JP6413732B2 - Misfire diagnostic device for internal combustion engine - Google Patents

Description

  The present invention relates to a misfire diagnostic apparatus capable of diagnosing misfire of an internal combustion engine.

  When misfire of the internal combustion engine occurs, the engine output and stability are lowered, and exhaust emission is deteriorated. Therefore, conventionally, an apparatus for diagnosing misfire of the internal combustion engine has been proposed. An example of such a misfire diagnostic apparatus for an internal combustion engine is described in Patent Document 1, for example. In this device, when combustion is performed by the torque generated in the combustion stroke of the internal combustion engine, the engine speed is increased between the vicinity of the compression top dead center and the position advanced by 90 ° from the position. Since a certain amount of difference occurs, when the difference (that is, rotation fluctuation) becomes a predetermined threshold value or less, it is determined that misfire has occurred. The threshold value is set according to the moment of inertia of the power transmission system.

JP-A-10-331707

  However, if the rotation fluctuation of the internal combustion engine as a misfire parameter used for misfire diagnosis is reduced due to factors other than misfire, there is a possibility that it may be misidentified as misfire although it is not misfire. As an example of such factors, in recent years, there has been an increase in the rigidity of the damper provided on the flywheel due to the demand for drivability. , And the rotational fluctuation becomes below the threshold value for misfire diagnosis, which may cause misdiagnosis.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress misdiagnosis of misfire determination of an internal combustion engine and improve diagnosis accuracy.

Accordingly, the present invention provides a misfire parameter detection means for detecting a misfire parameter that varies according to the torque generated in the combustion stroke, and a misfire determination that determines that the internal combustion engine has misfired when the misfire parameter is equal to or less than a predetermined threshold value. in the misfire diagnostic apparatus for an internal combustion engine having a means, in all operating points of the internal combustion engine, so that the misfire parameter is not less than the threshold value, it is characterized in that the vehicle characteristic is set.

The misfire parameter is typically the minimum value of the rotation fluctuation of the internal combustion engine at the contraction point rotational fluctuation of the attenuation band to attenuate by Ri rotational fluctuation in the resonance of the vehicle rotating system at a low operating region the engine speed is contracted It is.

  According to the present invention, during operation of the internal combustion engine, the misfire parameter does not inadvertently fall below the threshold value for misfire diagnosis due to factors other than misfire. Can be improved.

The block diagram which shows the misfire diagnostic apparatus of the internal combustion engine which concerns on one Example of this invention. The characteristic view which shows the relationship between engine speed, misfire parameter MISC, and the rigidity of the damper of a flywheel. The characteristic view which shows the relationship between the rigidity of the damper of a flywheel, and the misfire parameter MISC. The characteristic view which shows the relationship between the rigidity of a drive shaft, and the misfire parameter MISC. The characteristic view which shows the relationship between the damping coefficient of a drive shaft, and the misfire parameter MISC. The characteristic view which shows the relationship between the inertia of a motor, and the misfire parameter MISC. The characteristic view which shows the relationship between the inertia of an internal combustion engine, and the misfire parameter MISC.

  Hereinafter, the present invention will be described with reference to illustrated embodiments. FIG. 1 is a block diagram showing an embodiment of a misfire diagnostic apparatus according to the present invention. The misfire diagnostic apparatus 10 includes a flywheel 13 fixed to the crankshaft 12 of the internal combustion engine 11, a magnetic pickup sensor 14, a crank angle sensor 15, and an ECM 20.

  The flywheel 13 is a dual mass type flywheel having a main flywheel 13a and a sub flywheel 13b. The main flywheel 13 a is fixed to the crankshaft 12 of the internal combustion engine 11. The sub flywheel 13b is connected to the main flywheel 13a via a spring 13c, and is not fixed to the crankshaft 12. The sub flywheel 13b and the spring 13c function as a damper that attenuates the vibration of the internal combustion engine 11. A ring gear 16 is provided around the flywheel 13.

  The magnetic pickup sensor 14 detects the rotation angle of the ring gear 16. The magnetic pickup sensor 14 outputs the detection signal to the ECM 20. The crank angle sensor 15 detects the rotation angle of the cam shaft. The crank angle sensor 15 outputs the detection signal (REF signal) to the ECM 20.

  The ECM 20 has a function of storing and executing various engine control processes, and includes a waveform shaping circuit 21, a phase detection circuit 22, a timer 23, and a misfire diagnosis unit 24. The waveform shaping circuit 21 shapes the signal waveform based on the ring gear signal of the magnetic pickup sensor 14. The phase detection circuit 22 detects the phase based on the shaped ring gear signal and the REF signal of the crank angle sensor 15.

  Based on the phase signal and the ring gear signal shaped by the waveform shaping circuit 21, the timer 23 detects a time TINT required for the internal combustion engine to rotate the specified angle. Specifically, the time TINT (rotational speed) required to rotate the specified angle near the compression top dead center where the internal combustion engine is accelerated by the combustion torque, and the advance angle, for example, 90 degrees from the vicinity of the compression top dead center. Based on the difference between the time TINT (rotational speed) required to rotate the specified angle at the specified position, the rotational fluctuation of the internal combustion engine as the misfire parameter MISC, more specifically, the attenuation region due to the resonance of the vehicle rotational system The minimum value of the rotational fluctuation of the internal combustion engine at the contraction point is obtained. The waveform shaping circuit 21, the phase detection circuit 22, and the timer 23 constitute misfire parameter detection means for detecting a misfire parameter MISC that varies according to the torque generated in the combustion stroke.

  The misfire diagnosis unit 24 determines whether or not a misfire has occurred based on the misfire parameter MISC. Specifically, when combustion has occurred, the misfire parameter MISC has a somewhat large value. If the misfire parameter MISC exceeds a predetermined threshold value Th, a misfire occurs. If it is not equal to or less than the threshold Th, it is determined that misfire has occurred. The misfire diagnosis unit 24 constitutes misfire determination means for determining misfire of the internal combustion engine.

  In this embodiment, various vehicle characteristics as shown in FIGS. 2 to 7 are set so that the misfire parameter MISC exceeds the threshold value Th at all operating points of the internal combustion engine.

  2 and 3 show the rigidity of the dampers (13b, 13c) of the flywheel 13 as the first vehicle characteristic. As shown in FIG. 2, as the damper rigidity increases, the minimum value of the rotational fluctuation at the contraction points P1 to P3 in the attenuation region due to resonance as the misfire parameter MISC decreases. Therefore, as shown in FIG. 3, the rigidity of the damper is set within a range R1 smaller than a predetermined value Q1 (a value at which the misfire parameter MISC becomes a threshold) so that the misfire parameter MISC exceeds the threshold Th. ing.

  FIG. 4 shows the rigidity of the drive shaft of the vehicle connected to the crankshaft 12 as the second vehicle characteristic. As shown in FIG. 4, the MISC increases as the rigidity of the drive shaft increases. Therefore, the rigidity of the drive shaft is set within a range R2 larger than a predetermined value Q2 (a value at which the misfire parameter MISC becomes a threshold) so that the misfire parameter MISC exceeds the threshold Th.

  FIG. 5 shows the damping coefficient of the drive shaft of the vehicle connected to the crankshaft 12 as the third vehicle characteristic. As shown in FIG. 5, the MISC increases as the damping coefficient of the drive shaft increases. Therefore, the damping coefficient of the drive shaft is set within a range R3 larger than a predetermined value Q3 (a value at which the misfire parameter MISC becomes a threshold value) so that the misfire parameter MISC exceeds the threshold value Th.

  FIG. 6 shows the inertia (moment of inertia) of the motor in the hybrid vehicle in which the internal combustion engine 11 and the motor are used together as a vehicle drive source as the fourth vehicle characteristic. As shown in FIG. 6, the misfire parameter MISC decreases as the motor inertia increases. Therefore, the inertia of the motor is set within a range R5 smaller than a predetermined value Q4 (a value at which the misfire parameter MISC becomes a threshold) so that the misfire parameter MISC exceeds the threshold Th.

  FIG. 7 shows the inertia (moment of inertia) of the internal combustion engine 11 as the fifth vehicle characteristic. As shown in FIG. 7, the misfire parameter MISC decreases as the inertia of the internal combustion engine 11 increases. Therefore, the inertia of the internal combustion engine 11 is set to be smaller than a predetermined value (a value at which the misfire parameter MISC becomes a threshold) so that the misfire parameter MISC exceeds the threshold Th.

  According to the present embodiment, the misfire parameter MISC is inadvertently determined to be misfired due to factors other than misfire at all operating points assumed during actual engine operation as operating points determined from the load and the rotational speed of the internal combustion engine. Therefore, the occurrence of misdiagnosis can be suppressed and the reliability of misfire diagnosis can be improved.

  As described above, the present invention has been described based on the specific embodiments. However, the present invention is not limited to the above-described embodiments, and includes various modifications and changes.

DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine 12 ... Crankshaft 13 ... Flywheel 13b ... Sub flywheel (damper)
13c ... Spring (damper)
20 ... ECM
21 ... Waveform shaping circuit (misfire parameter detection means)
22: Phase detection circuit (misfire parameter detection means)
23. Timer (misfire parameter detection means)
24. Misfire diagnosis (misfire determination means)

Claims (6)

Misfire parameter detection means for detecting a misfire parameter that varies in accordance with the torque generated in the combustion stroke;
In the misfire diagnostic device for an internal combustion engine, comprising: misfire determination means for determining that the misfire of the internal combustion engine when the misfire parameter is equal to or less than a predetermined threshold value,
The misfire parameter is the minimum value of the rotational fluctuation of the internal combustion engine at the contraction point where the rotational fluctuation of the attenuation region where the rotational fluctuation attenuates due to the resonance of the vehicle rotation system in the operating region where the engine rotational speed is low,
In all operating points of the internal combustion engine, so that the misfire parameter is not less than the threshold value by a factor other than misfire misfire diagnostic apparatus for an internal combustion engine, wherein a vehicle characteristic is set. The flywheel of the internal combustion engine is provided with a damper for attenuating rotational fluctuations of the internal combustion engine,
The misfire diagnostic apparatus for an internal combustion engine according to claim 1, wherein the rigidity of the damper is set to be small so that the misfire parameter exceeds the threshold value. The misfire diagnostic apparatus for an internal combustion engine according to claim 1 or 2 , wherein the rigidity of the drive shaft of the vehicle is set to be large so that the misfire parameter exceeds the threshold value. The misfire diagnostic apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein a damping coefficient of a drive shaft of a vehicle is set to be large so that the misfire parameter exceeds the threshold value. Including the internal combustion engine and a motor as a vehicle drive source;
The misfire diagnostic apparatus for an internal combustion engine according to any one of claims 1 to 4 , wherein the inertia of the motor is set small so that the misfire parameter exceeds the threshold value. As described above misfire parameter exceeds the threshold, the misfire diagnostic apparatus for an internal combustion engine according to any one of claims 1 to 5, characterized in that the inertia of the internal combustion engine is smaller.

Images