Patent Description:
The present application claims priority based on <CIT>.

In the related art, a misfire detecting device for detecting a misfire of an internal combustion engine is known. For example, a misfire detecting device disclosed in PTL <NUM> frequency-analyzes an engine angular acceleration acquired based on a detection result of a crank angle sensor. Further, the misfire detecting device individually determines, for each of cylinders, whether or not an inter-cylinder component of angular acceleration (a component corresponding to a cycle obtained by dividing one combustion cycle of an internal combustion engine by the number of cylinders of the internal combustion engine) is smaller than a threshold value based on a result of frequency analysis. Accordingly, the misfire detecting device determines whether or not a misfire has occurred in any one of a plurality of cylinders configuring the internal combustion engine.

Other examples of internal combustion engine misfire detecting devices and methods are disclosed by <CIT> and <CIT>.

Since whether the misfire detecting device individually determines whether a misfire has occurred for each of the plurality of cylinders configuring the internal combustion engine, there is a possibility that it takes time to detect an all-cylinder misfire. As a result, there is a concern that the amount of non-combustion gas increases in response to occurrence of the all-cylinder misfire. For example, since the number of cylinders is large in a case where the internal combustion engine is a power generation engine, there is a concern that detection of the all-cylinder misfire is delayed and a large amount of non-combustion gas is generated.

An object of the present disclosure is to provide an internal combustion engine misfire detecting device and a misfire detecting method that can more quickly detect an all-cylinder misfire.

According to at least one embodiment of the present disclosure, there is provided an internal combustion engine misfire detecting device,.

The internal combustion engine misfire detecting device for detecting a misfire of an internal combustion engine having a plurality of cylinders, including:.

According to at least one embodiment of the present disclosure, there is provided an internal combustion engine misfire detecting method,.

The internal combustion engine misfire detecting method for detecting a misfire of an internal combustion engine having a plurality of cylinders, including:.

With the present disclosure, the internal combustion engine misfire detecting device and the misfire detecting method that can more quickly detect an all-cylinder misfire can be provided.

Hereinafter, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, dimensions, materials, shapes, and relative disposition of configuring components described in the embodiments or shown in the drawings are not intended to limit the scope of the present disclosure but are merely explanatory examples.

For example, an expression representing a relative or absolute disposition, such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric", and "coaxial", does not strictly represent only such a disposition, but also represents a state of being relatively displaced with a tolerance or with an angle or a distance to the extent that the same function can be obtained.

For example, an expression representing that objects are in an equal state, such as "identical", "equal", and "homogeneous", does not strictly represent only an equal state but also represents a state where there is a tolerance or a difference to the extent that the same function can be obtained.

For example, an expression representing a shape, such as a quadrangular shape and a cylindrical shape, does not represent only a shape such as a quadrangular shape and a cylindrical shape in a geometrically strict sense, but also represents a shape including an uneven portion, and a chamfered portion within a range in which the same effect can be obtained.

On the other hand, expressions, such as "comprising", "including", and "having" one component, are not exclusive expressions excluding the presence of other components.

The same configurations will be assigned with the same reference signs, and description thereof will be omitted in some cases.

<FIG> is a conceptual diagram showing a schematic configuration of a misfire detecting system according to an embodiment of the present disclosure. In some embodiments, a misfire detecting system <NUM> includes an internal combustion engine <NUM> and an internal combustion engine misfire detecting device <NUM> (hereinafter, simply referred to as a "misfire detecting device <NUM>" in some cases). Hereinafter, examples of schematic configurations of the internal combustion engine <NUM> and the misfire detecting device <NUM> will be given.

The internal combustion engine <NUM> of the present example is a power generation gas engine that drives a generator by making a combustible gas supplied to each cylinder <NUM> combust. The internal combustion engine <NUM> has a plurality of cylinders <NUM>. The number of the cylinders <NUM> may be any number such as four, eight, and sixteen. Each of the cylinders <NUM> communicates with an intake pipe <NUM> via an intake manifold <NUM> and communicates with an exhaust pipe <NUM> via an exhaust manifold <NUM>. In addition, the internal combustion engine <NUM> is provided with a turbocharger <NUM> that has a compressor <NUM> provided at the intake pipe <NUM> and a turbine <NUM> provided at the exhaust pipe <NUM>. The compressor <NUM> is configured to supply a compressed gas to each of the cylinders <NUM>. The turbine <NUM> is configured to be rotated together with the compressor <NUM> by an exhaust gas exhausted from each of the plurality of cylinders <NUM>.

In the present specification, the exhaust gas is a concept including a combustion gas and a non-combustion gas.

After being supplied to an inside of each of the cylinders <NUM>, a combustible gas flowing in the intake pipe <NUM> combusts in response to ignition by an ignition plug <NUM>. With the generation of a combustion gas, power is extracted, and a crank shaft (not shown) rotates. An exhaust gas exhausted from each of the cylinders <NUM> flows to the turbine <NUM> via the exhaust pipe <NUM>.

In addition, ignition in each of the cylinders <NUM> is controlled by an ECU <NUM>. Specifically, as the ECU <NUM> sends an ignition instruction signal to an ignition device <NUM>, ignition by the ignition plug <NUM> is performed. When ignition is normally performed in each of the plurality of cylinders <NUM>, the crank shaft is rotated at a specific rotation speed by power extracted in turn in each of the cylinders <NUM>. Although one ignition plug <NUM> is shown in <FIG> which is a conceptual diagram, each of a plurality of ignition plugs <NUM> may be provided inside each of the cylinders <NUM>.

The ECU <NUM> is configured by a computer and includes a processor, a memory, and an external communication interface. The processor is a CPU, a GPU, an MPU, a DSP, a combination thereof, or the like. The processor may be realized by an integrated circuit such as a PLD, an ASIC, a FPGA, and an MCU. The memory is configured to temporarily or non-temporarily store various types of data and is realized by, for example, a RAM, a ROM, a flash memory, or a combination thereof. As the processor processes data in accordance with a command of a program loaded in the memory, various types of control signals, such as an ignition instruction signal to be sent to the ignition device <NUM>, are generated.

In the shown embodiment, the ECU <NUM> is electrically connected to a crank angle sensor <NUM>, a turbo rotation speed sensor <NUM>, a turbine pressure sensor <NUM>, and each of a plurality of exhaust gas temperature sensors <NUM>. However, for convenience of making the drawing easier to see, only the crank angle sensor <NUM> of the sensors is shown to be connected to the ECU <NUM> in <FIG> which is a conceptual diagram. The crank angle sensor <NUM> is configured to acquire a rotation angle of a crank shaft of the internal combustion engine <NUM>. Therefore, the ECU <NUM> can acquire an engine rotation speed of the internal combustion engine <NUM> based on a detection result of the crank angle sensor <NUM>. The turbo rotation speed sensor <NUM> is configured to detect a turbo rotation speed which is a rotation speed of the turbocharger <NUM>. The turbine pressure sensor <NUM> is configured to detect an inlet exhaust gas pressure of the turbine <NUM> (that is, a pressure of an exhaust gas flowing into the turbine <NUM>). The plurality of exhaust gas temperature sensors <NUM> are provided corresponding to the plurality of cylinders <NUM> respectively. Each of the exhaust gas temperature sensors <NUM> is configured to detect the temperature of an exhaust gas exhausted from the corresponding cylinder <NUM>.

In other embodiments, any sensor of the crank angle sensor <NUM>, the turbo rotation speed sensor <NUM>, the turbine pressure sensor <NUM>, and the exhaust gas temperature sensor <NUM> may not be provided. For example, the crank angle sensor <NUM> and the turbo rotation speed sensor <NUM> may be provided, and any of the other sensors may not be provided. Alternatively, the turbo rotation speed sensor <NUM> and the turbine pressure sensor <NUM> may be provided, and any of the other sensors may not be provided.

The ECU <NUM> according to the embodiment of the present disclosure includes the misfire detecting device <NUM>. The misfire detecting device <NUM> is configured to detect a misfire in the internal combustion engine <NUM>. As a more specific example, the misfire detecting device <NUM> is configured to detect an all-cylinder misfire, which is a misfire in all of the plurality of cylinders <NUM>, and a partial misfire, which is a misfire only in any one cylinder <NUM> of the plurality of cylinders <NUM>. The partial misfire is a concept including a misfire (one-cylinder misfire) that occurs only in any one of the plurality of cylinders <NUM> and a misfire that occurs only in any plurality of cylinders <NUM>. In other embodiments, the misfire detecting device <NUM> may not detect a partial misfire.

The concepts of the internal combustion engine <NUM> and the misfire detecting device <NUM> have been described hereinbefore. Hereinafter, as an example of some embodiments of the present disclosure, a misfire detecting device 10A (<NUM>) according to a first embodiment and a misfire detecting device 10B (<NUM>) according to a second embodiment will be described in detail in turn.

<FIG> is a conceptual diagram showing a configuration of the misfire detecting device according to the first embodiment of the present disclosure. The misfire detecting device 10A (<NUM>) includes a pulsating component acquisition unit <NUM>, a difference parameter acquisition unit <NUM>, and a misfire determination unit 40A (<NUM>).

The pulsating component acquisition unit <NUM> is configured to frequency-analyze operation parameter data <NUM> (see <FIG>) indicating a change over time in an operation parameter and to acquire a pulsating component spectrum Sp (see <FIG>) which is a spectrum at a frequency of pulsation of the internal combustion engine <NUM>. The operation parameter is a parameter correlated with an overall operation status of the plurality of cylinders <NUM> (a specific example to be described later). For this reason, the operation parameter changes depending on presence or absence of pulsation and a degree of pulsation of the internal combustion engine <NUM>. Frequency-analysis performed on the operation parameter data <NUM> is FFT, BPF, short-term Fourier transform (STFT) or the like.

The operation parameter is, for example, an engine rotation speed, an inlet exhaust gas pressure of the turbine <NUM>, a turbo rotation speed, or the like. The pulsating component acquisition unit <NUM> acquires the operation parameter data <NUM> by continuously acquiring a detection result of the crank angle sensor <NUM>, the turbo rotation speed sensor <NUM>, or the turbine pressure sensor <NUM>.

<FIG> is a graph conceptually showing operation parameter data according to the embodiment of the present disclosure. Operation parameter data 61A (<NUM>) shows a case where all of the plurality of cylinders <NUM> operate normally without a misfire. The operation parameter at this time repeats a periodic change. Operation parameter data 61B (<NUM>) shows a case where a partial misfire has occurred in the internal combustion engine <NUM> (a one-cylinder misfire is given as an example in <FIG>). In the operation parameter in this case, an ideal change in the operation parameter does not occur at a timing when combustion is supposed to occur in the misfired cylinder <NUM> (t = ta). Operation parameter data 61C (<NUM>) shows a case where an all-cylinder misfire has occurred in the internal combustion engine <NUM>. In the operation parameter in this case, a periodic change in the operation parameter rarely occurs after a timing when the all-cylinder misfire has occurred (t ≧ ta). Therefore, when any one of the all-cylinder misfire and the partial misfire occurs, the pulsating component spectrum Sp described above significantly reduces (see <FIG>).

<FIG> is a graph conceptually showing a result of performing short-term Fourier transform on operation parameter data according to the embodiment of the present disclosure. More specifically, in <FIG>, a result of performing short-term Fourier transform on the operation parameter data 61C when an all-cylinder misfire occurs is given as an example.

On the vertical axis of the graph shown in <FIG>, fcyl indicates a frequency of pulsation of the internal combustion engine <NUM>. There is no problem even when fcyl deviates from an ideal value identified through a calculation formula, and a frequency at which a strong spectrum appears through frequency-analysis may be regarded as a frequency of pulsation. This is because the actual measured value deviates from the ideal value due to some factors during measurement.

As can be seen from <FIG>, in a case where an all-cylinder misfire has occurred at a specific timing (t = ta), the pulsating component spectrum Sp disappears or almost disappears. Although details are not shown, the pulsating component spectrum Sp significantly decreases also in a case where a partial misfire has occurred. Therefore, it is possible to determine that an all-cylinder misfire or a partial misfire has occurred in the internal combustion engine <NUM> based on the pulsating component spectrum Sp. Hereinafter, a threshold value that is reference of the determination will be referred to as a first threshold value. The first threshold value may be identified through an experiment, may be identified through simulation or analysis, or may be identified through a combination thereof (the same also applies to a second threshold value, a third threshold value, a fourth threshold value, and a fifth threshold value to be described later).

Referring back to <FIG>, the difference parameter acquisition unit <NUM> is configured to acquire a difference parameter correlated with a degree of a difference (variations) in each of operations of the plurality of cylinders <NUM>. A specific example of the difference parameter will be described later. When an all-cylinder misfire occurs, none of the plurality of cylinders <NUM> operates normally, so that the difference parameter becomes small. As a result, the difference parameter at this time falls below a specific threshold value (hereinafter, referred to as the second threshold value). Also in a case where all of the plurality of cylinders <NUM> operate normally, similarly, the difference parameter is small and falls below the second threshold value. On the other hand, when a partial misfire occurs, any one of the plurality of cylinders <NUM> operates normally, and the remaining cylinders <NUM> do not operate normally. Therefore, the difference parameter at this time is large compared to a time when an all-cylinder misfire has occurred and a time of a normal operation when a misfire has not occurred and is equal to or larger than a specific threshold value (hereinafter, referred to as the third threshold value). The third threshold value is a value that is equal to or larger than the second threshold value, and an embodiment in which the third threshold value and the second threshold value are values identical to each other is not excluded.

<FIG> is a matrix showing a relationship between a pulsating component spectrum, a difference parameter, an all-cylinder misfire, and a partial misfire according to the embodiment of the present disclosure. As described above, when the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> is equal to or larger than the first threshold value, it can be determined that an all-cylinder misfire and a partial misfire have not occurred. Thus, in a case where the difference parameter at this time falls below the second threshold value, it can be determined that all of the plurality of cylinders <NUM> operate normally. On the other hand, in a case where the pulsating component spectrum Sp falls below the first threshold value, it can be determined that an all-cylinder misfire or a partial misfire has occurred. In this case, further, when the difference parameter acquired by the difference parameter acquisition unit <NUM> falls below the second threshold value, it can be determined that an all-cylinder misfire has occurred, and when the difference parameter is equal to or larger than the third threshold value, it can be determined that a partial misfire has occurred.

The misfire determination unit 40A (<NUM>) shown in <FIG> includes an all-cylinder misfire determination unit 41A (<NUM>). The all-cylinder misfire determination unit 41A is configured to determine occurrence of an all-cylinder misfire in the internal combustion engine <NUM> in accordance with the reference described above using <FIG>. That is, an all-cylinder misfire determination unit <NUM> is configured to determine that an all-cylinder misfire has occurred in the internal combustion engine <NUM> in a case where a spectrum acquired by the pulsating component acquisition unit <NUM> falls below the first threshold value and a difference parameter acquired by the difference parameter acquisition unit <NUM> falls below the second threshold value.

With the configuration, in a case where the pulsating component spectrum Sp falls below the first threshold value and a difference parameter falls below the second threshold value, the all-cylinder misfire determination unit 41A determines that an all-cylinder misfire has occurred. Since it is not necessary to individually determine whether a misfire has occurred in each of the plurality of cylinders <NUM>, the misfire detecting device 10A can more quickly detect occurrence of an all-cylinder misfire. For example, in a case where the internal combustion engine <NUM> is applied to a power generation engine in which the number of the cylinders <NUM> is <NUM> or more, the number of the cylinders <NUM> tends to increase, and a large amount of non-combustion gas can be generated when an all-cylinder misfire occurs compared to a case where the internal combustion engine <NUM> is applied as a vehicle engine. In this point, as the all-cylinder misfire determination unit 41A quickly determines occurrence of an all-cylinder misfire as in the present disclosure, it is possible to perform appropriate processing before a large amount of non-combustion gas is generated.

In other embodiments, in a case where a spectrum acquired by the pulsating component acquisition unit <NUM> is equal to or larger than the first threshold value and a difference parameter acquired by the difference parameter acquisition unit <NUM> falls below the second threshold value, the all-cylinder misfire determination unit 41A may determine that the internal combustion engine <NUM> operates normally.

In the embodiment given as an example in <FIG>, the misfire determination unit 40A (<NUM>) includes a partial misfire determination unit 42A (<NUM>). The partial misfire determination unit 42A is configured to determine occurrence of a partial misfire in the internal combustion engine <NUM> in accordance with the reference described above using <FIG>. Specifically, the partial misfire determination unit 42A is configured to determine that a partial misfire has occurred in the internal combustion engine <NUM> in a case where the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> falls below the first threshold value and a difference parameter acquired by the difference parameter acquisition unit <NUM> is equal to or larger than the third threshold value.

With the configuration, the misfire detecting device 10A can identify whether a misfire which has occurred in the internal combustion engine <NUM> is a partial misfire or an all-cylinder misfire with high accuracy as the partial misfire determination unit 42A and the all-cylinder misfire determination unit 41A are included.

A first example of details of the difference parameter acquisition unit <NUM> will be described with reference to <FIG> and <FIG> is a graph conceptually showing a result of performing short-term Fourier transform on target data according to the embodiment of the present disclosure.

The difference parameter acquisition unit <NUM> is configured to frequency-analyze target data indicating a change over time in a sensor value detected by a single sensor. The single sensor is, for example, the crank angle sensor <NUM>, the turbo rotation speed sensor <NUM>, or the turbine pressure sensor <NUM>. Therefore, the sensor value in this case is an engine rotation speed, a turbo rotation speed, or an inlet exhaust gas pressure of the turbine <NUM>. Therefore, the sensor value acquired by the difference parameter acquisition unit <NUM> may be the same as the operation parameter acquired by the pulsating component acquisition unit <NUM> described above. All of the sensor values is correlated with a degree of a difference in an operation of each of the plurality of cylinders <NUM>. The correlation becomes clearer by frequency-analyzing target data indicating a change over time in a sensor value. Thus, the difference parameter acquisition unit <NUM> is configured to frequency-analyze target data and to acquire a cycle component spectrum Sc (see <FIG>) which is a spectrum at a frequency for one cycle of the internal combustion engine <NUM> as a difference parameter. For example, one cycle of the internal combustion engine <NUM> functioning as a four-cycle engine completes each time the internal combustion engine <NUM> makes two rotations, and for example, one cycle of the internal combustion engine <NUM> functioning as a two-cycle engine completes each time the internal combustion engine <NUM> makes one rotation.

The graph given as an example in <FIG> shows a spectrum when an all-cylinder misfire occurs as in <FIG>. In addition, fNe at the vertical axis of the graph of <FIG> is a frequency corresponding to one cycle of the internal combustion engine <NUM>. fNe may deviate from an ideal value acquired through calculation, like fcyl. When an all-cylinder misfire occurs (t = ta), a sensor value rarely changes periodically (not shown), and the cycle component spectrum Sc disappears or almost disappears (falls below the second threshold value). Although details are not shown, since periodic changes partially occur in the sensor value when a partial misfire occurs, the cycle component spectrum Sc is equal to or larger than the third threshold value.

Therefore, in the first example, the all-cylinder misfire determination unit 41A can determine that an all-cylinder misfire has occurred in a case where the pulsating component spectrum Sp falls below the first threshold value and the cycle component spectrum Sc falls below the second threshold value. In addition, the partial misfire determination unit 42A can determine that a partial misfire has occurred in a case where the pulsating component spectrum Sp falls below the first threshold value and the cycle component spectrum Sc is equal to or larger than the third threshold value.

With the configuration, the all-cylinder misfire determination unit 41A can determine whether an all-cylinder misfire has occurred based on the cycle component spectrum Sc. In addition, since the cycle component spectrum Sc, which is difference data, is acquired based on a sensor value detected by a single sensor, the cycle component spectrum Sc is detected with a simpler configuration. Accordingly, a configuration for detecting occurrence of an all-cylinder misfire can be made simpler. In addition, for the same reason, a configuration for detecting occurrence of a partial misfire can be made simpler.

In the embodiment of the present disclosure, the sensor value described above is identical to an operation parameter, and target data indicating a change over time in the sensor value is identical to the operation parameter data <NUM> (see <FIG>). That is, the operation parameter data <NUM> is frequency-analyzed by both of the pulsating component acquisition unit <NUM> and the difference parameter acquisition unit <NUM>. In this case, the graph shown in <FIG> can be superimposed and reflected on the graph shown in <FIG>. With the configuration, as data is frequency-analyzed based on the sensor value detected by a single sensor, both of the pulsating component spectrum Sp and the cycle component spectrum Sc are acquired. Accordingly, a configuration for detecting occurrence of an all-cylinder misfire can be made simpler. In addition, for the same reason, a configuration for detecting occurrence of a partial misfire can be made simpler.

An operation parameter according to the embodiment of the present disclosure is a sensor value of the turbo rotation speed sensor <NUM> or the turbine pressure sensor <NUM>. That is, the sensor value described above is a turbine rotation speed or an inlet exhaust gas pressure of the turbine <NUM>. The two sensor values quickly respond to an all-cylinder misfire that occurs in the internal combustion engine <NUM>. That is, when an all-cylinder misfire occurs in the internal combustion engine <NUM>, the pulsating component spectrum Sp responds (decreases) relatively quickly based on any one of the two sensor values. Accordingly, with the configuration, the misfire detecting device 10A can more quickly detect occurrence of an all-cylinder misfire. In addition, in the embodiment in which the sensor value described above is identical to the operation parameter, the misfire detecting device <NUM> can also more quickly detect a partial misfire.

A second example of details of the difference parameter acquisition unit <NUM> will be described with reference to <FIG>, <FIG>, and <FIG> is a graph conceptually showing a relationship between detection results of a plurality of cylinder sensors <NUM> and a difference parameter according to the embodiment of the present disclosure.

In the second example, instead of using a single sensor as in the first example, a plurality of sensors are used. As a specific example, the difference parameter acquisition unit <NUM> is configured to analyze a sensor value detected by each of the plurality of cylinder sensors <NUM> and to acquire a difference parameter. Each of the plurality of cylinder sensors <NUM> is configured to detect an operation state of each of the plurality of cylinders <NUM>. In the embodiment given as an example in <FIG>, the cylinder sensor <NUM> is the exhaust gas temperature sensor <NUM>, and the sensor value is a temperature of an exhaust gas in the cylinder <NUM>. That is, the difference parameter acquisition unit <NUM> of the present example is configured to analyze the temperature of the exhaust gas, which is detected by each of the plurality of exhaust gas temperature sensors <NUM>.

Therefore, the all-cylinder misfire determination unit 41A can determine that an all-cylinder misfire has occurred in a case where the pulsating component spectrum Sp falls below the first threshold value and a difference parameter based on each of detection results of the plurality of cylinder sensors <NUM> falls below the second threshold value. In addition, the partial misfire determination unit 42A can determine that a partial misfire has occurred in a case where the pulsating component spectrum Sp falls below the first threshold value and the difference parameter is equal to or larger than the third threshold value.

With the configuration, a difference parameter acquired based on each of detection results of the plurality of cylinder sensors <NUM> is strongly correlated with a degree of a difference in an operation of each of the plurality of cylinders <NUM>. Therefore, the difference parameter greatly changes depending on whether any one of an all-cylinder misfire and a partial misfire occurs. Accordingly, the all-cylinder misfire determination unit 41A can detect an all-cylinder misfire in the internal combustion engine <NUM> with higher accuracy. In addition, based on the detection results of the cylinder sensors <NUM>, which are the exhaust gas temperature sensors <NUM>, the all-cylinder misfire determination unit 41A determines whether an all-cylinder misfire has occurred in the internal combustion engine <NUM>. Detection results of the exhaust gas temperature sensors <NUM> can easily reflect a difference in operations of the plurality of cylinders <NUM>. Accordingly, the misfire determination unit 40A can accurately detect occurrence of an all-cylinder misfire. In addition, whether the occurred misfire is an all-cylinder misfire or a partial misfire can also be accurately identified.

In other embodiments, the plurality of cylinder sensors <NUM> may be configured to detect an exhaust gas pressure or an exhaust gas flow rate of the corresponding cylinder <NUM>. Even in this case, since a difference parameter acquired based on each of detection results of the plurality of cylinder sensors <NUM> is strongly correlated with a degree of a difference in an operation of each of the plurality of cylinders <NUM>, an all-cylinder misfire in the internal combustion engine <NUM> can be detected with high accuracy. In addition, whether the occurred misfire is an all-cylinder misfire or a partial misfire can also be accurately identified.

A number shown at the horizontal axis of the graph of <FIG> corresponds to any one of the plurality of cylinders <NUM>, and N shown in the graph is the same value as the number of the cylinders <NUM>. In addition, the vertical axis of the graph of <FIG> indicates a sensor value which is a detection result of the cylinder sensor <NUM>.

The difference parameter acquisition unit <NUM> according to the embodiment of the present disclosure is configured to acquire a value (a value corresponding to a length L) obtained by subtracting a minimum value Amin of respective sensor values of the plurality of cylinder sensors <NUM> from an average value Aave of the plurality of sensor values as a difference parameter. With the configuration, the difference parameter indicating a difference in an operation of each of the plurality of cylinders <NUM> can be easily identified.

<FIG> is a flowchart showing an internal combustion engine misfire detecting method according to the first embodiment of the present disclosure. The present flowchart is executed by, for example, the misfire detecting device 10A (see <FIG>). When the present detecting method is started, the internal combustion engine <NUM> is driven. In the following description, steps will be abbreviated as "S" in some cases.

First, the pulsating component spectrum Sp is acquired by the pulsating component acquisition unit <NUM> described above (S11), and after then, a difference parameter is acquired by the difference parameter acquisition unit <NUM> described above (S13). Further, whether an all-cylinder misfire has occurred is determined by the all-cylinder misfire determination unit 41A described above (S15). In a case where it is determined that the all-cylinder misfire has occurred (S15: YES), the present detecting method ends. At this time, some notification processing may be executed.

In a case where it is determined that the all-cylinder misfire has not occurred (S15: NO), whether a partial misfire has occurred is determined by the partial misfire determination unit 42A described above (S17). In a case where it is determined that the partial misfire has occurred (S17: YES), the present detecting method ends. On the other hand, in a case where it is determined that the partial misfire has not occurred (S17: NO), the step returns to S11. While the internal combustion engine <NUM> operates normally without causing a misfire, S11 to S17 are repeatedly executed.

In other embodiments, S17 may not be executed. In addition, S17 may be executed before S15 is executed.

<FIG> is a conceptual diagram showing a configuration of a misfire detecting device according to the second embodiment of the present disclosure. Hereinafter, in description of the misfire detecting device 10B according to the second embodiment, identical configurations as in the misfire detecting device 10A according to the first embodiment will be assigned with identical reference signs in the drawings, and some or whole description thereof will be omitted. The misfire detecting device 10B (<NUM>) of the present example is configured to detect an all-cylinder misfire and a partial misfire, but may not detect a partial misfire.

The misfire detecting device 10B includes a change rate parameter acquisition unit <NUM> instead of the difference parameter acquisition unit <NUM> described above (see <FIG>). The change rate parameter acquisition unit <NUM> is configured to acquire a change rate parameter indicating a degree of a change in an operating parameter (change speed). The operating parameter is a parameter correlated with an overall operation status of the plurality of cylinders <NUM>. The operating parameter is, for example, an engine rotation speed, a turbo rotation speed, an inlet exhaust gas pressure of the turbine <NUM>, or the like. The operating parameter may be a parameter different from an operation parameter or may be a parameter identical to the operation parameter.

<FIG> is a graph showing changes over time in an operating parameter and a change rate parameter according to the embodiment of the present disclosure. The operating parameter given as an example in <FIG> is an engine rotation speed. In the graph of <FIG>, an all-cylinder misfire occurs at a timing of t = ta. As can be seen from the graph, when the all-cylinder misfire occurs, the operating parameter changes greatly (decreases in the example of <FIG>), and also the change rate parameter changes greatly (decreases in the example of <FIG>). Therefore, the absolute value of the change rate parameter becomes large. Although details are not shown, since some of the cylinders <NUM> operate normally when a partial misfire occurs, the operating parameter and the change rate parameter somewhat change, but do not greatly change as much as when an all-cylinder misfire occurs. In addition, in a case where all of the plurality of cylinders <NUM> operate normally, a change amount of the change rate parameter is even smaller than a time when a partial misfire occurs. The tendencies of the change rate parameters of a time when a partial misfire occurs and a time when the internal combustion engine <NUM> operates normally are the same as in a case where the operating parameter is a parameter other than the engine rotation speed.

Therefore, in a case where the pulsating component spectrum Sp has fallen below the first threshold value, when the absolute value of a change rate parameter exceeds a specific threshold value (hereinafter, referred to as the fourth threshold value), it can be determined that an all-cylinder misfire has occurred. In addition, in a case where the pulsating component spectrum Sp has fallen below the first threshold value, when the absolute value of the change rate parameter is equal to or smaller than the fifth threshold value, it can be determined that a partial misfire has occurred. The fifth threshold value is a value that is equal to or smaller than the fourth threshold value, and an embodiment in which the fifth threshold value and the fourth threshold value are values identical to each other is not excluded. Further, in a case where the pulsating component spectrum Sp has become equal to or larger than the first threshold value, when the absolute value of the change rate parameter is equal to or smaller than the fifth threshold value (or equal to or smaller than a specific value smaller than the fifth threshold value), it can be determined that the internal combustion engine <NUM> operates normally.

<FIG> is a matrix showing a relationship between a frequency spectrum, a change rate parameter, an all-cylinder misfire, and a partial misfire according to the embodiment of the present disclosure. As described above using <FIG>, when the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> is equal to or larger than the first threshold value, it can be determined that an all-cylinder misfire and a partial misfire have not occurred. In a case where the absolute value of a change rate parameter at this time is equal to or smaller than the fifth threshold value (or equal to or smaller than a specific value smaller than the fifth threshold value), it can be determined that the internal combustion engine <NUM> operates normally. On the other hand, in a case where the pulsating component spectrum Sp falls below the first threshold value, it can be determined that an all-cylinder misfire or a partial misfire has occurred. In this case, further, when the absolute value of a change rate parameter acquired by the change rate parameter acquisition unit <NUM> exceeds the fourth threshold value, it can be determined that an all-cylinder misfire has occurred, and when the absolute value of a change rate parameter is equal to or smaller than the fifth threshold value, it can be determined that a partial misfire has occurred.

Referring back to <FIG>, a misfire determination unit 40B (<NUM>) which is a component of the misfire detecting device 10B (<NUM>) includes an all-cylinder misfire determination unit 41B (<NUM>). The all-cylinder misfire determination unit 41B is configured to determine that an all-cylinder misfire has occurred in the internal combustion engine <NUM> in a case where the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> falls below the first threshold value and the absolute value of a change rate parameter acquired by the change rate parameter acquisition unit <NUM> exceeds the fourth threshold value. In an embodiment in which the change rate parameter becomes a negative value, it may be determined that whether the change rate parameter falls below a value obtained by multiplying the fourth threshold value, which is a positive value, by -<NUM>. Even with this determination method, it can be determined whether the absolute value of the change rate parameter exceeds the fourth threshold value.

With the configuration, in a case where the pulsating component spectrum Sp falls below the first threshold value and the absolute value of a change rate parameter exceeds the fourth threshold value, the all-cylinder misfire determination unit 41B determines that an all-cylinder misfire has occurred. Since whether a misfire has occurred in each of the plurality of cylinders <NUM> is not individually determined, the misfire detecting device 10B can more quickly detect occurrence of an all-cylinder misfire.

In other embodiments, in a case where the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> is equal to or larger than the first threshold value and the absolute value of a change rate parameter acquired by the change rate parameter acquisition unit <NUM> is equal to or smaller than the fifth threshold value (or equal to or smaller than a specific value smaller than the fifth threshold value), the all-cylinder misfire determination unit 41B may determine that the internal combustion engine <NUM> operates normally.

In the embodiment, the misfire determination unit 40B (<NUM>) includes a partial misfire determination unit 42B (<NUM>). The partial misfire determination unit 42B is configured to determine occurrence of a partial misfire in the internal combustion engine <NUM>. That is, the partial misfire determination unit 42B is configured to determine that a partial misfire has occurred in the internal combustion engine <NUM> in a case where the pulsating component spectrum Sp acquired by the pulsating component acquisition unit <NUM> falls below the first threshold value and the absolute value of a change rate parameter acquired by the change rate parameter acquisition unit <NUM> is equal to or smaller than the fifth threshold value.

With the configuration, the misfire detecting device 10B can identify whether a misfire which has occurred in the internal combustion engine <NUM> is a partial misfire or an all-cylinder misfire with high accuracy as the partial misfire determination unit 42B and the all-cylinder misfire determination unit 41B are included.

In some embodiments, an operating parameter is a parameter that is identical to an operation parameter. That is, the change rate parameter acquisition unit <NUM> according to the embodiment of the present disclosure is configured to acquire the operation parameter as the operating parameter. With the configuration, as the operation parameter and the operating parameter are identical to each other, a configuration for determining whether an all-cylinder misfire has occurred can be made simpler. In addition, for the same reason, a configuration for detecting whether a partial misfire has occurred can be made simpler.

An operation parameter according to the embodiment of the present disclosure is a turbine rotation speed or an inlet exhaust gas pressure of the turbine <NUM>. The turbine rotation speed or the inlet exhaust gas pressure of the turbine <NUM> quickly responses to an all-cylinder misfire that occurs in the internal combustion engine <NUM>. With the configuration, the misfire detecting device 10B of the internal combustion engine <NUM> can more quickly detect occurrence of an all-cylinder misfire. In addition, in the embodiment in which the operating parameter described above is identical to the operation parameter, the misfire detecting device <NUM> can also more quickly detect a partial misfire.

<FIG> is a flowchart showing an internal combustion engine misfire detecting method according to the second embodiment of the present disclosure. The present flowchart is executed by, for example, the misfire detecting device 10B (see <FIG>). When the present detecting method is started, the internal combustion engine <NUM> is driven.

First, the pulsating component spectrum Sp is acquired by the pulsating component acquisition unit <NUM> described above (S31), and after then, a change rate parameter is acquired by the change rate parameter acquisition unit <NUM> described above (S33). Further, whether an all-cylinder misfire has occurred is determined by the all-cylinder misfire determination unit 41B described above (S35). In a case where it is determined that the all-cylinder misfire has occurred (S35: YES), the present detecting method ends. At this time, some notification processing may be executed.

In a case where it is determined that the all-cylinder misfire has not occurred (S35: NO), whether a partial misfire has occurred is determined by the partial misfire determination unit 42B described above (S37). In a case where it is determined that the partial misfire has occurred (S37: YES), the present detecting method ends. On the other hand, in a case where it is determined that the partial misfire has not occurred (S37: NO), the step returns to S31. While the internal combustion engine <NUM> operates normally without causing a misfire, S31 to S37 are repeatedly executed.

For example, the contents described in some embodiments described above are understood as follows.

Claim 1:
An internal combustion engine misfire detecting device (<NUM>) for detecting a misfire of an internal combustion engine (<NUM>) having a plurality of cylinders (<NUM>), the internal combustion engine misfire detecting device comprising:
a pulsating component acquisition unit (<NUM>) for frequency-analyzing operation parameter data (<NUM>) indicating a change over time in an operation parameter correlated with an overall operation status of the plurality of cylinders and acquiring a pulsating component spectrum (Sp) that is a spectrum at a frequency of pulsation of the internal combustion engine;
a difference parameter acquisition unit (<NUM>) for acquiring a difference parameter correlated with a degree of a difference in an operation of each of the plurality of cylinders; and
an all-cylinder misfire determination unit (<NUM>) for determining that an all-cylinder misfire has occurred in the internal combustion engine in a case where the pulsating component spectrum acquired by the pulsating component acquisition unit falls below a first threshold value and the difference parameter acquired by the difference parameter acquisition unit falls below a second threshold value.