Method and device for detecting combustion state of an internal combustion engine

Abstract

To accurately detect a combustion state of an internal combustion engine by using a detection signal of a resolver.SOLUTION: A combustion state of an internal combustion engine 1 is detected by using damper characteristics of a damper 2 connecting a front end of an electric motor rotating shaft 6 and a rear end of a crank shaft 4 and a detection signal of a resolver 7 mounted to the electric motor rotating shaft 6. The detection signal of the resolver 7 is converted into a signal that is not affected by the damper 2 by using the damper characteristics. Thus, the combustion state of the internal combustion engine 1 can be accurately detected by using the detection signal of the resolver 7 mounted to an electric motor 3.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for detecting the combustion state of an internal combustion engine. [Background technology]

[0002] For example, Patent Document 1 discloses a misfire detection device for an internal combustion engine in a so-called parallel hybrid vehicle in which an internal combustion engine, an electric motor whose rotor is coaxially connected to the crankshaft of the internal combustion engine, and a transmission are directly connected in series in that order.

[0003] In Patent Document 1, the presence or absence of a misfire in the internal combustion engine is determined based on a signal from a resolver attached to the rotor of the electric motor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-2926 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, it is not possible to grasp the combustion state (combustion situation) of the internal combustion engine using the detection signal of the resolver.

[0006] That is, there is room for further improvement in order to accurately detect (understand) the combustion state (combustion conditions) of an internal combustion engine using the detection signal of the resolver. [Means for solving the problem]

[0007] The present invention uses the damper characteristics of a damper connecting the front end of the rotating shaft of an electric motor and the rear end of the crankshaft of an internal combustion engine to perform correction on a detection signal of a resolver attached to the rotating shaft of the electric motor using a numerically modeled damper characteristic of the damper to convert the signal into a signal that is not affected by the damper, detects the combustion state of the internal combustion engine using the signal that is not affected by the damper, and when the internal combustion engine is stopped, applies torques of different values ​​to the damper from the electric motor side multiple times that are equal to or less than the friction of the internal combustion engine, thereby detecting a spring constant of the damper from the relationship between the torque generated in the electric motor and the rotation angle of the rotating shaft of the electric motor, and learns the spring constant as a spring constant in the damper characteristic of the damper, and when converting the detection signal of the resolver into a signal that is not affected by the damper , learned The damper characteristics are numerically modeled using the above spring constant. [Effects of the Invention]

[0008] According to the present invention, by correcting the resolver detection signal using the damper characteristics of the damper, the influence of the damper is removed from the resolver detection signal, and the resolver detection signal can be converted into a rotation signal at the rear end of the crankshaft with high accuracy. In other words, the resolver detection signal can be used to accurately detect the combustion state (combustion situation) of the internal combustion engine. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is an explanatory diagram showing a schematic configuration of a powertrain of a hybrid vehicle to which the present invention is applied; [Figure 2] FIG. 4 is a characteristic diagram showing a comparison between a detection signal of a crank angle sensor and a detection signal of a resolver. [Figure 3] FIG. 4 is a characteristic diagram showing a comparison of the waveforms of a detection signal from a crank angle sensor and a detection signal from a resolver corrected based on damper characteristics. [Figure 4] FIG. 4 is an explanatory diagram showing the relationship between the torque generated in the electric motor and the rotation angle of the electric motor rotary shaft when the torque is generated in the electric motor. [Figure 5]3 is a flowchart showing the flow of detection of the combustion state of an internal combustion engine and combustion control based on the detected combustion state. [Figure 6] 6 is a flowchart showing a control flow when learning the spring constant of a damper using a detection signal of a resolver. [Figure 7] 6 is a flowchart showing a control flow when learning the spring constant of a damper using a detection signal of a crank angle sensor and a detection signal of a resolver. [Figure 8] 5 is a flowchart showing a control flow when determining whether a crank angle sensor and a resolver have a malfunction. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings.

[0011] FIG. 1 is an explanatory diagram that shows a schematic configuration of a powertrain of a hybrid vehicle to which the present invention is applied.

[0012] The internal combustion engine 1 is connected to an electric motor 3 via a damper 2. The internal combustion engine 1 is, for example, a power generating internal combustion engine that drives the electric motor 3 as a generator. In other words, the torque generated by the internal combustion engine 1 is not transmitted to the drive wheels.

[0013] A crank angle sensor 5 for detecting the crank angle of the crankshaft 4 is attached to the rear end of the crankshaft 4 of the internal combustion engine 1 .

[0014] The front end of the rotating shaft (motor rotating shaft) 6 of the electric motor 3 is connected to the damper 2. A resolver 7 that detects the rotation angle of the electric motor rotating shaft 6 is attached to the rear end of the electric motor rotating shaft 6.

[0015] The detection signals of the crank angle sensor 5 and the resolver 7 are input to a control unit 8 serving as a detection section.

[0016] The control unit 8 is a well-known digital computer equipped with a CPU, ROM, RAM, and an input / output interface, and controls the internal combustion engine 1 based on detection signals from various sensors.

[0017] The control unit 8 can calculate the rotation speed of the crankshaft 4 (engine rotation speed) based on the detection signal of the crank angle sensor 5. The control unit 8 can also calculate the rotation speed of the electric motor rotating shaft 6 (electric motor rotation speed) based on the detection signal of the resolver 7.

[0018] 2 is a characteristic diagram showing a comparison between the detection signal of the crank angle sensor 5 and the detection signal of the resolver 7. The solid line in FIG. 2 represents the detection signal of the crank angle sensor 5, and the dashed line in FIG. 2 represents the detection signal of the resolver 7.

[0019] As shown in FIG. 2, the waveform of the detection signal of the resolver 7 is attenuated compared to the waveform of the detection signal of the crank angle sensor 5 due to the influence of the damper 2, and is out of phase with the waveform of the detection signal of the crank angle sensor 5 due to the influence of the electric motor rotating shaft 6.

[0020] The waveform of the detection signal of the resolver 7 can be converted into a signal that is not affected by the damper 2 by correcting it using the damper characteristics (attenuation characteristics) that are numerically modeled for the damper 2 .

[0021] 3 is a characteristic diagram showing a comparison of the waveforms of the detection signal of the crank angle sensor 5 and the detection signal of the resolver 7 corrected based on the damper characteristics of the damper 2. The solid line in FIG. 3 represents the detection signal of the crank angle sensor 5, and the dashed line in FIG. 3 represents the detection signal of the resolver 7 corrected based on the damper characteristics of the damper 2.

[0022] In addition, the phase difference between the detection signal of the crank angle sensor 5 and the waveform of the detection signal of the resolver 7 corrected based on the damper characteristics of the damper 2 can be detected by the control unit 8 based on the mechanical characteristics (material characteristics) of the electric motor rotating shaft 6.

[0023] Therefore, while the internal combustion engine 1 is operating at a predetermined constant rotation speed, the control unit 8 uses the numerically modeled damper characteristics of the damper 2 and the mechanical characteristics of the electric motor rotating shaft 6 to convert the detection signal of the resolver 7 into a signal that is not influenced by the damper 2 and the electric motor rotating shaft 6. In other words, the control unit 8 detects the combustion state of the internal combustion engine 1 using a signal obtained by correcting the detection signal of the resolver 7 using the numerically modeled damper characteristics of the damper 2 and the mechanical characteristics of the electric motor rotating shaft 6. Here, the signal that is not influenced by the damper 2 and the electric motor rotating shaft 6 is, in other words, a rotation signal at the rear end of the crankshaft.

[0024] As a result, while the internal combustion engine 1 is operating at a predetermined constant rotation speed, the control unit 8 detects (grasp) the combustion state (combustion situation) of the internal combustion engine 1 based on a signal obtained by removing the influence of the damper 2 and the electric motor rotating shaft 6 from the detection signal of the resolver 7. In other words, the combustion state of the internal combustion engine 1 can be detected with high accuracy using the detection signal of the resolver 7 attached to the rear end of the electric motor 3.

[0025] Furthermore, by detecting the combustion state of the internal combustion engine 1 using the detection signal of the resolver 7, the combustion state of the internal combustion engine 1 can be accurately grasped with a cheaper system configuration without installing an expensive in-cylinder pressure sensor for each cylinder.

[0026] The detection interval of the detection signal of the crank angle sensor 5, which detects the crank angle of the crankshaft 4 of the internal combustion engine 1, is greater than the detection interval of the detection signal of the resolver 7. The detection signal of the crank angle sensor 5 is detected, for example, every 6° of crank angle. On the other hand, the detection signal of the resolver 7 is detected, for example, every 1° of the rotational shaft angle of the resolver 7.

[0027] Therefore, the combustion state of the internal combustion engine 1 can be detected more accurately using the detection signal of the resolver 7, which has high resolution, than using the detection signal of the crank angle sensor 5.

[0028] Furthermore, by using the detection signal of the resolver 7 with high resolution, it is possible to accurately detect the combustion state of the internal combustion engine, for example, in situations such as the combustion limit in a lean burn state due to EGR, the combustion limit in lean burn, and homogeneous premixed compression ignition (HCCI) in which the pressure inside the cylinder changes significantly at a certain crank angle. This makes it possible to improve fuel efficiency and control combustion to stabilize it according to the situation even if the vehicle environment (for example, changes in outside temperature or humidity) changes significantly.

[0029] In other words, by accurately detecting the combustion state of the internal combustion engine 1, if the combustion state of the internal combustion engine 1 deviates from the target, the control unit 8 can control the ignition timing, EGR rate, air-fuel ratio, mechanical compression ratio, intake valve timing, etc. of the internal combustion engine 1 so that the combustion state of the internal combustion engine 1 becomes the target combustion state.

[0030] The damping performance of Damper 2 can be numerically modeled using the spring constant and friction resistance of Damper 2.

[0031] When the internal combustion engine 1 is stopped, the spring constant of the damper 2 can be detected and learned by causing the electric motor 3 to generate torque of different values ​​multiple times (for example, twice) that are below the friction of the internal combustion engine 1.

[0032] When the electric motor 3 generates a torque equal to or less than the friction of the internal combustion engine 1, the rotation angle of the electric motor rotary shaft 6 depends on the spring constant of the damper 2 if the internal combustion engine 1 is stopped.

[0033] Therefore, as shown in Figure 4, the spring constant of the damper 2 can be detected by linear approximation from the relationship between the torque generated in the electric motor 3 and the rotation angle of the electric motor rotating shaft 6 when the torque is generated in the electric motor 3.

[0034] 4 is an explanatory diagram showing the relationship between the torque generated in the electric motor 3 and the rotation angle of the electric motor rotating shaft 6 when the torque is generated in the electric motor 3. The rotation angle of the electric motor rotating shaft 6 can be detected using the detection signal of the resolver 7.

[0035] Points A and B in Fig. 4 indicate the torque generated in the electric motor 3 and the rotation angle of the electric motor rotating shaft 6 at that time. Characteristic line S in Fig. 4 is a straight line passing through points A and B, and its slope represents the spring constant of the damper 2.

[0036] When the internal combustion engine 1 is in operation, during a transient period when the electric motor 3 starts to operate in powered mode while the internal combustion engine 1 is running at a constant rotational speed, the spring constant of the damper 2 can be detected and learned by using the phase difference between the detection signal of the resolver 7 and the detection signal of the crank angle sensor 5 and the driving torque generated in the electric motor 3 (the amount of change in the driving torque of the electric motor 3 during the transient period).

[0037] The friction resistance of the damper 2 may be determined in advance by an experiment or the like, and stored in the ROM or the like of the control unit 8 and used.

[0038] In this way, by correcting the detection signal of the resolver 7 using the damper characteristics of the damper 2 that have been numerically modeled, the detection signal of the resolver 7 can be converted with high accuracy into a signal from which the influence of the damper 2 has been removed.

[0039] Furthermore, by detecting and learning the spring constant of the damper 2 at appropriate times, it is possible to improve the accuracy of the numerical model that represents the damper characteristics of the damper 2. In other words, by detecting the spring constant of the damper 2 at appropriate times, it is possible to grasp the damper characteristics of the damper 2 themselves at each time.

[0040] Therefore, the numerical model of the damper 2 can reflect the component variations and deterioration variations of the damper 2, thereby improving accuracy.

[0041] The timing for learning the spring constant of the damper 2 is, for example, about once per trip from when the key switch of the vehicle is turned on to when it is turned off.

[0042] Furthermore, when the internal combustion engine 1 is at a predetermined constant rotation speed and a predetermined constant load, the rotation speed of the electric motor 3 (electric motor rotating shaft 6) based on the detection signal of the resolver 7 and the rotation speed of the crankshaft 4 based on the detection signal of the crank angle sensor 5 can be compared to determine whether the resolver 7 and the crank angle sensor 5 are faulty.

[0043] For example, if the deviation between the rotation speed of the electric motor 3 (electric motor rotating shaft 6) detected by the resolver 7 and the rotation speed of the crankshaft 4 detected by the crank angle sensor 5 is within a predetermined value, it is determined that there is no malfunction in either the resolver 7 or the crank angle sensor 5.

[0044] For example, if the deviation between the rotation speed of the electric motor 3 (electric motor rotating shaft 6) based on the detection signal of the resolver 7 and the rotation speed of the crankshaft 4 based on the detection signal of the crank angle sensor 5 is greater than a predetermined value, it is determined that there is a malfunction in at least one of the resolver 7 and the crank angle sensor 5.

[0045] The resolver 7 and the crank angle sensor 5 monitor each other for abnormalities, thereby enabling failure detection for each other, thereby improving the reliability of detecting the combustion state of the internal combustion engine 1.

[0046] FIG. 5 is a flowchart showing the flow of detection of the combustion state of the internal combustion engine 1 and combustion control based on the detected combustion state.

[0047] In step S11, it is determined whether the internal combustion engine 1 is in a predetermined operating state (operating at a predetermined constant rotation speed). If the internal combustion engine 1 is in the predetermined operating state in step S11, the routine proceeds to step S12. If the internal combustion engine 1 is not in the predetermined operating state in step S11, the current routine is ended.

[0048] In step S12, the combustion state (combustion conditions) of the internal combustion engine 1 is detected using the detection signal of the resolver 7, the numerically modeled damper characteristics of the damper 2, and the mechanical characteristics of the electric motor rotating shaft 6.

[0049] In step S13, it is determined whether or not the combustion state of the internal combustion engine 1 deviates from the target. If it is determined in step S13 that the combustion state of the internal combustion engine 1 deviates from the target, the process proceeds to step S14. If it is determined in step S13 that the combustion state of the internal combustion engine 1 does not deviate from the target, the process proceeds to step S15.

[0050] In step S14, the ignition timing, mechanical compression ratio, EGR amount, intake valve timing, etc. are controlled so that the internal combustion engine 1 reaches a target combustion state.

[0051] In step S15, the internal combustion engine 1 is controlled normally.

[0052] FIG. 6 is a flowchart showing the flow of control when the spring constant of the damper 2 is detected and learned using the detection signal of the resolver 7.

[0053] In step S21, it is determined whether it is time to learn the spring constant of damper 2. If it is time to learn the spring constant of damper 2 in step S21, the process proceeds to step S22. If it is not time to learn the spring constant of damper 2 in step S21, the current routine is ended.

[0054] In step S22, it is determined whether or not the internal combustion engine 1 is stopped. If the internal combustion engine 1 is stopped in step S21, the process proceeds to step S23. If the internal combustion engine 1 is operating in step S21, the current routine is ended.

[0055] In step S23, the electric motor 3 is caused to generate torques of mutually different values ​​that are equal to or less than the friction of the internal combustion engine 1 multiple times (for example, twice).

[0056] In step S24, the spring constant of the damper 2 is detected and learned using the detection signal of the resolver 7 obtained as a result of step S23.

[0057] FIG. 7 is a flowchart showing the flow of control when the spring constant of the damper 2 is detected and learned using the detection signal of the crank angle sensor 5 and the detection signal of the resolver 7.

[0058] In step S31, it is determined whether it is time to learn the spring constant of damper 2. If it is time to learn the spring constant of damper 2 in step S31, the process proceeds to step S32. If it is not time to learn the spring constant of damper 2 in step S31, the current routine is ended.

[0059] In step S32, it is determined whether the internal combustion engine 1 is in a predetermined operating state (a transient state in which the electric motor 3 starts powering while the internal combustion engine 1 is operating at a constant rotation speed). If the internal combustion engine 1 is in the predetermined operating state in step S32, the routine proceeds to step S33. If the internal combustion engine 1 is not in the predetermined operating state in step S32, the current routine is ended.

[0060] In step S33, the spring constant of the damper 2 is detected and learned by using the phase difference between the detection signal of the resolver 7 and the detection signal of the crank angle sensor 5 and the driving torque generated in the electric motor 3 (the amount of change in the driving torque of the electric motor 3 during a transient state).

[0061] FIG. 8 is a flowchart showing the flow of control when determining whether the crank angle sensor 5 and the resolver 7 have failed.

[0062] In step S41, it is determined whether the internal combustion engine 1 is in a predetermined operating state (a predetermined constant rotation speed and a predetermined constant load). If the internal combustion engine 1 is in the predetermined operating state in step S41, the routine proceeds to step S42. If the internal combustion engine 1 is not in the predetermined operating state in step S41, the current routine is ended.

[0063] In step S42, it is determined whether the deviation between the rotation speed of the electric motor 3 (electric motor rotating shaft 6) based on the detection signal of the resolver 7 and the rotation speed of the crankshaft 4 based on the detection signal of the crank angle sensor 5 is within a predetermined value. If the deviation is within the predetermined value in step S42, the process proceeds to step S43. If the deviation is not within the predetermined value in step S42, the process proceeds to step S44.

[0064] In step S43, it is determined that neither the resolver 7 nor the crank angle sensor 5 has a malfunction.

[0065] In step S44, it is determined that at least one of the resolver 7 and the crank angle sensor 5 has a malfunction.

[0066] Although specific embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

[0067] For example, the present invention can be applied to an internal combustion engine that serves as a drive source for the drive wheels of a vehicle. In this case, when detecting (understanding) the combustion state (combustion status) of the internal combustion engine 1 using the detection signal of the resolver 7, if the drive force (rotational torque) of the internal combustion engine 1 is not being transmitted to the drive wheels, the combustion state (combustion status) of the internal combustion engine 1 can be detected (understanding) using the detection signal of the resolver 7. [Explanation of symbols]

[0068] 1...Internal combustion engine 2...Damper 3...Electric motor 4...Crankshaft 5...Crank angle sensor 6...Motor rotating shaft 7...Resolver 8...Control unit

Claims

1. A method for detecting a combustion state of an internal combustion engine, comprising: using a damper characteristic of a damper connecting a front end of a rotating shaft of an electric motor and a rear end of a crankshaft of the internal combustion engine, correcting a detection signal of a resolver attached to the rotating shaft of the electric motor by a numerically modeled damper characteristic of the damper to convert the signal into a signal that is not affected by the damper, and detecting a combustion state of the internal combustion engine using the signal that is not affected by the damper, A method for detecting the combustion state of an internal combustion engine, characterized in that when the internal combustion engine is stopped, torques of different values ​​below the friction of the internal combustion engine are applied to the damper from the electric motor side multiple times, thereby detecting the spring constant of the damper from the relationship between the torque generated in the electric motor and the rotation angle of the electric motor rotating shaft, learning the spring constant as a spring constant in the damper characteristics of the damper, and when converting the detection signal of the resolver into a signal that is not influenced by the damper, a numerically modeled damper characteristic using the learned spring constant is used.

2. 2. The combustion state detection method for an internal combustion engine according to claim 1, wherein, during a transient period when the electric motor starts powering while the internal combustion engine is operating at a constant rotational speed, a spring constant in the damper characteristics of the damper is learned using a phase difference between a detection signal of the resolver and a detection signal of a crank angle sensor that detects the rotation angle of a crankshaft of the internal combustion engine, and a driving torque of the electric motor, and the damper characteristics using the learned spring constant are utilized when converting the detection signal of the resolver into a signal that is not affected by the damper.

3. An electric motor, a damper connecting a front end of the rotary shaft of the electric motor and a rear end of the crankshaft of the internal combustion engine; a resolver attached to a rotary shaft of the electric motor; a detection unit that uses the damper characteristics of the damper to correct the detection signal of the resolver based on a numerically modeled damper characteristic of the damper to convert the signal into a signal that is not affected by the damper, and detects the combustion state of the internal combustion engine using the signal that is not affected by the damper, A combustion state detection device for an internal combustion engine, characterized in that when the internal combustion engine is stopped, torques of different values ​​below the friction of the internal combustion engine are applied to the damper multiple times from the electric motor side, and the spring constant of the damper is detected from the relationship between the torque generated in the electric motor and the rotation angle of the electric motor rotating shaft, the spring constant is learned as a spring constant in the damper characteristics of the damper, and when converting the detection signal of the resolver into a signal that is not affected by the damper, a numerically modeled damper characteristic using the learned spring constant is used.

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