JP2011058469A - Engine misfire detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable engine misfire detection during light load operation and prevent wrong detection in both of normal electric power generation and low electric power generation of an alternator during which no load intake pipe pressures are different. <P>SOLUTION: This engine misfire detection device detecting an engine misfire state includes an intake pipe pressure detection means detecting pressure in an engine intake pipe, and an engine misfire detection prohibition means prohibiting engine misfire detection when pressure detected by the intake pipe pressure detection means is lower than the no load intake pipe pressure. The engine misfire detection device includes an alternator electric power generation state detection means detecting an electric power generation state of the alternator by parameters relating to alternator load, and an engine misfire detection prohibition zone change over means changing over engine misfire prohibition means threshold value according to the alternator electric power generation state detected by the alternator electric power generation state detection means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting engine misfire.

  In a device that detects engine misfire, for example, in Patent Document 1, since the throttle opening is small and the fuel injection amount is small, the air-fuel ratio becomes lean and the combustion state becomes unstable, as in the case of traveling downhill. For the purpose of preventing misfire detection during load operation, when the detected pressure in the intake pipe is smaller than the pressure in the intake pipe in the no-load state, detection of misfire is prohibited.

JP-A-5-321748

  The alternator power generation voltage is controlled to improve fuel efficiency, startability during cold start, and exhaust gas reduction. However, the engine load changes depending on the power generation state of the alternator, which affects the intake pipe pressure.

  The intake pipe pressure is lower during low power generation than during normal power generation. Therefore, if the intake pipe pressure condition threshold value, which is one of the misfire detection prohibition conditions, is set in accordance with normal power generation, the intake pipe pressure will be lower than the threshold value during low power generation, and misfire detection will be prohibited. Misfire detection was not possible during low-load operation. On the other hand, if the threshold value is set in accordance with the low power generation, a diagnosis is made even in a low load region where combustion should be prohibited in the normal power generation, and misfire detection may be caused.

  An object of the present invention is to prevent false detection during low load operation both during normal power generation and during low power generation of an alternator.

  To achieve the above object, the present invention provides an intake pipe pressure detection means for detecting the pressure in the intake pipe of an engine, and a misfire when the pressure detected by the intake pipe pressure detection means is smaller than the pressure in the intake pipe in the no-load state. A misfire detection prohibiting means for prohibiting detection, an alternator power generation state detecting means for detecting the power generation state of the alternator from a parameter related to the alternator load, and a misfire detection prohibiting means according to the alternator power generation state detected by the alternator power generation state detecting means. A misfire detection prohibition region switching means for switching a threshold value is provided.

  According to the present invention, the alternator power generation state detected by the alternator power generation state detection means switches the intake pipe pressure condition set value for the misfire detection prohibition condition between normal power generation and low power generation. In both cases, misfire detection can be prevented by prohibiting misfire detection in a low load region where the combustion state is unstable.

It is a schematic block diagram of the engine misfire detection apparatus of the Example which concerns on this invention. It is a flowchart which shows misfire detection permission determination of the Example which concerns on this invention. It is a figure which shows the absolute pressure NLBST table in the intake pipe at the time of no load at the time of alternator normal power generation and low power generation.

  Examples of the present invention will be described.

  Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 is a schematic configuration diagram of an engine misfire detection apparatus according to the present embodiment.

  A throttle valve 3 is provided in the intake pipe 2 of the engine, and an electric signal corresponding to the opening degree of the throttle valve 3 is output to an engine control unit (ECU) 1 by a throttle opening degree sensor 4 connected to the throttle valve 3. .

  An intake pipe absolute pressure sensor 5 is provided in the middle of the intake pipe 2 and downstream of the throttle valve 3 to output an electrical signal corresponding to the absolute pressure to the ECU 1.

  An injector 6 is disposed for each cylinder downstream of the intake pipe absolute pressure sensor 5 and upstream of the intake valve, and the ECU 1 controls the fuel injection timing and injection time.

  A spark plug 7 is disposed for each cylinder in the cylinder head of the engine, and the ignition timing is controlled by the ECU 1.

  A water temperature sensor 9 is disposed around the cylinder block of the engine and outputs an electric signal corresponding to the engine cooling water temperature to the ECU 1.

  Unevenness of the crank plate 11 attached to the crankshaft is detected by the crank angle sensor 10 and supplied to the ECU 1 as a crank angle pulse signal.

  A cam angle sensor 8 that generates a pulse signal at a specific cam angle of the engine is installed around a cam shaft (not shown) to supply the cam angle pulse signal to the ECU 1.

  The alternator 12 arranged around the engine is controlled by the ECU 1 with the generated voltage by, for example, duty control.

  The ECU 1 measures the passage time of a specific section (rotation angular velocity detection section) of the crank plate 11 by the input crank angle pulse signal together with fuel injection control, ignition control, alternator control, etc., and detects misalignment by detecting a rotation fluctuation. Is detected.

  FIG. 2 is a misfire detection permission determination flowchart of the program of the misfire detection apparatus according to one embodiment of the present invention, and this program is executed every time the rotation angular velocity detection section of the crank angle pulse signal ends.

  In step S11, it is determined whether the engine speed NE is greater than or equal to NELWER (for example, 500 r / min) and less than or equal to NEUPER (for example, 5000 r / min). If the result is negative (NO), the process proceeds to step S19 and misfire detection is prohibited. The misfire detection permission determination process is terminated.

  On the other hand, when the result is affirmative (YES), the process proceeds to step S12.

  In step S12, it is determined whether or not the fuel injection pulse width is equal to or greater than TILW (for example, 640 μs), and it is checked whether or not the fuel injection amount can ensure stable combustion. If the determination result is negative (NO), the process proceeds to S19, where it is determined that misfire detection is prohibited, and the misfire detection permission determination process ends. On the other hand, when the determination result is affirmative (YES), the process proceeds to Step S13.

  In step S13, it is determined whether or not the engine water temperature is equal to or higher than a predetermined water temperature TWMFL (for example, 70 ° C.), and it is checked whether or not the engine water temperature can ensure stable combustion. If the determination result is negative (NO), the process proceeds to S19, where it is determined that misfire detection is prohibited, and the misfire detection permission determination process ends. On the other hand, if the determination result is affirmative (YES), the process proceeds to step S14.

  In step S14, the alternator power generation state is determined. The alternator power generation state is determined by referring to the alternator control duty. When the alternator control duty is 100%, the low power generation state is indicated, and when the alternator control duty is 0%, the normal power generation state is indicated. In step S14, it is determined whether the alternator control duty is 100%. If the determination result is affirmative (YES), the power generation state is low, and the process proceeds to step S15. When the determination result is negative (NO), the normal power generation state and alternator load fluctuation are in progress, and the process proceeds to step S16.

  In steps S15 and S16, in order to carry out misfire detection in a region where combustion is stable, it is determined whether or not the intake pipe absolute pressure detected by the intake pipe pressure detection means is higher than the intake pipe absolute pressure during no load. As shown in FIG. 3, the absolute pressure in the intake pipe at no load is NSBSTALC (for example, 3 kPa) lower during low power generation than during normal power generation of the alternator.

  Therefore, in step S15, it is determined whether or not the absolute pressure in the intake pipe is higher than the absolute pressure in the intake pipe NLBST-NSBSTALC (for example, 40 kPa during idling) at the time of low power generation when the alternator is low, and the result is negative (NO). Goes to step S19, determines that misfire detection is prohibited, and ends the misfire detection permission determination process. On the other hand, when the determination result is affirmative (YES), the process proceeds to Step S17.

  In step S16, it is determined whether or not the absolute pressure in the intake pipe is higher than the absolute pressure NLBST in the intake pipe at the time of no load during normal generator generation (for example, 43 kPa at idling). Here, even when the alternator load is fluctuating (alternator control duty is other than 100% or 0%), the alternator with a high absolute pressure in the intake pipe is used for the purpose of prohibiting misfire detection and preventing false detection. It is determined whether or not it is higher than the absolute pressure in the intake pipe. If the result is negative (NO), the process proceeds to step S19, it is determined that misfire detection is prohibited, and the misfire detection permission determination process is terminated. On the other hand, if the determination result is affirmative (YES), the process proceeds to step S17.

  In step S17, whether the amount of change in the throttle opening is greater than or equal to MFALPL (for example, −5 deg) and less than MFALPH (for example, 5 deg) for the purpose of prohibiting misfire detection and preventing false detection at the time of sudden acceleration / deceleration when the engine rotational fluctuation becomes large If the determination result is negative (NO), the process proceeds to step S19, where it is determined that misfire detection is prohibited, and the misfire detection permission determination process ends. On the other hand, when the determination result is affirmative (YES), the process proceeds to Step S18.

  In step S18, it is determined whether or not a fuel cut is in progress. If the determination result is negative (NO), the process proceeds to step S19, where it is determined that misfire detection is prohibited, and the misfire detection permission determination process ends. On the other hand, when the determination result is affirmative (YES), the process proceeds to step S20, it is determined that misfire detection is permitted, and the misfire detection permission determination process is terminated.

  In this embodiment, the alternator power generation state is determined by referring to the alternator control duty in step S14, and the threshold value of the intake pipe absolute pressure is switched. Alternatively, the alternator control ON / OFF signal, Alternatively, it is conceivable to determine the alternator power generation state based on the alternator electric energy calculation value, the alternator load torque calculation value, or the like.

1 Engine control device 2 Intake pipe 3 Throttle valve 4 Throttle opening sensor 5 Intake pipe absolute pressure sensor 6 Injector 7 Spark plug 8 Cam angle sensor 9 Water temperature sensor 10 Crank angle sensor 11 Crank plate 12 Alternator

Claims (1)

Intake pipe pressure detection means for detecting the pressure in the intake pipe of the engine;
Misfire detection prohibiting means for prohibiting misfire detection when the pressure detected by the intake pipe pressure detecting means is smaller than the no-load intake pipe pressure;
An alternator power generation state detecting means for detecting a power generation state of the alternator from a parameter related to the alternator load;
An engine misfire detection apparatus comprising: a misfire detection prohibition region switching means for switching a threshold value of the misfire detection prohibition means in accordance with an alternator power generation state detected by the alternator power generation state detection means.

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