into the outside air. When a misfire occurs, the periodicity of the output signal (Tooth time signal) that the crankshaft position sensor 20 detects and sends the tooth as no energy source accelerating the engine speed occurs in the explosion (or expansion) stroke. This is undermined.

Misfire appears as unburned fuel -> no combustion pressure -> reduced piston speed -> reduced crankshaft rotation momentum, resulting in increased output signal period and reduced engine speed. That is, when a misfire occurs, the engine speed decreases due to the absence of an energy source that drives the engine. Thus, analysis of the engine frequency characteristics obtained by converting the signal data output by the crankshaft position sensor 10 into a discrete Fourier transform results in diagnosis of the misfire. Can be.

The present invention focuses on the characteristics of engine frequencies that appear in different forms during normal ignition and misfire, and analyzes engine frequency characteristics of misfires occurring in a single-stroke four-stroke engine to accurately and quickly diagnose/detect the present invention. The misfire diagnosis system according to the embodiment includes a signal processing unit 22, a discrete Fourier transform unit 24, a PSD calculation unit 26, and a misfire diagnosis unit 28.

Hereinafter, the configuration of each part constituting the misfire diagnosis system of the single-stroke four-stroke engine according to the embodiment of the present invention will be described in more detail.

The main function of the signal processing unit 22 is down sampling. Specifically, the signal processing unit 22 down-samples the signal data output by the crankshaft position sensor 10 at regular intervals before discrete Fourier transformation of the signal data output by the crankshaft position sensor 10. This reduces the amount of signal data to be processed, thereby reducing the computational load to be borne by the controller.

For example, in the case where 36 teeth are formed on the outer circumferential surface of the target wheel 40, in order to diagnose engine misfire through engine frequency analysis, in the case of the method proposed in the present invention, two engine cycles, that is, a crankshaft 30 It is necessary to analyze the output signals of the 144 (36*4) crankshaft position sensors 10 for this 1440=720*2) rotating section. Therefore, the computational burden is greatly increased and the processing speed must be slowed down.

On the other hand, if, for example, a 1/3 down sampling process is performed through the signal processing unit 22, the number of processing is greatly reduced to 48, and the computational load is greatly reduced. That is, when the downsampling through the signal processing unit 22 is performed, the number of signals to be processed is greatly reduced and the computational load is reduced, so that a simple simplification of the computational process for signal processing can be achieved and the processing speed is also increased.

The signal processing unit 22 may downsample the signal data output by the crankshaft position sensor based on Nyquist's Sampling theory. For reference, the Nyquist sampling theory refers to the theory that all signals can be completely recorded by sampling at regular intervals with a frequency equal to twice the highest frequency included in the signal.

When the Nyquist sampling theory is applied to the engine misfire diagnosis system, it can be seen that the sampling frequency must be more than twice the engine frequency (F _sample ≥ 2F ₀ ) to realize engine speed without signal distortion. Here, F _sample means the sampling frequency, and F ₀ means the engine frequency.

[Table 1]

(단, L은 엔진의 기통수)로 표현될 수 있다. 본 발명에 따른 실시 예의 경우 단기통 엔진에 적용되므로 위 식에서 L 은 1이 된다. In [Table 1] above, the engine frequency is determined according to the engine speed and the engine cylinder, and the engine frequency according to the engine speed and the engine cylinder is

(However, L can be expressed as the number of cylinders of the engine). In the case of the embodiment according to the present invention, L is 1 in the above equation because it is applied to a single cylinder engine.

The signal data output from the crankshaft position sensor 10 down-sampled through the signal processing unit 22 is provided to the discrete Fourier transform unit 24, and the discrete Fourier transform unit 24 is included in the actual analysis target section 2 During four engine cycles, the signal data (down-sampled signal data) output by the crankshaft position sensor 10 is subjected to a discrete Fourier transform to extract frequency components and rearrange the extracted results into frequency waveforms.

The discrete Fourier transform unit 24 preferably removes a linear trend from the signal data output by the crankshaft position sensor during two engine cycles in one true analysis target section, and then based on the angular velocity of the crankshaft. The signal data output by the crankshaft position sensor is converted into frequency components. Here, since the discrete Fourier transform process is a known technique, a detailed description is omitted.

If the linear trend is not removed from the signal data output by the crankshaft position sensor 10, the increase or decrease in engine speed that may occur during the normal operation of the engine may affect the engine speed amplitude, which causes the engine frequency waveform. Sometimes it is difficult to accurately diagnose a true story by analyzing changes. Therefore, it is desirable to involve a linear trend elimination process.

The PSD calculating unit 26 calculates PSD from the discrete Fourier transformed frequency data through the discrete Fourier transform unit 24, and the calculated PSD value is provided to the true diagnosis unit 28. In addition, the misfire diagnosis unit 28 analyzes the PSD value provided by the PSD calculation unit to diagnose the misfire. For reference, PSD is an abbreviation of'power spectral density' and energy density per unit frequency.

The misfire diagnosis unit 28 analyzes the harmonic order value in which the maximum value of the power spectrum density calculated by the PSD calculation unit appears, and diagnoses the misfire. More specifically, the misfire diagnosis unit 28 diagnoses as a misfire when the maximum value of the PSD is displayed at a harmonic order value of 1, and as a normal ignition when the PSD value is maximized at a value other than 1 as the harmonic order value. .

2(a) and 2(b) are graphs showing changes in the PSD value for the crankshaft position sensor output signal during two engine cycles during normal ignition and misfire, respectively.

As shown in (a) of FIG. 2, in the case of normal ignition, the maximum value of PSD (power spectral density) appears when the harmonic order is 2 (k=2). This is because, in the case of normal ignition, frequency waveforms close to two sinusoids appear in two engine cycles included in the section to be analyzed.

On the other hand, when misfire occurs, the maximum value of PSD (power spectral density) appears when the harmonic order is 1 (k=1), as shown in FIG. 2(b). This is because when a misfire occurs, a discrete Fourier transform of the output signal of the crankshaft position sensor of the 2 cycles included in the misinterpretation target section results in a frequency waveform close to one sine wave as a whole.

The present invention pays attention to the fact that the harmonic order value in which the maximum value of the PSD for the crankshaft position sensor output signal for 2 cycles differs depending on whether misfire occurs, when the maximum value of the PSD appears when the harmonic order value is 1 It is diagnosed that engine misfire has occurred, and if the maximum value of PSD appears when the harmonic order value is not 1, the engine is diagnosed as having normal combustion.

The misfire diagnosis unit 28 also shows the maximum value of the PSD from the harmonic order value of 1 as a result of the discrete Fourier transform for two engine cycles in the current misinterpretation analysis target section, and the PSD value in the current misinterpretation analysis section If it is larger than the maximum value of the PSD of the misinterpretation target section diagnosed with the misfire immediately before, it is diagnosed that misfire has occurred continuously in two engine cycles.

The process of diagnosing whether a continuous misfire occurs by the misfire diagnosis unit will be described with reference to FIG. 3 later.

3 is a graph showing changes in PSD value and amplitude of engine speed during continuous misfire.

As mentioned before, in the case of normal ignition, since the frequency waveforms close to the two sine waves appear in the two engine cycles included in the realization analysis target section, the maximum value of the PSD appears at the harmonic order value of 2 (k=2) (Fig. 3(a)), the maximum value of the PSD appears at a harmonic order value of 1 (k=1) because only one frequency waveform appears near the sinusoidal wave in two engine cycles at the time of misfire (Fig. 3(b)). .

In addition, when a misfire occurs continuously in two engine cycles in a section to be analyzed for misfire, since there is no continuous addition of energy due to explosion in the explosion stroke of the two engine cycles, as shown in FIG. Likewise, the amplitude of the initial engine speed and the end engine speed in one misfire analysis target section composed of two engine cycles becomes larger than the amplitude in a single misfire.

The fact that the amplitude of the engine speed becomes larger in one misinterpretation target section due to the continuous misfire means that the PSD value becomes larger than in the case of a single misfire in another sense. According to the present invention, the PSD value of k1 in the current section (#3 in FIG. 3) is compared to the PSD value in k1 in the previous section (#2 in FIG. 3) diagnosed as a true story by using the characteristics of the PSD value that appears during continuous misfire. If it is large, it is diagnosed by continuous misfire.

As another method for the diagnosis of continuous misfire, a method using a difference in engine speed between the beginning of the explosive stroke of the engine cycle and the end of the exhaust stroke may be considered. If the engine speed at the end of the exhaust stroke is smaller than the engine speed at the beginning of the explosive stroke in the first engine cycle among the two cycles in the section to be analyzed, the diagnosis is made as continuous misfire. Concept.

4 is a graph showing engine speed change when continuous misfire occurs.

Misfire is that no energy source accelerates engine speed in an explosive stroke. Therefore, as shown in FIG. 4, the engine speed of the second engine cycle is naturally reduced compared to the first engine cycle, and compared to the engine speed at the beginning of the explosive stroke of the second engine cycle (rpm 1_engine speed at the top dead center of the explosive stroke). The engine speed at the end of the exhaust stroke (rpm 2_the engine speed at the top dead center at the end of the exhaust stroke) also becomes small.

Therefore, by using the characteristics of changes in engine speed generated during continuous misfire, it is possible to clearly diagnose whether continuous misfire occurs for two engine cycles in one misfire analysis target section.

On the other hand, when the misfire is diagnosed, the above-described controller, for example, the ECU, may include a control logic that switches the misfire flag (Flag _mist ) to True, and returns the misfire flag (Flag _mist ) to False when it returns to normal. .

Hereinafter, the misfire diagnosis process in the single-stroke four-stroke engine performed by the misfire diagnosis apparatus of the single-cylinder four-stroke engine utilizing the discrete Fourier transform will be described with reference to the flowchart of FIG. 5.

5 is a flowchart illustrating a method for diagnosing misfires in a single-stroke four-stroke engine according to an embodiment of the present invention.

5, the misfire diagnosis method in the single-stroke four-stroke engine according to an embodiment of the present invention includes a data collection step (S100) and a down sampling step (S200). In the data collection step (S100), the signal data output by the crankshaft position sensor during two engine cycles is collected, and in the down-sampling step (S200), down-sampling is performed on the signal data collected in the data collection step.

In the down sampling step (S200), specifically, the signal data by the crankshaft position sensor during the two engine cycles collected in the data collection step (S100), which is the previous step, is down-sampled at regular intervals and processed. Reduce the amount of signal data to be done. Accordingly, the computational load to be borne by the controller can be reduced and the processing speed can be improved.

The signal data for the two engine cycles down-sampled through the S200 step is rearranged into an engine frequency form through a discrete Fourier transform step (S300). That is, in the discrete Fourier transform step (S300), a frequency component is extracted by applying a discrete Fourier transform to the engine speed extracted from the signal output from the crankshaft position sensor, and the rearranged result is rearranged into a frequency waveform. .

In step S300, the linear trend is preferably removed from the signal data output by the crankshaft position sensor during two engine cycles in one misinterpretation target section, and then the crankshaft position sensor is based on the angular velocity of the crankshaft. Converts the signal data output by the frequency component. As mentioned earlier, the discrete Fourier transform process is a known technique, and thus its description is omitted.

The misdiagnosis method according to an embodiment of the present invention also includes a PSD calculating step (S400) for calculating the power spectrum density (PSD) from the frequency data discretely Fourier transformed in step S300 after the S300 step, and the PSD calculating step (S400). It includes a misfire diagnosis step (S500) for diagnosing the misfire by analyzing the harmonic order value showing the maximum value of the PSD calculated in ).

In the misfire diagnosis step (S500) applied to the misfire diagnosis method of the single-stroke four-stroke engine according to an embodiment of the present invention, specifically, the maximum value of the power spectral density at a value (k)1) other than the harmonic order value is 1 When it appears, it is diagnosed as normal ignition, and when the harmonic order value is 1 (k=1), when the maximum value of the power spectral density appears, it is diagnosed that misfire has occurred.

As mentioned before, in the case of normal ignition, since the frequency waveforms close to the two sine waves appear in the two engine cycles included in the realization analysis target section, the harmonic order value of PSD, the concept corresponding to the speed amplitude, is 2 (k=2). This is because the maximum value appears, but only one frequency waveform close to a sinusoidal wave appears in two engine cycles at the time of misfire, so that the maximum value of the PSD appears at a harmonic order value of 1 (k=1).

In the misfire diagnosis step (S500), the maximum value of the PSD from the harmonic order value of 1 is shown as the result of the discrete Fourier transform for the two engine cycles in the current misinterpretation analysis target section, and the PSD value in the current misinterpretation analysis section If it is larger than the maximum value of the PSD of the misinterpretation target section diagnosed with the misfire immediately before, it is diagnosed that misfire has occurred continuously in two engine cycles.

If a misfire occurs continuously in two engine cycles in one misfire analysis target section, there is no continuous addition of energy due to an explosion in the explosion stroke of two engine cycles, so within one misfire analysis target section composed of two engine cycles The amplitudes of the initial engine speed and the late engine speed must be greater than the amplitude in a single misfire.

The fact that the amplitude of the engine speed becomes larger in one misinterpretation target section due to the continuous misfire means that the PSD value becomes larger than in the case of a single misfire in another sense. Therefore, if the PSD value of k1 in the current true story analysis target section is larger than the PSD value of k1 in the previous true story analysis target section diagnosed as a true story, it is diagnosed as continuous true story according to the characteristics of the PSD value displayed during continuous true story.

As another example for continuous misfire diagnosis, among two engine cycles included in one misfire analysis target section, even if the engine speed at the end of the exhaust stroke is smaller than the initial engine speed of the second engine cycle, it is diagnosed as continuous misfire. can do.

When a continuous misfire occurs, the engine speed of the second engine cycle is naturally reduced compared to the first engine cycle in a section subject to a misfire analysis, and the engine speed at the beginning of the explosive stroke of the second engine cycle (explosive stroke initial boss) This is because the engine speed at the end of the exhaust stroke (engine speed at the top dead center at the end of the exhaust stroke) is smaller than the engine speed at the point).

According to the misfire diagnosis method of the single-stroke four-stroke engine according to the embodiment of the present invention, a discrete Fourier transform is applied to the engine speed for each stroke of a section to be analyzed to quantify it in the form of an engine frequency, and the mismatch analysis subject to the discrete Fourier transform It is configured to diagnose whether the normal ignition or misfire (Misfire) by analyzing the engine frequency of the section.

In other words, it is a method to diagnose/detect a true story with only the minimum key information that can clearly determine whether it is true. It is possible to provide an optimized misfire detection function suitable for the situation of a two-wheeled motorcycle using a low-cost ECU compared to an expensive ECU.

As a result, in the global trend of exhaust emission regulations being strengthened day by day, it is possible to meet the market demand to meet the emission regulations even for two-wheeled motorcycles that have not been previously regulated. Since it can be implemented only with software without additional hardware, the development cost is also low.

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

10: crankshaft position sensor
20: controller
22: signal processing unit
24: discrete Fourier transform
26: PSD calculation unit
28: true story diagnosis
30: crankshaft
40: target wheel

Claims (14)

As a method of diagnosing misfires occurring in a single-stroke four-stroke engine using the output signal of a crankshaft position sensor,
a) a data collection step of collecting signal data output by the crankshaft position sensor during two engine cycles;
b) a discrete Fourier transform step of quantifying a frequency form by applying a discrete Fourier transform to signal data for two engine cycles collected in the data collecting step;
c) a PSD calculation step of calculating a power spectrum density (PSD) from the frequency data converted in the discrete Fourier transform step; And
d) a misfire diagnosis step of diagnosing misfire by analyzing a harmonic order value in which the maximum value of the power spectral density calculated in the PSD calculation step appears; includes,
The two consecutive engine cycles constitute one misfire analysis target section, and one misfire analysis target section overlaps the preceding misfire analysis target section and one engine cycle, and the misfire diagnosis method of the short-term four-stroke engine is characterized. .
According to claim 1,
The discrete Fourier transform step,
After removing the linear trend from the crankshaft position sensor output signal data during the two engine cycles collected in the data collection step, converting the crankshaft position sensor output signal data into frequency components based on the angular velocity of the crankshaft. Misdiagnosis method of single-stroke four-stroke engine.
According to claim 1,
In the misfire diagnosis step,
When the harmonic order value is not 1, when the maximum value of the power spectral density appears, it is diagnosed as normal ignition.
According to claim 1,
In the misfire diagnosis step,
A method for diagnosing misfires in a single-stroke four-stroke engine, characterized in that, when the harmonic order value is 1, the maximum value of the power spectral density appears.
According to claim 1,
In the misfire diagnosis step,
If the harmonic order value is the maximum value of the power spectrum density at 1, and the maximum value of the power spectrum density at which the harmonic order value is 1 is greater than the maximum value of the power spectrum density of the section of the true story analyzed as the previous true story, A method for diagnosing misfire of a single-stroke four-stroke engine, characterized in that the engine is diagnosed as having a misfire continuously in two engine cycles.
According to claim 1,
In the misfire diagnosis step,
A single-cylinder four-stroke engine characterized by diagnosing continuous engine misfire if the engine speed at the end of the exhaust stroke is less than the initial engine speed of the second engine cycle among the two engine cycles included in one misfire analysis target section. How to diagnose misfire.
According to claim 1,
a') Down sampling step of down-sampling the signal data by the crankshaft position sensor for two engine cycles collected in the data collection step prior to the discrete Fourier transform step at regular intervals. How to diagnose misfires in 4-stroke engines.
A system for diagnosing misfires occurring in a single-stroke four-stroke engine using the output signal of a crankshaft position sensor.
A discrete Fourier transform unit converting the signal data output by the crankshaft position sensor during two engine cycles into a discrete Fourier transform;
A PSD calculating unit calculating a power spectral density (PSD) from the discrete Fourier transformed frequency data through the discrete Fourier transform unit;
Includes; a misdiagnosis diagnosis unit for diagnosing a misfire by analyzing a harmonic order value in which the maximum value of the power spectrum density calculated by the PSD calculation unit appears;
The two consecutive engine cycles constitute one misfire analysis target section, and one misfire analysis target section is a misfire diagnosis system for a short-term four-stroke engine, characterized in that the preceding misfire analysis target section and one engine cycle overlap. .
The method of claim 8,
Further comprising a signal processing unit for down-sampling (Down sampling) the signal data output from the crankshaft position sensor prior to the discrete Fourier transform through the discrete Fourier transform section; misfire diagnosis system of a single-stroke four-stroke engine.
The method of claim 8,
The discrete Fourier transform unit,
Short-term box 4 characterized in that after removing the linear trend from the signal data output by the crankshaft position sensor during the two engine cycles, the signal data output by the crankshaft position sensor is converted into a frequency component based on the angular velocity of the crankshaft. Misdiagnosis system of stroke engine.
The method of claim 8,
The misfire diagnosis unit,
A misfire diagnosis system of a single-stroke four-stroke engine, characterized in that when the maximum value of the power spectrum density appears at a value other than 1, the harmonic order value is diagnosed as normal ignition.
The method of claim 8,
The misfire diagnosis unit,
A misfire diagnosis system of a single-stroke four-stroke engine, characterized in that, when the harmonic order value is 1, the maximum value of the power spectral density appears, diagnosis of misfire has occurred.
The method of claim 8,
The misfire diagnosis unit,
If the harmonic order value is the maximum value of the power spectrum density at 1, and the maximum value of the power spectrum density at which the harmonic order value is 1 is greater than the maximum value of the power spectrum density of the section of the true story analyzed as the previous true story, A misfire diagnosis system for a single-stroke four-stroke engine, characterized in that the misfire is continuously diagnosed in two engine cycles.
The method of claim 8,
The misfire diagnosis unit,
A single-cylinder four-stroke engine characterized by diagnosing continuous engine misfire if the engine speed at the end of the exhaust stroke is less than the initial engine speed of the second engine cycle among the two engine cycles included in one misfire analysis target section. True story diagnosis system.

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