Diagnostic device and diagnostic method for internal combustion engines

Abstract

To provide a diagnostic device for an internal combustion engine that even when an existing internal combustion engine to which no cylinder pressure sensor is mounted or an internal combustion engine in which a cylinder pressure sensor has been broken is in a transient state, can estimate a combustion state of the internal combustion engine.SOLUTION: A diagnostic device for an internal combustion engine that diagnoses the internal combustion engine causing an electric motor to generate electric power includes: an electric current information acquisition section that acquires electric current information from the electric motor; a fuel injection information acquisition section that acquires fuel injection information from a control unit controlling the internal combustion engine; and a combustion abnormality detection section that estimates a combustion state of the internal combustion engine on the basis of the electric current information and the fuel injection information.SELECTED DRAWING: Figure 2

Description

[[Technical Field]]

[0001] The present invention relates to a diagnostic apparatus and a diagnostic method for an internal combustion engine that estimate the combustion state of the internal combustion engine from current information of an electric motor. [[Background Art]]

[0002] A control apparatus for an internal combustion engine that controls the internal combustion engine, for example, in an automotive internal combustion engine, in order to appropriately maintain the combustion state of the internal combustion engine, estimates the combustion state based on information from sensors attached to each part, and determines control parameters of an actuator in accordance with an accelerator opening command from an operator by a control unit. In a stationary internal combustion engine for power generation, the internal combustion engine is in communication with a power generation motor, and rotational torque generated by the internal combustion engine is converted into electric power by the power generation motor and supplied to an electric power grid. In any of these internal combustion engines, by appropriately maintaining the combustion state of the internal combustion engine, damage and abnormal vibration can be avoided. In particular, in a stationary internal combustion engine that is directly connected to an electric power grid, it is necessary to monitor the combustion state in detail and perform control to minimize variations in power supply to the electric power grid.

[0003] As a method for monitoring a combustion state, monitoring methods have generally been proposed which use a misfire sensor as a detection means when misfire occurs, a knocking sensor as a detection means when abnormal combustion occurs, and an in-cylinder pressure sensor that measures in-cylinder pressure of each cylinder of an internal combustion engine. In particular, a monitoring method using an in-cylinder pressure sensor can measure the in-cylinder pressure of each cylinder of the internal combustion engine, so that abnormal combustion can be detected. In addition, if a mechanical calculation formula for the internal combustion engine is used, the torque of the internal combustion engine can also be calculated from the in-cylinder pressure. Therefore, particularly in a stationary internal combustion engine directly connected to an electric power grid, mounting is essential for control to minimize variations in power supply to the electric power grid.

[0004] One example of a technology for suppressing abnormal combustion is Patent Document 1. The abstract of Patent Document 1 describes a solution for "effectively suppressing the occurrence of backfire in an internal combustion engine using hydrogen as fuel": "Based on the in-cylinder pressure and crank angle of each cylinder, the presence or absence of pre-ignition backfire in each cylinder is detected, and for each cylinder in which pre-ignition is detected, control is performed to increase the combustion speed, and for each cylinder in which backfire is detected, control is performed to decrease the in-cylinder temperature."

[0005] Furthermore, claim 1 of Patent Document 1 describes "a control device for an internal combustion engine in which hydrogen fuel is supplied to each cylinder from an intake path upstream of the intake valve of each cylinder, comprising: a crank angle detection means for detecting the crank angle of the internal combustion engine; an in-cylinder pressure sensor provided in each cylinder of the internal combustion engine; and an abnormal combustion detection means for detecting whether or not pre-ignition and backfire occur in each cylinder by performing abnormal combustion detection processing for each cylinder based on the in-cylinder pressure detected by each in-cylinder pressure sensor and the crank angle detected by the crank angle detection means."

[0006] One example of a technology that detects misfires using output torque is Patent Document 2. The abstract of Patent Document 2 states that, regarding misfire detection initiated when a GO signal is generated in the second cylinder of the engine, if no misfires occur in any cylinder, the current output torque command value gtrq and the previous output torque command value gtrqo do not fluctuate significantly, so it is determined that the previous cylinder, i.e., the fourth cylinder, is not misfired. On the other hand, if a misfire occurs in the fourth cylinder, gtrq drops significantly compared to gtrqo, so it is determined that there is a possibility that the fourth cylinder is misfired.

[0007] This Patent Document 2 states that, "To explain vibration damping control in more detail, the M / G·ECU17 executes the vibration damping control program shown in Figure 2 as an interrupt process each time the crankshaft 1a rotates by a predetermined small angle (for example, 0.1°). When this program starts, the M / G·ECU17 takes in the target rotational speed Ne* and the actual rotational speed Ne of the engine 1 in step (hereinafter referred to as S) 101, calculates the difference between the two rotational speeds △Ne (=Ne-Ne*) in the following S102, and calculates the output torque command value of the first M / G3 in the following S103 so that the difference △Ne becomes zero" (paragraph 0028), and that "in a hybrid vehicle performing vibration damping control, misfires in a multi-cylinder internal combustion engine can be detected with high accuracy" (paragraph 0011). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-130473 [Patent Document 2] Japanese Patent Publication No. 2000-240501 [Overview of the project] [Problems that the invention aims to solve]

[0009] Patent Document 1 describes how abnormal combustion can be detected for each cylinder by using an in-cylinder pressure sensor and a crank angle sensor.

[0010] However, the in-cylinder pressure sensor described in Patent Document 1 is very expensive, so installing it in each cylinder would result in a considerably expensive system. Moreover, if it were to be installed in an existing system, it would be necessary to disassemble the internal combustion engine, drill a hole in the engine head, and insert the in-cylinder pressure sensor. For this reason, there is a problem in that it is difficult to install the system described in Patent Document 1 in internal combustion engines that do not actually have an in-cylinder pressure sensor.

[0011] Furthermore, Patent Document 2 describes a method for detecting misfires using output torque while simultaneously performing control to suppress vibrations.

[0012] However, in transient conditions, there is a large discrepancy between the target engine speed and the actual engine speed. When using a vibration damping system to detect misfires, which is designed to suppress such vibrations, there is a problem in that false misfire detections are likely to occur.

[0013] Therefore, the present invention aims to provide a diagnostic device and method for an internal combustion engine that can estimate the combustion state of an internal combustion engine even when an existing internal combustion engine without an in-cylinder pressure sensor or an internal combustion engine with a malfunctioning in-cylinder pressure sensor is in a transient state. [Means for solving the problem]

[0014] To solve the above problems, the internal combustion engine diagnostic device of the present invention, for example, in an internal combustion engine diagnostic device that diagnoses an internal combustion engine that generates electricity using an electric motor, receives current information from the electric motor. Current value A current information acquisition unit that acquires current information, A torque component calculation unit calculates the torque component of the current value of the current information, which fluctuates according to the torque received by the electric motor from the internal combustion engine, based on the current value of the current information. Fuel injection information from the control unit that controls the internal combustion engine Fuel injection pulse width and fuel injection pressure A fuel injection information acquisition unit that acquires the following: A fuel injection amount detection unit estimates the amount of fuel injected into the internal combustion engine using the fuel injection pulse width and the fuel injection pressure, and calculates the torque peak of the torque component as a combustion characteristic from the torque component, and determines that the combustion state of the internal combustion engine is abnormal if the torque peak exceeds an upper or lower threshold value of the torque peak predetermined for each fuel injection amount. It includes a combustion abnormality detection unit.

[0015] Furthermore, the internal combustion engine diagnostic method of the present invention, for example, in a diagnostic method for an internal combustion engine that generates electricity using an electric motor, includes current information from the electric motor. Current value A current information acquisition step to obtain, A torque component calculation step, based on the current value of the current information, calculates the torque component of the current value of the current information which fluctuates in accordance with the torque received by the electric motor from the internal combustion engine, Fuel injection information from the control unit that controls the internal combustion engine Fuel injection pulse width and fuel injection pressure A step to acquire fuel injection information, A fuel injection amount detection step estimates the amount of fuel injected into the internal combustion engine using the fuel injection pulse width and the fuel injection pressure, and calculates the torque peak of the torque component as a combustion characteristic from the torque component, and determines that the combustion state of the internal combustion engine is abnormal if the torque peak exceeds an upper or lower threshold value of the torque peak predetermined for each fuel injection amount. It includes a step for detecting a combustion abnormality. [Effects of the Invention]

[0016] According to the present invention, there can be provided a diagnostic device and a diagnostic method for an internal combustion engine, which can estimate the combustion state of the internal combustion engine even when an existing internal combustion engine not equipped with an in-cylinder pressure sensor or an internal combustion engine with a failed in-cylinder pressure sensor is in a transient state. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] [Figure 1] FIG. 1 is a schematic diagram showing an outline of an engine system. [Figure 2] FIG. 2 is a functional block diagram of the diagnostic device for an internal combustion engine in Embodiment 1. [Figure 3] FIG. 3 is a diagram illustrating a method of decomposing current information into combustion intervals of each cylinder. [Figure 4] FIG. 4 is a diagram showing an example of a waveform of a torque component. [Figure 5] FIG. 5 is a diagram illustrating the relationship between fuel injection information and fuel injection amount. [Figure 6] FIG. 6 is a diagram showing an example of a fuel injection amount map in Embodiment 1. [Figure 7] FIG. 7 is a flowchart of learning processing in Embodiment 1. [Figure 8] FIG. 8 is a diagram plotting torque peaks against fuel injection amounts in Embodiment 1. [Figure 9] FIG. 9 is a flowchart of abnormality detection processing in Embodiment 1. [Figure 10] FIG. 10 is a functional block diagram of the diagnostic device for an internal combustion engine in Embodiment 2. [Figure 11] FIG. 11 is a flowchart of learning processing in Embodiment 2. [Figure 12] FIG. 12 is a diagram plotting torque peaks against fuel injection pulse width and fuel injection pressure in Embodiment 2. [Figure 13] FIG. 13 is a flowchart of abnormality detection processing in Embodiment 2. MODE FOR CARRYING OUT THE INVENTION

[0018] The diagnostic device 1 for an internal combustion engine according to an embodiment of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiment described below. In the embodiment, the internal combustion engine is described as a stationary 4-cylinder engine and the target electric motor is a synchronous motor, but the diagnostic device for an internal combustion engine of the present invention is not limited to these, and can be applied to any internal combustion engine regardless of the number of cylinders or cylinder arrangement such as inline or V-type, and regardless of the type of electric motor such as induction motor or permanent magnet motor. In addition, in each drawing used in the following description, common devices and equipment are denoted by the same reference numerals, and the descriptions of devices, equipment and operations that have already been described may be omitted. [Examples]

[0019] [Engine System] Figure 1 is a schematic diagram of an engine system. Figure 1 is a schematic diagram of an engine system that includes an internal combustion engine diagnostic device 1, an internal combustion engine 2, an electric motor 3, a power supply 4, a control unit 5, and a current information detection unit 6.

[0020] The internal combustion engine diagnostic device 1 diagnoses the combustion state of the internal combustion engine 2 based on signals from the control unit 5 and the current information detection unit 6.

[0021] The internal combustion engine 2 in this embodiment is a four-cylinder engine having four cylinders, and generates a desired combustion torque based on the control command of the control unit 5.

[0022] The electric motor 3 is a three-phase AC synchronous motor that is mechanically connected to the internal combustion engine 2. The electric motor 3 rotates at the same rotational speed as the internal combustion engine and generates regenerative power through electromagnetic induction.

[0023] Power source 4 stores the regenerative power generated by the electric motor 3. Power source 4 can be a battery or a capacitor. Power source 4 may also have the function of charging an electric vehicle by supplying the stored regenerative power. In this case, power source 4 would be used as a rapid charger. Furthermore, power source 4 may be part of the power grid of an electric company and have the function of supplying power to the power receiving equipment.

[0024] The control unit 5 outputs control commands to the internal combustion engine 2, as well as control signals to the internal combustion engine diagnostic device 1.

[0025] The current information detection unit 6 acquires current information from the motor 3. For example, a clamp-type current sensor such as a CT (Current Transformer) or Rogowski sensor can be used as the current information detection unit 6. In the case of a three-phase AC synchronous motor, the current information acquired by the current information detection unit 6 from the motor 3 must include current information for at least two phases. If the current information detection unit 6 acquires current information for two phases, the current information acquisition unit 11 will use equation (1) to obtain the current information for the third phase, as will be described later.

[0026] [Internal Combustion Engine Diagnostic Device 1] Figure 2 is a functional block diagram of the internal combustion engine diagnostic device in this embodiment. As shown in Figure 2, the internal combustion engine diagnostic device 1 includes a current information acquisition unit 11, a torque component calculation unit 12, a fuel injection information acquisition unit 13, a memory 14, a fuel injection amount detection unit 15, a combustion state learning unit 16, a combustion abnormality detection unit 17, a display unit 18, and a notification unit 19. Specifically, the internal combustion engine diagnostic device 1 is a computer equipped with hardware such as a CPU or other arithmetic unit, a main memory device such as semiconductor memory, an auxiliary storage device such as a hard disk, and a communication device. The above functions are realized by the arithmetic unit executing a program loaded into the main memory device while referring to the data recorded in the auxiliary storage device. In the following, details of each part will be explained while appropriately omitting such well-known technologies.

[0027] [Current information acquisition unit 11] The current information acquisition unit 11 acquires current information I from the current information detection unit 6. This acquisition of current information I is performed at least at sampling periods determined based on the motor's rotational speed and the current resolution. Here, it is desirable that the current information I acquired from the current information detection unit 6 includes current information for at least two phases of a three-phase (U-phase, V-phase, W-phase) AC motor. For example, if the current information acquisition unit 11 acquires current information for two phases, the U-phase and the V-phase, from the current information detection unit 6, it calculates the W-phase current information using equation (1).

[0028]

number

[0029] In equation (1), Iu, Iv, and Iw represent current information obtained from the U-phase, V-phase, and W-phase wires, respectively.

[0030] Figure 3 illustrates a method for decomposing current information into combustion sections for each cylinder. The upper part of Figure 3 shows the data extracted from the current information (current value) for one phase included in the current information acquired by the current information acquisition unit 11. In the upper part of Figure 3, the vertical axis represents the current value and the horizontal axis represents time. The current information shown is an example of a motor with 4 pole pairs, where 2 electrical cycles (720 degrees) equal a mechanical angle of 180 degrees. Therefore, in the upper part of Figure 3, the mechanical angle advances by 180 degrees in time equivalent to 2 electrical cycles.

[0031] The lower panel of Figure 3 shows the voltage history of the cam sensor attached to the engine's camshaft. In the lower panel of Figure 3, the vertical axis represents the cam sensor voltage, and the horizontal axis represents the crank angle. The cam sensor is used in engine control as a means of cylinder identification. Here, the cam sensor is exemplified as one that generates a voltage trigger once when the crank angle, which is the mechanical angle, reaches 180 degrees, and another voltage trigger immediately before the combustion section of the first cylinder in order to identify the first cylinder.

[0032] In a typical synchronous motor, slip does not occur like in an induction motor, and the rotational speed of the engine and the rotational speed of the motor are synchronized. Therefore, the rise of the cam sensor voltage shown in the upper part of Figure 3 is synchronized with the time of two electrical angle cycles in the current information shown in the lower part of Figure 3 (the dotted line in Figure 3 indicates the synchronization point). Thus, by acquiring both the cam sensor voltage and the current value, the current information can be decomposed into the combustion section of each cylinder, as shown in Figure 3.

[0033] On the other hand, by taking advantage of the characteristics of the current information of the synchronous motor, it is also possible to determine the mechanical angle from the number of pole pairs and electrical angle of the electric motor 3 without using the cam sensor signal, and to decompose the current information into combustion sections for each cylinder.

[0034] [Torque component calculation unit 12] The torque component calculation unit 12 uses the three-phase current information from the current information acquisition unit 11 to calculate the q-axis current Iq from equation (2).

[0035]

number

[0036] Here, θ in equation (2) is the electrical angle of the current information. Furthermore, the q-axis current Iq is the component of the current flowing through the motor 3 that fluctuates according to the torque received from the internal combustion engine 2. Hereafter, the q-axis current Iq will be referred to as the torque component Iq of the current.

[0037] Figure 4 shows an example of a torque component waveform. In Figure 4, the vertical axis represents the torque component -Iq of the internal combustion engine, and the horizontal axis represents the crank angle. Note that in Figure 4, for the sake of simplicity, the torque component -Iq of the internal combustion engine is shown after multiplying the torque component Iq calculated based on equation (2) by -1 to invert its sign. This is because the torque component obtained from equation (2) is the torque component detected on the electric motor 3 side, and therefore the sign is inverted for the torque component of the internal combustion engine 2. In the data shown in Figure 4, the reason why the torque component -Iq of the internal combustion engine shows a negative value is that it is before combustion in each cylinder and it is necessary to push the piston up to top dead center, and the reason why the torque component -Iq of the internal combustion engine shows a positive value is that work is done on the electric motor 3 by combustion in the cylinder. As shown in Figure 4, the torque component -Iq of the internal combustion engine has a torque peak P in the combustion section of each cylinder.

[0038] [Fuel injection information acquisition unit 13] The fuel injection information acquisition unit 13 acquires command values ​​corresponding to the fuel injection pulse width Ti and fuel injection pressure Pi output from the control unit 5 as fuel injection information. The fuel injection pulse width Ti corresponds to the valve opening time per injection of the fuel injection injector. The fuel injection pressure Pi indicates the pressure value of the fuel introduced into the fuel injection injector. Figure 5 is a diagram illustrating the relationship between fuel injection information and fuel injection amount. Specifically, Figure 5(a) shows the relationship between fuel injection pulse width Ti (horizontal axis) and fuel injection amount Q (vertical axis), and Figure 5(b) shows the relationship between fuel injection pressure Pi (horizontal axis) and fuel injection amount Q (vertical axis). As shown in Figure 5, there is a qualitatively positive correlation between the fuel injection pulse width Ti and fuel injection amount Q, and between fuel injection pressure Pi and fuel injection amount Q. The fuel injection pulse width and fuel injection pressure acquired by the fuel injection information acquisition unit 13 are examples of fuel injection information and are not limited to these. The command value of the air-fuel ratio used to determine the fuel injection amount, the intake air amount, etc., can also be used as fuel injection information.

[0039] [Fuel injection amount detection unit 15] Figure 6 shows an example of a fuel injection amount Q map. Specifically, Figure 6 is a map of fuel injection amount Q against fuel injection pulse width Ti (horizontal axis) and fuel injection pressure Pi (vertical axis). In Figure 6, darker colors indicate a higher fuel injection amount Q. It is desirable that the fuel injection amount detection unit 15 pre-records a map of fuel injection amount Q. This allows the fuel injection amount detection unit 15 to estimate the fuel injection amount Q using the fuel injection amount Q map in Figure 6 by acquiring the fuel injection pulse width Ti and fuel injection pressure Pi from the fuel injection information acquisition unit 13. Here, the units are dimensionless, but they may also be dimensioned.

[0040] [Learning Process] Figure 7 is a flowchart of the learning process in Example 1. The details of the learning process in the internal combustion engine diagnostic device 1 will be explained using the flowchart in Figure 7. This learning process may be performed at regular intervals or in response to commands from the operator.

[0041] First, in step S701, the current information acquisition unit 11 acquires current information I and proceeds to step S702. In step S702, the torque component calculation unit 12 calculates the torque component Iq from the acquired current information and proceeds to step S703. In step S703, the combustion abnormality detection unit 17 acquires the torque peak P for each combustion section of each cylinder as a combustion feature from the torque component Iq acquired in step S702. In step S704, the fuel injection information acquisition unit 13 acquires the fuel injection pulse width Ti and fuel injection pressure Pi from the control unit 5 and proceeds to step S705. In step S705, the fuel injection amount detection unit 15 estimates the fuel injection amount Q and proceeds to step S706. In step S706, the combustion state learning unit 16 learns the correlation between fuel injection amount Q and torque peak P as a combustion state estimation model MB. Based on the learned combustion state estimation model MB, it determines the upper limit threshold H and lower limit threshold L of the torque peak P. After saving the combustion state estimation model MB, the upper limit threshold H, and the lower limit threshold L to the memory 14, the learning process flow ends.

[0042] The internal combustion engine diagnostic device 1 performs learning processing in both steady-state and transient states where the rotational speed of the internal combustion engine changes little and large states where the rotational speed changes greatly, thereby enabling it to estimate the combustion state of the internal combustion engine in both steady-state and transient states and to detect abnormal combustion.

[0043] [Combustion State Learning Unit 16] Figure 8 is a plot of torque peaks against fuel injection amount in Example 1. In Figure 8, the vertical axis represents torque peak P, and the horizontal axis represents fuel injection amount Q. The combustion state learning unit 16 sequentially acquires data including pairs of torque peak P and fuel injection amount Q, and learns the correlation between torque peak P and fuel injection amount Q from the acquired data. The inventor's diligent research has shown that when the internal combustion engine 2 is operated while fluctuating rotational speed and torque, torque peak P and fuel injection amount Q show a linear correlation, although with a certain degree of variation. That is, torque peak P is related to the combustion pressure of each cylinder, and as the amount of fuel supplied to the internal combustion engine 2 increases, the combustion pressure increases, resulting in an increase in torque peak P. In other words, by learning the value of torque peak P linked to fuel injection amount conditions, it becomes possible to estimate the combustion state of the internal combustion engine 2.

[0044] Here, learning the correlation between torque peak P and fuel injection amount Q means learning the correlation function of torque peak P linked to fuel injection amount Q, for example, the distribution of torque peak P for each fuel injection amount Q as shown in Figure 8, as a combustion state estimation model MB. Furthermore, if the learned content is the distribution of torque peak P, the combustion state learning unit 16 calculates the standard deviation σ of torque peak P in the distribution of torque peak P, sets the upper threshold H of torque peak P to +3σ and the lower threshold L to -3σ, and determines the upper threshold H and lower threshold L. The combustion state learning unit 16 then stores the combustion state estimation model MB, as well as the upper threshold H and lower threshold L, in memory 14. The combustion state learning unit 16 can also integrate the information of the upper threshold H and lower threshold L with the learned distribution of torque peak P, and store the integrated distribution of torque peak P as the combustion state estimation model MB in memory 14. Furthermore, while the upper and lower thresholds H and -3σ were set to +3σ and -3σ respectively, they are not limited to these values ​​and can be changed according to the required abnormal combustion detection accuracy, etc.

[0045] The combustion state learning unit 16 learns the torque peak P for each combustion section of each cylinder shown in Figure 4. That is, it acquires the distribution of torque peak P for each combustion section and learns the correlation between torque peak P and fuel injection amount Q. In this case, a plot shown in Figure 8 is acquired for each combustion section. The combustion state learning unit 16 then determines the upper limit threshold H and the lower limit threshold L of torque peak P for each combustion section. This makes it possible to detect abnormal combustion for each cylinder. Alternatively, the combustion state learning unit 16 can learn the torque peak P for each combustion section of each cylinder shown in Figure 4 without distinguishing between them. That is, it acquires the distribution of torque peak P from the torque peak P of each combustion section and learns the correlation between torque peak P and fuel injection amount Q. In this case, the plot shown in Figure 8 will include the torque peak P of each combustion section. When learning the torque peak P without distinguishing between combustion sections, the distribution of torque peak P is acquired using the torque peak P of multiple combustion sections, so the number of data samples increases and the accuracy of the distribution improves.

[0046] [Anomaly detection processing] Figure 9 is a flowchart of the abnormality detection process in Example 1. The abnormality detection process in the internal combustion engine diagnostic device 1 will be explained using the flowchart in Figure 9. The abnormality detection process may be performed at regular intervals or in response to a command from the operator. The internal combustion engine diagnostic device 1 will perform the abnormality detection process after acquiring current information for a predetermined number of rotations of the internal combustion engine.

[0047] First, in step S801, the current information acquisition unit 11 acquires current information I and proceeds to step S802. In step S802, the torque component calculation unit 12 calculates the torque component Iq from the acquired current information and proceeds to step S803. In step S803, the combustion abnormality detection unit 17 acquires the torque peak P for each combustion section of each cylinder as a combustion feature from the torque component Iq acquired in step S802. In step S804, the fuel injection information acquisition unit 13 acquires the fuel injection pulse width Ti and fuel injection pressure Pi from the control unit 5 and proceeds to step S805. In step S805, the fuel injection amount detection unit 15 estimates the fuel injection amount Q and proceeds to step S806. In step S806, the combustion abnormality detection unit 17 refers to the upper limit threshold H and lower limit threshold L of the combustion feature quantity (torque peak P) stored in memory 14 and obtains the upper limit threshold H and lower limit threshold L of the combustion feature quantity (torque peak P) for the fuel injection quantity Q estimated by the fuel injection quantity detection unit 15. If the upper limit threshold H and lower limit threshold L for each combustion section are stored in memory 14, the combustion abnormality detection unit 17 obtains the upper limit threshold H and lower limit threshold L for the combustion section in which the torque peak P was obtained. In step S807, it is checked whether the torque peak P calculated in step S803 exceeds the upper limit threshold H or lower limit threshold L obtained in step S806. If the torque peak P exceeds the upper limit threshold H, it is determined that abnormal combustion called knocking or pre-ignition has occurred. On the other hand, if the torque peak P falls below the lower limit threshold L, it is determined that a misfire has occurred. If a threshold deviation occurs, exceeding at least one of the upper limit threshold H or lower limit threshold L, the process proceeds to step S808. In step S808, the abnormal combustion determined in S807 is displayed and reported. In this case, the display unit 18 displays the abnormal combustion, and the report unit 19 reports the abnormal combustion. If no threshold deviation occurs in step S807, the abnormality detection process is terminated. Note that the display unit 18 and the report unit 19 may also display and report the combustion state of the internal combustion engine 2 even if there is no abnormality in the combustion state of the internal combustion engine 2. If the combustion state of the internal combustion engine 2 is not abnormal, for example, a display and report of normal combustion may be considered. Furthermore, the internal combustion engine diagnostic device 1 may have only one of the display unit 18 or the report unit 19.

[0048] [Behavior during actual operation] The combustion abnormality detection unit 17 uses the combustion state estimation model MB stored in the memory 14 by the combustion state learning unit 16 to estimate the combustion state from the current information I obtained by the current information acquisition unit 11.

[0049] In this embodiment, the torque peak P of the torque component Iq was used as the combustion feature, but this is not the only option. For example, instead of the torque peak P of the torque component Iq, the RMS value of the torque component Iq can be used as the combustion feature.

[0050] As described in detail above, according to this embodiment, the combustion state estimation model MB, which estimates the combustion state from current information, makes it possible to effectively communicate abnormal combustion conditions to the operator, even if, for example, the knock sensor or in-cylinder pressure sensor of the internal combustion engine is absent or malfunctioning. [Examples]

[0051] Next, we will describe the diagnostic device 1 for an internal combustion engine according to Embodiment 2 of the present invention. Note that we will omit the explanation of the common points with Embodiment 1.

[0052] [Internal Combustion Engine Diagnostic Device 1] Figure 10 is a functional block diagram of the internal combustion engine diagnostic device 1 in Embodiment 2. As shown here, the internal combustion engine diagnostic device 1 includes a current information acquisition unit 101, a torque component calculation unit 102, a fuel injection information acquisition unit 103, a memory 104, a combustion state learning unit 105, a combustion abnormality detection unit 106, a display unit 107, and a notification unit 108. The configuration of the internal combustion engine diagnostic device 1 in Embodiment 2 is the same as the configuration of the internal combustion engine diagnostic device 1 in Embodiment 1, but with the fuel injection amount detection unit 15 omitted.

[0053] [Learning Process] Figure 11 is a flowchart of the learning process in Example 2. The details of the learning process in the internal combustion engine diagnostic device 1 will be explained using the flowchart in Figure 11. This learning process may be performed at regular intervals or in response to commands from the operator.

[0054] Steps S1101 to S1104 are the same as steps S701 to S704 in Example 1. In S1105, the combustion state learning unit 105 learns the correlation between the fuel injection pulse width Ti, the fuel injection pressure Pi, and the torque peak P as a combustion state estimation model MB. Based on the learned combustion state estimation model MB, it determines the upper limit threshold H and the lower limit threshold L of the torque peak P. After saving the combustion state estimation model MB, the upper limit threshold H, and the lower limit threshold L to the memory 104, the learning flow is terminated.

[0055] [Combustion state learning unit 105] Figure 12 is a plot of the torque peak against the fuel injection pulse width and fuel injection pressure in Example 2. In Figure 12, the torque peak P, fuel injection pulse width Ti, and fuel injection pressure Pi are the axes, respectively. The combustion state learning unit 105 sequentially acquires data including pairs of torque peak P, fuel injection pulse width Ti, and fuel injection pressure Pi, and learns the correlation between torque peak P, fuel injection pulse width Ti, and fuel injection pressure Pi from the acquired data. The inventor's diligent research has shown that when the internal combustion engine 2 is operated while varying the rotational speed and torque, the torque peak P, fuel injection pulse width Ti, and fuel injection pressure Pi show a linear correlation, although with a certain degree of variation. That is, as mentioned above, the torque peak P is proportional to the fuel injection amount Q, and this fuel injection amount Q has a positive correlation with the fuel injection pulse width Ti and fuel injection pressure Pi, respectively, as shown in Figure 5. Therefore, increasing at least one of the fuel injection pulse width Ti and fuel injection pressure Pi increases the amount of fuel supplied to the internal combustion engine 2, resulting in an increase in the torque peak P. From this, it becomes possible to estimate the combustion state of the internal combustion engine 2 by learning the torque peak P value associated with the fuel injection pulse width Ti and fuel injection pressure Pi.

[0056] Here, learning the correlation between fuel injection pulse width Ti, fuel injection pressure Pi, and torque peak P means learning the correlation function of torque peak P linked to fuel injection pulse width Ti and fuel injection pressure Pi, for example, the distribution of torque peak P for each fuel injection pulse width Ti and fuel injection pressure Pi as shown in Figure 12, as a combustion state estimation model MB. Furthermore, if the learned content is the distribution of torque peak P, the combustion state learning unit 105 calculates the standard deviation σ of torque peak P in the distribution of torque peak P, sets the upper threshold H of torque peak P to +3σ, and the lower threshold L to -3σ, and determines the upper threshold H and lower threshold L. Then, the combustion state learning unit 16 stores the combustion state estimation model MB, as well as the upper threshold H and lower threshold L, in memory 104.

[0057] The fuel injection pulse width and fuel injection pressure acquired by the fuel injection information acquisition unit 13 are examples of fuel injection information and are not limited to these. The command value of the air-fuel ratio used to determine the fuel injection amount and the intake air amount can also be used as fuel injection information. Furthermore, if the control unit 5 is calculating the command values ​​of the fuel injection amount and fuel flow rate, the fuel injection information acquisition unit 13 can also acquire the command values ​​of the fuel injection amount and fuel flow rate from the control unit 5 as fuel injection information.

[0058] [Anomaly detection processing] Figure 13 is a flowchart of the abnormality detection process in Example 2. The abnormality detection process in the internal combustion engine diagnostic device 1 will be explained using the flowchart in Figure 13. Note that the abnormality detection process may be performed at regular intervals or in response to a command from the operator.

[0059] Steps S1301 to S1304 are the same as steps S801 to S804 in Example 1. In step S1305, the combustion abnormality detection unit 106 refers to the upper limit threshold H and lower limit threshold L of the combustion feature quantity (torque peak P) stored in memory 104 and obtains the upper limit threshold H and lower limit threshold L of the combustion feature quantity (torque peak P) for the fuel injection pulse width Ti and fuel injection pressure Pi. Steps S1306 and S1307 are the same as steps S807 and S808 in Example 1.

[0060] [Behavior during actual operation] The combustion abnormality detection unit 106 uses the combustion state estimation model MB stored in the memory 104 by the combustion state learning unit 105 to estimate the combustion state from the current information I obtained by the current information acquisition unit 101.

[0061] As described in detail above, according to this embodiment, the combustion state estimation model MB, which estimates the combustion state from current information, makes it possible to effectively communicate abnormal combustion conditions to the operator, even if, for example, the knock sensor or in-cylinder pressure sensor of the internal combustion engine is absent or malfunctioning.

[0062] Furthermore, the internal combustion engine diagnostic device 1 according to this embodiment does not calculate the fuel injection amount Q from the fuel injection pulse width Ti and fuel injection pressure Pi, thus reducing the computational load. [Explanation of Symbols]

[0063] 1. Diagnostic device for internal combustion engines 11, 101 Current information acquisition section 12, 102 Torque component calculation unit 13, 103 Fuel injection information acquisition section 14,104 memory 15 Fuel injection amount detection unit 16, 105 Combustion State Learning Unit 17, 106 Combustion abnormality detection unit 18, 107 Display section 19, 108 Hochi Department 2 Internal Combustion Engine 3 Electric motor 4 Power supply 5. Control Unit 6 Current Information Detection Unit

Claims

1. In a diagnostic device for internal combustion engines that use electric motors to generate electricity, A current information acquisition unit that acquires a current value as current information from the aforementioned electric motor, A torque component calculation unit calculates the torque component of the current value of the current information, which fluctuates according to the torque received by the electric motor from the internal combustion engine, based on the current value of the current information. A fuel injection information acquisition unit that acquires fuel injection pulse width and fuel injection pressure as fuel injection information from a control unit that controls the internal combustion engine, A fuel injection amount detection unit estimates the amount of fuel injected into the internal combustion engine using the fuel injection pulse width and the fuel injection pressure, The engine includes a combustion abnormality detection unit that calculates the torque peak of the torque component as a combustion characteristic from the torque component, and determines that the combustion state of the internal combustion engine is abnormal if the torque peak exceeds an upper or lower threshold value predetermined for each fuel injection amount. A diagnostic device for internal combustion engines, characterized by the following features.

2. In the diagnostic device for an internal combustion engine according to Claim 1, The combustion abnormality detection unit determines that knocking or pre-ignition has occurred if the torque peak exceeds the upper threshold value of the torque peak predetermined for each fuel injection amount, and determines that a misfire has occurred if the torque peak falls below the lower threshold value of the torque peak predetermined for each fuel injection amount. A diagnostic device for internal combustion engines, characterized by the following features.

3. In the diagnostic device for an internal combustion engine according to claim 1, The combustion state learning unit further acquires multiple data sets including pairs of the torque peak calculated by the combustion abnormality detection unit and the fuel injection amount estimated by the fuel injection amount detection unit, calculates the standard deviation of the torque peak from the data, denotes the calculated standard deviation as σ and a predetermined value as n, and determines +nσ and -nσ as the upper and lower threshold values ​​of the torque peak for each fuel injection amount. The combustion abnormality detection unit acquires the upper limit threshold or the lower limit threshold determined by the combustion state learning unit. A diagnostic device for internal combustion engines, characterized by the following features.

4. In the diagnostic device for an internal combustion engine according to Claim 3, The above n is 3. A diagnostic device for internal combustion engines, characterized by the following features.

5. In the diagnostic device for an internal combustion engine according to claim 1, The aforementioned internal combustion engine has multiple cylinders, The current information acquisition unit decomposes the current value into combustion sections for each cylinder of the internal combustion engine, The torque component calculation unit calculates the torque component based on the current values ​​decomposed into combustion sections for each cylinder, The combustion abnormality detection unit determines abnormalities in the combustion state of each cylinder of the internal combustion engine. A diagnostic device for internal combustion engines, characterized by the following features.

6. In the diagnostic device for an internal combustion engine according to claim 1, The system further comprises at least one of the following: a display unit for displaying the combustion state of the internal combustion engine, or a notification unit for notifying the combustion state of the internal combustion engine. A diagnostic device for internal combustion engines, characterized by the following features.

7. In a diagnostic method for an internal combustion engine that uses an electric motor to generate electricity, A current information acquisition step of acquiring a current value as current information from the aforementioned electric motor, A torque component calculation step, based on the current value of the current information, calculates the torque component of the current value of the current information which fluctuates in accordance with the torque received by the electric motor from the internal combustion engine, A fuel injection information acquisition step, which acquires fuel injection pulse width and fuel injection pressure as fuel injection information from a control unit that controls the internal combustion engine, A fuel injection amount detection step in which the amount of fuel injected into the internal combustion engine is estimated using the fuel injection pulse width and the fuel injection pressure, The combustion abnormality detection step includes calculating the torque peak of the torque component as a combustion characteristic quantity from the torque component, and determining that the combustion state of the internal combustion engine is abnormal if the torque peak exceeds an upper or lower threshold value of the torque peak predetermined for each fuel injection amount. A method for diagnosing an internal combustion engine, characterized by the features described above.

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