Engine misfire detection device for hybrid vehicle

Abstract

The present invention improves the detection accuracy of continuous misfires of an internal combustion engine dedicated to power generation mounted on a hybrid vehicle. An engine misfire detection device is mounted on a hybrid vehicle equipped with an internal combustion engine and a generator. The internal combustion engine has a plurality of cylinders and a crankshaft and is dedicated to power generation. The generator is connected to the crankshaft via a torsional vibration damper. The engine misfire detection device includes a generator rotation angle sensor and a processor. The generator rotation angle sensor detects the rotation angle of the generator rotating shaft. The processor executes a misfire detection process for detecting misfires of the internal combustion engine. The misfire detection process includes a first misfire detection process, in which, when the amplitude correlation value detected by the generator rotation angle sensor is related to the magnitude of the rotation speed of the generator rotating shaft and is greater than a determination threshold, it is determined that a misfire has occurred in the internal combustion engine.

Description

Technical Field

[0001] The present invention relates to an engine misfire detection device for a hybrid vehicle, and more particularly to an engine misfire detection device for a hybrid vehicle having an internal combustion engine dedicated to power generation. Background Art

[0002] Patent document 1 discloses a misfire determination device for an internal combustion engine. The internal combustion engine is mounted on a hybrid vehicle with a power distribution system. Moreover, the internal combustion engine is connected to a subsequent stage (mainly a power distribution mechanism and two electric generators (MG1 and MG2)) via a torsional vibration damper. When the engine operating state does not belong to the resonance region of the subsequent stage including the damper, the misfire determination device determines the misfire through a normal misfire detection process (first method). On the other hand, when the engine operating state belongs to the resonance region of the subsequent stage including the damper, the misfire determination device determines the misfire through a resonance region misfire detection process (second method) that is different from the normal misfire detection process. Both the first and second methods are misfire detection methods based on engine rotation changes.

[0003] Patent document 2 discloses a technique for executing fuel cutoff for all cylinders for a certain period of time, and then cancelling the fuel cutoff one cylinder at a time to identify the misfiring cylinder. Patent document 3 discloses a technique for accurately and simply confirming the operation of the engine device by feedback controlling the output of the motor generator so that the rotation speed of the engine is constant when the engine is rotated with a constant shaft torque.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2011-052698

[0007] Patent Document 2: Japanese Patent Application Publication No. 2000-248989

[0008] Patent Document 3: Japanese Patent Application Publication No. 2001-268711 Summary of the invention

[0009] Problems to be solved by the present invention

[0010] However, in a series-connected hybrid vehicle (also an extended-range electric vehicle) equipped with an internal combustion engine dedicated to power generation, it is known that a torsional vibration damper is interposed between the internal combustion engine and the generator. In such a series connection, the inertia of the rotating element located on the non-engine side (i.e., the generator or motor side) relative to the torsional vibration damper becomes smaller than in a method in which the internal combustion engine is connected to the wheels together with the vehicle driving electric motor (for example, the power distribution method or parallel method described in Patent Document 1). As a result, depending on the engine rotation speed when continuous misfire occurs in a specific cylinder, it is difficult to produce engine rotation changes due to the influence of the anti-resonance point. Therefore, in an internal combustion engine dedicated to power generation mounted on a series-connected hybrid vehicle, if the previous method of utilizing engine rotation changes (rotation changes of the crankshaft) is adopted, it may be difficult to properly detect continuous misfires. Therefore, improvements in misfire detection methods are sought.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an engine misfire detection device capable of improving the detection accuracy of continuous misfires of an internal combustion engine dedicated to power generation mounted on a hybrid vehicle.

[0012] Means used to solve problems

[0013] The engine misfire detection device of a hybrid vehicle involved in the present invention is mounted on a hybrid vehicle equipped with an internal combustion engine and a generator. The internal combustion engine has a plurality of cylinders and a crankshaft, and is dedicated to power generation. The generator is connected to the crankshaft via a torsional vibration damper. The engine misfire detection device includes a generator rotation angle sensor and a processor. The generator rotation angle sensor detects the rotation angle of the generator rotating shaft. The processor executes a misfire detection process for detecting a misfire of the internal combustion engine. The misfire detection process includes a first misfire detection process, in which, when the amplitude correlation value detected by the generator rotation angle sensor is related to the magnitude of the rotation speed of the generator rotating shaft and is greater than a determination threshold, it is determined that a misfire has occurred in the internal combustion engine.

[0014] The engine misfire detection device may also include a crank angle sensor. The misfire detection process may also include a second misfire detection process, in which a misfire of the internal combustion engine is detected based on a rotational change of the crankshaft detected using the crank angle sensor. The processor may also select the first misfire detection process when a frequency value of one-half of the engine rotation frequency corresponding to the rotation speed of the crankshaft detected using the crank angle sensor is less than a specific frequency value. Furthermore, the processor may also select the second misfire detection process when the above-mentioned one-half frequency value is greater than a specific frequency value. The specific frequency value is a value of the frequency when: the ratio of the rotational angular displacement of the crankshaft to the torque of the internal combustion engine, i.e., the gain of the transfer function, is equal to the ratio of the rotational angular displacement of the generator rotating shaft to the torque of the internal combustion engine, i.e., the gain of the transfer function.

[0015] The processor may select the first misfire detection process under the engine operating condition in which the half frequency value is equal to or less than a specific frequency value and the ignition timing of the internal combustion engine is retarded from the optimum ignition timing.

[0016] The processor may execute the first misfire detection process during rapid idling of the internal combustion engine immediately after a cold start.

[0017] The amplitude-related value may be the magnitude of the full amplitude of the rotation speed of the generator rotation shaft.

[0018] Effects of the Invention

[0019] In a series hybrid vehicle (also a range-extended electric vehicle) in which the inertia of the rotating element located on the generator side relative to the torsional vibration damper is small, when continuous misfire occurs in a specific cylinder, due to the influence of the resonance of the torsional vibration damper, there is an engine rotation speed region (for example, corresponding to the later-described Fig.10 According to the first misfire detection process of the present invention, when the amplitude correlation value related to the amplitude of the rotation speed of the generator rotating shaft is greater than the determination threshold, it is determined that a misfire has occurred in the internal combustion engine. According to such a method, the detection accuracy of continuous misfires can be improved by a simple method in the use of the above-mentioned engine rotation speed range. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram showing an example of the configuration of a hybrid vehicle according to the first embodiment of the present invention.

[0021] Figure 2 : is a graph showing the relationship between the rotation variation index value and the inertia ratio R.

[0022] Figure 3Yes Figure 1 The diagram shows a modeled power transmission system P of a series hybrid vehicle.

[0023] Figure 4 is used in hybrid vehicles X and Figure 1 1 is a graph illustrating the relationship between the rotation variation index value and the frequency f while comparing series hybrid vehicles.

[0024] Figure 5 It is a time chart for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when no misfire occurs.

[0025] Figure 6 It is a time chart for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when continuous misfire occurs in a specific cylinder.

[0026] Figure 7 is a hybrid vehicle X and Figure 1 A graph showing the difference in energy ratios during consecutive misfires between series hybrid vehicles.

[0027] Figure 8 It is a time chart for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when a random misfire occurs.

[0028] Fig. 9 This is a flowchart showing the flow of the misfire detection process A according to the first embodiment.

[0029] Fig.10 This is a graph for explaining a method of selecting a misfire detection process according to the second embodiment of the present invention.

[0030] Fig.11 This is a flowchart showing the flow of the misfire detection process according to the second embodiment. DETAILED DESCRIPTION

[0031] In each embodiment described below, when the number, quantity, amount, range, etc. of each element is mentioned, the present invention is not limited to the mentioned quantity unless it is particularly clearly stated or clearly determined to be the quantity in principle.

[0032] 1. Implementation Method 1

[0033] 1-1. Composition of hybrid vehicles

[0034] Figure 1 is a schematic diagram showing an example of the configuration of the hybrid vehicle 1 according to the first embodiment. More specifically, Figure 1The figure shows a powertrain 10 provided in the hybrid vehicle 1. The powertrain 10 includes an internal combustion engine 12, a first motor generator (first MG) 14, a second motor generator (second MG) 16, a battery 18, and a control device 20.

[0035] The first MG 14 and the second MG 16 are, for example, three-phase AC type electric generators. The battery 18 stores electric power to be supplied to the first MG 14 and the second MG 16. The control device 20 controls the internal combustion engine 12, the first MG 14, and the second MG 16. The control device 20 includes an electronic control unit (ECU) 22 and a power control unit (PCU) 24. The PCU 24 is a power conversion device including an inverter for driving the first MG 14 and the second MG 16, and the PCU 24 controls the first MG 14 and the second MG 16 based on a command from the ECU 22.

[0036] The internal combustion engine 12 is, for example, a spark ignition engine. The internal combustion engine 12 has a plurality of (for example, three) cylinders 12a (first to third cylinders #1 to #3) and a crankshaft 12b. The crankshaft 12b is shared by the three cylinders 12a. The crankshaft 12b is connected to the rotating shaft 14a of the first MG 14 via a torsional vibration damper 26. In addition, the internal combustion engine 12 has an ignition device 12c (only the spark plugs arranged in each cylinder 12a are shown). The ECU 22 can change the ignition timing by controlling the ignition device 12c. Furthermore, an exhaust purification catalyst 12e is arranged in the exhaust passage 12d of the internal combustion engine 12.

[0037] The first MG 14 mainly functions as a generator. Specifically, the first MG 14 generates electricity using the power of the internal combustion engine 12. Therefore, the first MG 14 and its rotating shaft 14a are respectively equivalent to an example of the "generator" and the "generator rotating shaft" involved in the present invention. The PCU 24 converts the power generated by the first MG 14 from AC to DC and stores it in the battery 18. As a result, the battery 18 is charged. In addition, the first MG 14 functions as a motor when the engine is started. Specifically, the PCU 24 converts the power stored in the battery 18 from DC to AC power and supplies it to the first MG 14, and the first MG 14 starts the internal combustion engine 12. However, the "generator" involved in the present invention may also have only the function of a generator that uses the power of the internal combustion engine 12.

[0038] The second MG 16 is accommodated in the electric drive unit 28 together with gears such as a differential gear (not shown). The second MG 16 mainly functions as a motor for driving the hybrid vehicle 1. Specifically, the PCU 24 converts the power stored in the battery 18 from direct current to alternating current and supplies it to the second MG 16, and the second MG 16 generates torque for driving the drive shaft 30 and the wheels 32 connected to the drive shaft 30. As a result, the hybrid vehicle 1 (wheels 32) is driven.

[0039] As described above, the internal combustion engine 12 is connected to the first MG 14 but is not connected to the drive shaft 30. That is, the internal combustion engine 12 is a power generation engine and is started to generate power. In addition, not only the internal combustion engine 12 but also the first MG 14 is not connected to the drive shaft 30.

[0040] The ECU 22 has a processor 22a and a memory 22b. The memory 22b stores various data including mappings for various processes and controls of the internal combustion engine 12, the first MG 14, and the second MG 16, as well as various control programs. The processor 22a reads the control program from the memory 22b and executes it, thereby realizing various processes and controls of the control device 20. In addition, the control device 20 may also be composed of a plurality of ECUs. Specifically, for example, the control device 20 may also include an ECU for comprehensively controlling the powertrain system 10, an ECU for controlling the internal combustion engine 12, an ECU for controlling the first MG 14, and an ECU for controlling the second MG 16.

[0041] The controller 20 (ECU 22) also receives sensor signals from a sensor group for controlling the operation of the powertrain 10. The sensor group includes a crank angle sensor 34 for detecting the rotation angle (crank angle) of the crankshaft 12b and a rotary transformer (generator rotation angle sensor) 36 for detecting the rotation angle of the rotary shaft 14a of the first MG 14. The processor 22a can calculate the engine rotation speed Ne based on the signal of the crank angle sensor 34, and the processor 22a can calculate the rotation speed of the rotary shaft 14a (hereinafter referred to as "MG rotation speed Nmg") based on the signal of the rotary transformer 36.

[0042] The hybrid vehicle 1 equipped with the powertrain 10 is a so-called series hybrid vehicle. In addition, the hybrid vehicle to which the present invention is applied may also be a series plug-in hybrid vehicle in which the powertrain 10 is equipped with an external charging function. Furthermore, the vehicle to which the present invention is applied may also be a so-called range extended electric vehicle. For example, by using Figure 1The basic structure of the powertrain 10 shown is added with an external charging function and the capacity of the battery 18 is increased to form such an extended-range electric vehicle.

[0043] 1-2. Fire detection processing

[0044] Figure 1 The processor 22a included in the ECU 22 shown corresponds to an example of the "processor included in the engine misfire detection device" involved in the present invention. The processor 22a executes a misfire detection process for detecting a misfire of the internal combustion engine 12. In the present embodiment, as the misfire detection process, a "misfire detection process A" described later, which corresponds to an example of the "first misfire detection process" involved in the present invention, is executed.

[0045] The misfire patterns that occur in the internal combustion engine 12 include "continuous misfires" in which a specific cylinder misfires continuously over a plurality of cycles, and "random misfires" in which a plurality of cylinders misfire non-continuously and randomly. The misfire detection process A described below has high misfire detection performance in detecting continuous misfires of the internal combustion engine 12 dedicated to power generation mounted on the series hybrid vehicle 1. However, the misfire detection process A can also be used for detecting random misfires.

[0046] 1-2-1. Issues Related to Detection of Continuous Misfire in Series Hybrid Vehicles

[0047] In a series hybrid vehicle (hereinafter also referred to as a "series hybrid vehicle") 1, the inertia Img of the rotating element located on the non-engine side (i.e., the first MG 14 side) with respect to the torsional vibration damper 26 is smaller than that of hybrid vehicles of other modes (e.g., a power split mode or a parallel mode). The vibration mode changes due to the difference in these modes. As a result, the power transmission system P (see later described) from the internal combustion engine 12 to the first MG 14 via the torsional vibration damper 26 changes according to the engine rotation speed Ne when continuous misfire occurs. Figure 3 ) is affected by the anti-resonance point of the crankshaft 12b, and it is difficult to generate engine rotation fluctuations (i.e., rotation fluctuations of the crankshaft 12b). Therefore, in the internal combustion engine 12 dedicated to power generation mounted on the series hybrid vehicle 1, if a general method using engine rotation fluctuations is adopted, it may be difficult to appropriately detect continuous misfires. Therefore, an improvement in the misfire detection method is sought.

[0048] Next, a comparison is made between hybrid vehicle X and series hybrid vehicle 1, and the above-mentioned problem and the insights obtained therefrom are described in detail. Hybrid vehicle X is an example of a hybrid vehicle of the above-mentioned other mode, and is a power distribution mode as described in patent document 1. In addition, as an example of an engine operating condition that significantly causes the above-mentioned problem, there is a fast idling condition accompanied by a retardation angle of ignition timing (for example, the purpose of catalyst preheating). Therefore, the following detailed description of the above-mentioned problem is mainly related to the fast idling condition accompanied by such catalyst preheating. In addition, fast idling refers to the engine operation (engine preheating operation) performed while increasing the idle speed immediately after a cold start performed when the engine cooling water temperature is less than a specified value. Moreover, according to the retardation of the ignition timing performed during fast idling, for example, the ignition timing is retarded compared to the optimal ignition timing MBT (Minimum advance for the Best Torque) in order to promote the preheating of the exhaust purification catalyst 12e.

[0049] When misfire does not occur, combustion occurs once in each cylinder 12a in two rotations of the crankshaft 12b. In contrast, when continuous misfire occurs in a specific cylinder, misfire occurs at a cycle of once in two rotations of the crankshaft 12b. As a result, the periodic variation component of the engine torque Te (i.e., the torque variation component of the 0.5 frequency of the engine rotation speed Ne) caused by the continuous misfire is input to the torsional vibration damper 26. The torque variation component caused by such continuous misfire is affected by the resonance of the power transmission system P, and affects the rotation variation of the rotating shaft 14a of the first MG 14.

[0050] Figure 2 It is a graph showing the relationship between the rotation variation index value and the inertia ratio R. Figure 2 The relationship shown is determined based on the specifications of the power transmission system (internal combustion engine, torsional vibration damper, and components after the torsional vibration damper). Figure 2 The "engine side" in the figure refers to the rotating element on the engine side relative to the torsional vibration damper (i.e., mainly the crankshaft and the flywheel). In addition, the "MG side" refers to the rotating element on the non-engine side relative to the torsional vibration damper (in the hybrid vehicle X, the above-mentioned rear-stage rotating element corresponds to it, and in the series hybrid vehicle 1, the rotating shaft 14a of the first MG 14 corresponds to it).

[0051] Figure 2 The relationship under the fast idling condition (engine rotation speed Ne, for example, 1300 rpm) with catalyst warm-up is shown. Figure 2 The 20log of the vertical axis 10(MAG) represents the ratio of the rotational angular displacement (output) on the engine side / MG side to the engine torque Te (input), i.e., the gain of the transfer function, and is hereinafter referred to as the "rotational variation index value" for convenience. Figure 3 A specific example of the transfer function is described below. The rotational variation index value indicates that the larger the value is, the easier it is to generate rotational variation (in other words, the larger the amplitude of the rotational speed Ne or Nmg) due to the influence of the torsional resonance of the torsional vibration damper when receiving the input of the engine torque Te caused by continuous misfire (i.e., the input of the variation component). The large amplitude of the rotational speed Ne or Nmg is preferred in terms of high-precision misfire detection using rotational variation. Therefore, if Figure 2 As shown, the larger the rotation variation index value, the better the misfire detectability.

[0052] Figure 2 The inertia ratio R of the horizontal axis is equivalent to the ratio of the inertia Img of the rotating element on the "MG side" to the inertia Ieng of the rotating element on the "engine side". Figure 2 In the example shown, when the inertia ratio R is a predetermined value R1, the rotation variation index values ​​on the engine side and the MG side intersect. Moreover, in a low inertia ratio range lower than the predetermined value R1, the rotation variation index value on the MG side exceeds the rotation variation index value on the engine side. Therefore, it is considered that in this low inertia ratio range, by utilizing the rotation variation on the MG side, a high misfire detectability can be ensured. On the other hand, in a high inertia ratio range higher than the predetermined value R1, the rotation variation index value on the engine side exceeds the rotation variation index value on the MG side. Therefore, it can be said that in this high inertia ratio range, by utilizing the rotation variation on the engine side, a high misfire detectability can be ensured.

[0053] As shown in the above description, in the series hybrid vehicle 1, the inertia Img on the non-engine side (MG side) is small. Therefore, the inertia ratio R of the series hybrid vehicle 1 takes a value belonging to the low inertia ratio range, such as 0.26. This is not limited to the example of the series hybrid vehicle 1, but can be said to be all series hybrid vehicles. On the other hand, in the hybrid vehicle X of the power distribution method (the same is true for the parallel method), the inertia Img takes a value close to the inertia Ieng on the engine side, so its inertia ratio R takes a value belonging to the high inertia ratio range, such as 0.74.

[0054] From the above Figure 2 As can be seen from the relationship shown, under the rapid idling condition with catalyst warm-up, the detectability of continuous misfire of the internal combustion engine 12 mounted on the series hybrid vehicle 1 can be improved by utilizing the rotation fluctuation on the MG side.

[0055] Figure 3 1 is a diagram showing a power transmission system P of a series hybrid vehicle 1 in a modeled form. Figure 3 , the internal combustion engine 12 and the first MG 14, and the torsional vibration damper 26 interposed therebetween are represented by a spring element and a damping element. Figure 3 In the equation, Ieng and Img are the inertia of the rotating elements on the engine side and the MG side, respectively, and Te is the engine torque. θeng is the crank angle, and θmg is the rotation angle of the rotating shaft 14a of the first MG 14. k is the spring constant of the spring element, and c is the damping coefficient of the damping element, which takes a value of k / 1000, for example.

[0056] The motion equation of the rotating element on the engine side and the motion equation of the rotating element on the MG side can be expressed as the following equations (1) and (2), respectively. By applying Laplace transform to equations (1) and (2), equations (3) and (4) can be obtained, respectively. Equation (3) represents a transfer function showing the relationship between the rotational angular displacement Xeng (output) on the engine side and the engine torque Te (input). Equation (4) represents a transfer function showing the relationship between the rotational angular displacement Xmg (output) on the MG side and the engine torque Te (input). In Figure 2 and the following Figure 4 (A) Figure 4 (B) and Fig.10 In , the transfer function thus calculated is used.

[0057] [Formula 1]

[0058]

[0059]

[0060]

[0061]

[0062] then, Figure 4 (A) and Figure 4 (B) is a graph for explaining the relationship between the rotation variation index value and the frequency f while comparing the hybrid vehicle X and the series hybrid vehicle 1 . Figure 4 (A) and Figure 4 The relationship shown in (B) is consistent with the above Figure 2The relationship shown is the same and is determined based on the specifications of the power transmission system (internal combustion engine, torsional vibration damper, and components at the downstream stage of the torsional vibration damper). In addition, in each figure, the resonance point and anti-resonance point of the torsional vibration damper (more specifically, the power transmission system) are shown. Furthermore, the frequency value fne1 shown in each figure represents the frequency value of 0.5 times the engine rotation frequency fne corresponding to 1300 rpm (that is, the frequency value of half the engine rotation frequency fne), that is, 10.8 Hz. This 1300 rpm is an example of the value of the engine rotation speed Ne (rotation speed of the crankshaft 12b) under fast idling conditions accompanied by catalyst preheating.

[0063] Figure 4 (A) shows the frequency characteristics of the rotational variation associated with the hybrid vehicle X for comparison. In the hybrid vehicle X in which the inertia Img of the rear stage side (MG side) of the torsional vibration damper is larger than the inertia of the series hybrid vehicle 1, the engine rotation frequency value fne1 during fast idling is located at a position closer to the high frequency side than the resonance point (9.4 Hz). Moreover, at this engine rotation frequency value fne1, the rotational variation index value on the engine side exceeds the rotational variation index value on the MG side. Therefore, if it is during fast idling of the hybrid vehicle X, it can be said that it is appropriate to use the known misfire detection method using the rotational variation on the engine side.

[0064] On the other hand, in the series hybrid vehicle 1 where the inertia Img on the MG side is much smaller than the inertia of the hybrid vehicle X, as shown in FIG. Figure 4 As shown in (B), the resonance point moves to a position on the high-frequency side than the resonance point of vehicle X. As a result, the engine rotation frequency fne1 is located on the low-frequency side than the resonance point (13.4 Hz) and is close to the anti-resonance point located on the low-frequency side than the resonance point. Moreover, at the engine rotation frequency fne1, the rotation variation index value on the engine side is smaller than the rotation variation index value of the hybrid vehicle X. Therefore, it is difficult to generate rotation variation on the engine side. Therefore, it can be seen that the general misfire detection method that utilizes the engine rotation variation is inappropriate when the series hybrid vehicle 1 is idling rapidly. On the other hand, it can be seen that at the engine rotation frequency fne1, rotation variation on the MG side is easy to generate.

[0065] 1-2-2. Waveforms of engine speed and MG speed

[0066] then, Figure 5 It is a timing chart for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when no misfire occurs. Figure 61 and 2 are timing diagrams for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when continuous misfire occurs in a specific cylinder. In these diagrams, the waveforms related to the hybrid vehicle X for comparison are shown by thin solid lines, and the waveforms related to the series hybrid vehicle 1 of the present embodiment are shown by thick solid lines. In addition, in these diagrams, waveforms during fast idling accompanied by catalyst warm-up are shown, and the engine rotation speed Ne changes around a fixed value (1300 rpm as an example).

[0067] First, if Figure 5 As shown, in the case where misfire does not occur, combustion torque (engine torque Te) is generated in the order of the first cylinder #1, the second cylinder #2 and the third cylinder #3 in one cycle. The engine rotation speed Ne changes in conjunction with the change in the combustion torque. In addition, in the case where misfire does not occur, the engine rotation speed Ne in the series hybrid vehicle 1 changes in the same way as the engine rotation speed of the hybrid vehicle X. On the other hand, there is a difference in the MG rotation speed Nmg between the two. Specifically, the torque input from the engine side to the MG side is weakened due to the presence of the torsional vibration damper, but the waveform of the MG rotation speed Nmg of the series hybrid vehicle 1 with a relatively small inertia Img changes at a high frequency compared to the waveform of the hybrid vehicle X.

[0068] Then, in Figure 6 In the example shown, a continuous misfire occurs in a specific cylinder (the third cylinder #3). Figure 4 As explained above, during fast idling, rotational fluctuations on the engine side (i.e., fluctuations in the engine rotation speed Ne) are more likely to occur than rotational fluctuations on the MG side. Figure 6 As shown by the additional arrow A in FIG. 1 , the engine rotation speed Ne does not increase, and thereafter, as shown by the additional arrow B, the engine rotation speed Ne decreases significantly. This is because, in the hybrid vehicle X having a larger inertia Img than the series hybrid vehicle 1, if the combustion torque disappears due to misfire, the engine rotation speed Ne tends to decrease. As a result, as shown by the additional mark C, the amplitude of the engine rotation speed Ne accompanying the occurrence of continuous misfires becomes larger. Therefore, in the hybrid vehicle X, misfire detectability can be ensured by a general method of utilizing engine rotation variation during rapid idling accompanying catalyst warm-up.

[0069] On the other hand, in the series hybrid vehicle 1, the inertia Img on the MG side is small, so even if a misfire occurs, the engine speed Ne is unlikely to drop as shown by the additional arrow D. As a result, the amplitude of the engine speed Ne accompanying the occurrence of continuous misfires is smaller than that of the hybrid vehicle X. Figure 6It can be seen that, unlike the hybrid vehicle X which has no significant difference from the case without misfire, the MG rotation speed Nmg of the series hybrid vehicle 1 changes greatly. Figure 6 In the example of continuous misfire shown in the figure, the MG rotation speed Nmg fluctuates due to the influence of the resonance of the torsional vibration damper (more specifically, the power transmission system). Figure 6 As shown, the period of the waveform of the MG rotational speed Nmg of the series hybrid vehicle 1 having a relatively high resonance frequency (eg, 13.4 Hz) is shorter than the period of the waveform of the MG rotational speed Nmg of the hybrid vehicle X having a relatively low resonance frequency (eg, 9.4 Hz).

[0070] Next, refer to Figure 7 (A) and Figure 7 (B) provides a supplementary explanation of the analysis results of the vibration mode during continuous misfires from an energy perspective. Figure 7 (A) and Figure 7 (B) is a diagram showing the difference in energy ratio at the time of continuous misfire between the hybrid vehicle X and the series hybrid vehicle 1 . Figure 7 The energy ratios shown are calculated based on Figure 6 The torque output from the internal combustion engine 12 (ie, the engine torque Te) is converted into kinetic energy on the engine side and the MG side and strain energy of the torsional vibration damper.

[0071] Compare Figure 7 (A) and Figure 7 As can be seen from (B), the ratio of strain energy of the torsional vibration damper is the same. On the other hand, regarding kinetic energy, in the series hybrid vehicle 1, the ratio of kinetic energy on the MG side is significantly greater than that on the engine side compared to the hybrid vehicle X. This means that in the series hybrid vehicle 1, when continuous misfire occurs, rotational variation on the engine side is less likely to occur, while rotational variation on the MG side is more likely to occur.

[0072] 1-2-3. Overview of Fire Detection Process A

[0073] In view of the above problems and findings, in the present embodiment, a misfire detection process A using the rotational fluctuation on the MG side is executed to detect misfire of the internal combustion engine 12. Specifically, in the misfire detection process A, when the "amplitude correlation value" is greater than a predetermined determination threshold, the processor 22a determines that misfire has occurred in the internal combustion engine 12.

[0074] The amplitude correlation value referred to here is a value related to the amplitude of the MG rotation speed Nmg. Figure 6The full amplitude indicated by the additional mark E in the figure. In addition, the amplitude-related value may be, for example, one of the amplitudes (single amplitude (in other words, the difference between the maximum value and the average value, or the difference between the average value and the minimum value)) indicated by the additional marks F1 and F2 in the figure. Such an amplitude-related value can be calculated using the output signal of the resolver 36, for example.

[0075] In addition, the misfire detection itself is basically always performed during the operation of the internal combustion engine 12. The above description is mainly based on the rapid idling condition accompanied by catalyst warm-up, and is performed for continuous misfire. However, in the present embodiment, as an example, not only the misfire detection under the rapid idling condition, but also all the misfire detections performed during the operation of the engine are performed using the misfire detection process A.

[0076] More specifically, in the present embodiment, the misfire detection process A is executed regardless of the engine rotation speed Ne used during engine operation (in other words, regardless of the frequency value of 0.5 times the engine rotation frequency fne). In addition, the misfire pattern that can be detected by the misfire detection process A is not limited to Figure 6 As shown in FIG. 1 , the continuous misfire reflects the influence of the above-mentioned resonance with respect to the MG rotation speed Nmg. That is, the misfire detection process A can also be used, for example, to refer to the following Figure 8 Detection of random misfires is illustrated.

[0077] Figure 8 1 is a timing chart for explaining the waveforms of the engine rotation speed Ne and the MG rotation speed Nmg when a random misfire occurs. In this figure, the waveform related to the hybrid vehicle X for comparison is shown by a thin solid line, and the waveform related to the series hybrid vehicle 1 of this embodiment is shown by a thick solid line. In addition, this figure shows the waveform during fast idling accompanied by catalyst warm-up, and the engine rotation speed Ne changes around a fixed value (as an example, 1300 rpm).

[0078] In the case of random misfire, Figure 8 As shown by the arrow G marked in , the engine rotation speed Ne also decreases with the occurrence of misfire. However, in the example of random misfire in which misfire occurs alone, the MG rotation speed Nmg is not affected by the resonance of the torsional vibration damper (more specifically, the power transmission system). Therefore, as shown by the additional arrow H in the figure, after a large rotation change occurs on the MG side with the occurrence of misfire, the rotation change on the MG side immediately tends to converge. In the example of random misfire in which such a waveform of the MG rotation speed Nmg is obtained, by obtaining the amplitude-related value (for example, the size of the full amplitude) of the MG rotation speed Nmg for a specified crankshaft angle period (for example, 720°CA equivalent to one cycle), random misfire can also be detected using the misfire detection process A.

[0079] 1-2-4. Processing by the processor

[0080] Fig. 9 1 is a flowchart showing the flow of the misfire detection process A according to Embodiment 1. The process of this flowchart is repeatedly executed during the engine operation period after the start of the internal combustion engine 12 is completed.

[0081] exist Fig. 9 In step S100, the processor 22a first calculates the magnitude of the full amplitude of the MG rotation speed Nmg. More specifically, the processor 22a calculates the magnitude of the full amplitude based on the data of the MG rotation speed Nmg detected by the resolver 36 during a predetermined crank angle period (e.g., 720°CA corresponding to one cycle) required for calculating the magnitude of the full amplitude (amplitude-related value). Thereafter, the process proceeds to step S102.

[0082] In step S102, the processor 22a determines whether the total amplitude calculated in step S100 is greater than a predetermined threshold value TH1. The threshold value TH1 is predetermined to distinguish the total amplitude when various patterns of misfires including continuous misfires occur from the total amplitude when no misfire occurs.

[0083] In step S102, when the magnitude of the total amplitude is equal to or smaller than the threshold value TH1, the process proceeds to step S104. In step S104, the processor 22a determines that misfire has not occurred in the internal combustion engine 12.

[0084] On the other hand, when the magnitude of the total amplitude is larger than the threshold value TH1, the process proceeds to step S106. In step S106, the processor 22a determines that misfire has occurred in the internal combustion engine 12.

[0085] 1-3. Effect

[0086] As described above, according to the misfire detection process A for the series hybrid vehicle 1 having a small inertia Img on the MG side, by using the amplitude correlation value of the rotation variation on the MG side, the low frequency band (see FIG. 1 ) in which the rotation variation on the MG side is more likely to occur than the rotation variation on the engine side is used. Figure 4 In the case of the engine operating condition of (B)) (for example, the fast idling condition with catalyst warm-up), the detection accuracy of the continuous misfire can be improved by a simple method.

[0087] In addition, in a general misfire detection method using rotational fluctuations on the engine side, in order to improve the detection accuracy of continuous misfires, a complicated process is sometimes used to obtain the engine rotational speed Ne after excluding the torsional vibration component of the torsional vibration damper superimposed on the engine rotational speed Ne. In contrast, according to the misfire detection process A that obtains the rotational fluctuations (amplitude-related values) on the MG side using the rotation angle sensor (resolver) 36, the rotational fluctuations generated in the power transmission system P accompanying the occurrence of continuous misfires can be directly detected. Therefore, continuous misfires can be detected with high accuracy without using the complicated process described above.

[0088] In addition, in the misfire detection process A according to the present embodiment, the magnitude of the full amplitude of the MG rotation speed Nmg is used as the amplitude correlation value. Thus, a larger amplitude correlation value can be compared with the determination threshold value compared with the example of using the magnitude of the amplitude (single amplitude). Therefore, the S / N ratio related to the detection of the change of the MG rotation speed Nmg caused by the misfire can be improved, and the accuracy of the misfire detection can be improved.

[0089] In addition, if the ignition timing is delayed relative to the optimal ignition timing MBT as in the case of rapid idling with catalyst warm-up, the combustion in the cylinder 12a becomes slow. Therefore, the rotational fluctuation of the engine is less likely to occur than when the optimal ignition timing MBT is used. Therefore, in the case of continuous misfires during rapid idling with catalyst warm-up, the rotational fluctuation of the engine is not only due to the reference Figure 4 The reason described in (B) is that it is difficult to produce a continuous misfire due to the influence of the lag of the ignition timing. That is, it is significantly difficult to detect continuous misfires with high accuracy by using the general misfire detection method that utilizes the rotational variation on the engine side. In contrast, according to the misfire detection process A that does not utilize the rotational variation on the engine side, the detectability of continuous misfires under such conditions can be effectively improved. In addition, regarding the operation of reducing the lag of the ignition timing in order to improve the detectability of the rotational variation on the engine side during rapid idling accompanied by catalyst preheating, since it prolongs the time required for catalyst preheating, it will lead to an increase in the emission of exhaust emissions (unburned hydrocarbons HC). In contrast, by utilizing the misfire detection process A, such a reduction in the lag of the ignition timing will not occur, and the detectability of continuous misfires can be ensured.

[0090] 2. Implementation Method 2

[0091] The second embodiment is the same as the first embodiment described above, except that the misfire detection process is changed during the operation of the internal combustion engine 12 by a method described below.

[0092] 2-1. Fire detection processing

[0093] Fig.10This is a graph for explaining the method of selecting the misfire detection process according to the second embodiment. Fig.10 Shown with Figure 4 (B) The same relationship. Fig.10 The specific frequency value fth in is equivalent to the value of the frequency f when the rotation variation index value (gain of the transfer function) on the MG side intersects (i.e. is equal to) the rotation variation index value on the engine side. In the low frequency band B1 lower than the specific frequency value fth, the rotation variation on the MG side is easier to occur than the rotation variation on the engine side. On the other hand, in the high frequency band B2 higher than the frequency value fth, the rotation variation on the engine side is easier to occur than the rotation variation on the MG side. Therefore, in order to take into account the high misfire detectability in both the two frequency bands B1 and B2, it can be said that it is preferable to use the rotation variation on the MG side in the low frequency band B1 and the rotation variation on the engine side in the high frequency band B2.

[0094] Therefore, in the present embodiment, when the frequency value of 0.5 times the engine rotation frequency fne (that is, the frequency value of half the engine rotation frequency fne) is less than or equal to the specific frequency value fth, the above-mentioned misfire detection process A is selected. On the other hand, when the frequency value of 0.5 times is greater than the specific frequency value fth, the misfire detection process B is selected. The misfire detection process B is a process for detecting misfire of the internal combustion engine 12 based on the rotation variation of the crankshaft 12b detected by the crank angle sensor 34 (corresponding to an example of the "second misfire detection process" involved in the present invention).

[0095] 2-2. Processing by the processor

[0096] Fig.11 1 is a flowchart showing the flow of the misfire detection process according to Embodiment 2. The process of this flowchart is repeatedly executed during the engine operation period after the start of the internal combustion engine 12 is completed.

[0097] exist Fig.11 In step S200, the processor 22a first determines whether the frequency value of 0.5 times the engine rotation frequency fne (i.e., the frequency value of half the engine rotation frequency fne) is within a specific frequency value fth (refer to Fig.10 The frequency value of 0.5 is calculated using the signal of the crank angle sensor 34.

[0098] In step S200, if the frequency value of 0.5 is less than the specific frequency value fth, the process proceeds to step S202. In step S202, the processor 22a selects the misfire detection process A using the rotation variation on the MG side. Therefore, the processor 22a executes Fig. 9 Processing of the flowchart shown.

[0099] On the other hand, in step S200, when the frequency value of 0.5 is greater than the specific frequency value fth, the process proceeds to step S204. In step S204, the processor 22a selects the misfire detection process B that uses the rotation variation of the engine side detected by the crank angle sensor 34. Specifically, as the misfire detection process B, any method known in the art (for example, the method described in Patent Document 1) may be used as long as it uses the rotation variation of the engine side (variation of the engine rotation speed Ne). Therefore, a detailed description of the misfire detection process B is omitted here.

[0100] 2-3. Effect

[0101] According to the second embodiment described above, when the frequency value of the 0.5th order of the engine rotation frequency fne (i.e., the frequency value of half the engine rotation frequency fne) is less than the specific frequency value fth, the misfire detection process A using the rotation variation on the MG side is selected, and when the frequency value of the 0.5th order is greater than the specific frequency value fth, the misfire detection process B using the rotation variation on the engine side is selected. This makes it possible to take into account both the two frequency bands B1 and B2 (see Fig.10 )High fire detectability on both sides.

[0102] 3. Other Implementation Methods

[0103] (Other Examples of Engine Operating Conditions Using Misfire Detection Process A)

[0104] The misfire detection process A (first misfire detection process) using the rotational variation on the MG side can be executed not only under the fast idling condition but also when the frequency value of 0.5 times (i.e., the frequency value of half the engine rotational frequency fne) is the specific frequency value fth (refer to Fig.10 ) or other engine operating conditions below, when the ignition timing is retarded relative to the optimum ignition timing MBT for catalyst warm-up or other purposes.

[0105] In addition, under the fast idling condition of the series hybrid vehicle with a small inertia Img, the frequency value of 0.5 (the frequency value of half the above) belongs to the low frequency band B1 regardless of the specifications of the series hybrid vehicle (refer to Fig.10 The misfire detection process A may also be executed during fast idling without retardation of the ignition timing relative to the optimal ignition timing MBT for catalyst warm-up or other purposes.

[0106] (Example of Selection of Misfire Detection Processing Corresponding to Inertia Ratio R)

[0107] In the case where the rotating element on the MG side has a gear ratio, the inertia Img on the MG side is affected by the gear ratio (more specifically, the square of the gear ratio). Therefore, in a transmission system configured to be able to change the gear ratio, during the operation of the internal combustion engine 12, the inertia Img changes as the gear ratio changes, and thus the inertia ratio R (refer to Figure 2 As a result, during the operation of the internal combustion engine 12, the inertia ratio R is greater than the predetermined value R1 (refer to Figure 2 ) is low or high, which of the rotation variation on the MG side and the rotation variation on the engine side is appropriate for misfire detection may change. Therefore, in a series hybrid vehicle having a powertrain having such a configuration, the processor of the engine misfire detection device may be configured to calculate the inertia ratio R during operation of the internal combustion engine. On this basis, the processor may select the misfire detection process A (first misfire detection process) when the inertia ratio R is less than the predetermined value R1, and select the misfire detection process B (second misfire detection process) when the inertia ratio R is higher than the predetermined value R1.

[0108] Description of the label

[0109] 1 Series hybrid vehicle

[0110] 10 Powertrain

[0111] 12 Internal combustion engine

[0112] 12a Cylinder

[0113] 12b Crankshaft

[0114] 12c Ignition device

[0115] 12e Exhaust purification catalyst

[0116] 14. 1st motor generator (generator)

[0117] 14a Rotation shaft of the first motor generator (generator rotation shaft)

[0118] 16. Second motor generator (motor)

[0119] 18 Batteries

[0120] 20 Control device

[0121] 22 Electronic Control Unit (ECU)

[0122] 22a processor

[0123] 26 Torsional vibration damper

[0124] 32 Wheels

[0125] 34 Crank angle sensor

[0126] 36 Resolver (generator rotation angle sensor).

Claims

1. An engine misfire detection device for a hybrid vehicle, the engine misfire detection device being mounted on a hybrid vehicle having an internal combustion engine and a generator dedicated to power generation, the internal combustion engine having a plurality of cylinders and a crankshaft, the generator having a generator rotating shaft connected to the crankshaft via a torsional vibration damper, the engine misfire detection device being characterized in that: The engine misfire detection device comprises: a generator rotation angle sensor that detects a rotation angle of a rotation shaft of the generator; and a processor that performs a misfire detection process for detecting a misfire of the internal combustion engine, The misfire detection process includes a first misfire detection process, in which, when an amplitude-related value of the rotation speed of the generator rotating shaft detected by the generator rotation angle sensor is greater than a determination threshold, it is determined that a misfire has occurred in the internal combustion engine, wherein the amplitude-related value is the size of a full amplitude or a single amplitude of the rotation speed of the generator rotating shaft.

2. The engine misfire detection device for a hybrid vehicle according to claim 1, characterized in that: The engine misfire detection device further comprises a crank angle sensor, The misfire detection process includes a second misfire detection process in which a misfire of the internal combustion engine is detected based on a rotational variation of the crankshaft detected by the crank angle sensor. the processor selects the first misfire detection process when a frequency value of one-half of the engine rotation frequency corresponding to the rotation speed of the crankshaft detected by the crank angle sensor is less than a specific frequency value, and selects the second misfire detection process when the one-half frequency value is greater than the specific frequency value, The specific frequency value is the frequency value when the ratio of the rotational angular displacement of the crankshaft to the torque of the internal combustion engine, i.e., the gain of the transfer function, is equal to the ratio of the rotational angular displacement of the generator rotating shaft to the torque of the internal combustion engine, i.e., the gain of the transfer function.

3. The engine misfire detection device for a hybrid vehicle according to claim 2, characterized in that: The processor selects the first misfire detection process under the engine operating condition in which the half frequency value is equal to or less than the specific frequency value and the ignition timing of the internal combustion engine is retarded from the optimum ignition timing.

4. The engine misfire detection device for a hybrid vehicle according to any one of claims 1 to 3, characterized in that: The processor executes the first misfire detection process during rapid idling of the internal combustion engine immediately after a cold start.

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