JP2008138523A - Engine combustion state diagnosis device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately detect abnormal combustion (misfire), and to satisfy legal requirements even in a fast idle ignition retard control region for reducing emission immediately after cold starting. <P>SOLUTION: The engine combustion state diagnosis device is provided with a means for measuring elapsed time that a crankshaft rotates a predetermined angle and calculating a combustion state parameter from its time signal, a means for comparing the combustion state parameter with an abnormal combustion determination value and detecting abnormal combustion (misfire), and a means for correcting the abnormal combustion determination value by a coefficient calculated from an ignition retard amount. The misfire can be accurately detected even in the fast idle ignition retard region just after cold starting. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a combustion state detection device for an engine, and more particularly to a combustion state diagnosis device that enables accurate detection of abnormal combustion (misfire) even during fast idle ignition retard control that operates immediately after cold start.

  2. Description of the Related Art Conventionally, a technique for detecting a combustion state by measuring the number of revolutions using the relationship between torque generated by engine combustion and the number of revolutions and indirectly detecting abnormal combustion (misfire) is known. (See, for example, Patent Document 1 below). This technique detects the rotational speed of the engine in at least two ignitions in one ignition cycle from the previous ignition to the current ignition, and the engine rotational speed fluctuations in the one ignition cycle are detected based on the difference in the rotational speeds. By calculating the value, calculating the rotational speed fluctuation value obtained sequentially, detecting the combustion state of the engine using the result of the calculation process, and comparing it with a specific judgment value, The detection is performed.

JP 58-51243 A (pages 1-8, FIGS. 1-8)

  In recent years, due to stricter emission regulations aimed at protecting the environment, there is a system that employs fast idle ignition retard control that lowers the emission temperature by retarding the ignition timing in the idle state after cold start and reduces emissions It is increasing.

  In addition, since engine torque decreases during ignition retard, if misfire occurs under this low torque condition, torque fluctuation due to misfire is small, and as a result, the level of the combustion state parameter at the time of misfire is lower than the misfire in the normal region. A phenomenon of lowering occurs.

  In other words, in the conventional misfire diagnosis in which misfire detection is performed using the relationship between the torque generated by engine combustion and the rotational speed, if a misfire occurs under the condition that the ignition retard is activated, the combustion state parameter is abnormal. There is a problem that the combustion judgment value cannot be exceeded and misfire detection cannot be performed.

  On the other hand, in North America in recent years, the occurrence of misfire before catalyst activation, such as after cold start, has a great influence on air pollution. Therefore, it is necessary to construct a logic that can reliably detect misfire even within the first 1000 revolutions after starting.

  The present invention has been made to solve the conventional problems as described above. The purpose of the present invention is to accurately detect abnormal combustion (misfire) even in a region where ignition retard control for reducing emissions is performed immediately after the start of cold engine. It is an object of the present invention to provide an engine combustion state diagnosing device capable of detecting the above.

  An engine combustion state diagnosis apparatus according to the present invention includes a crank angle sensor for detecting a crank angle, measures an elapsed time during which the crankshaft rotates a predetermined angle, and determines a combustion state from the time signal. A means for calculating a parameter, a means for comparing the combustion state parameter with an abnormal combustion determination value and detecting abnormal combustion (misfire) of the engine, and the abnormal combustion determination value is expressed by MBT (MBT: Minimum advance for the Best Torqu), That is, it is achieved by a configuration comprising: a means for correcting when the combustion state parameter decreases with a decrease from the torque at the ignition timing at which the output and the fuel consumption rate are the best.

  More preferably, the coefficient for correcting the abnormal combustion determination value is achieved as a function of the retard amount from the MBT ignition timing.

  More preferably, the coefficient for correcting the abnormal combustion determination value is achieved as a function of the ignition timing.

  More preferably, the abnormal combustion determination value search map is achieved by selecting the ignition retard amount.

  More preferably, the abnormal combustion determination value search map is achieved by selecting whether or not the ignition retard is present.

  More preferably, one of the abnormal combustion determination value maps is achieved by using a function of the ignition retard amount and the engine speed or the engine load.

  More preferably, one of the abnormal combustion determination value maps is achieved by using a function of ignition timing and engine speed or engine load.

  More preferably, the means for correcting the abnormal combustion determination value by a coefficient corresponding to the ignition retard amount or the ignition timing and the means for selecting the determination value search map are equal to or less than a specific engine speed or a specific engine speed. This is achieved by making the number more than.

  More preferably, the means for correcting the abnormal combustion determination value with a coefficient corresponding to the ignition retard amount or the ignition timing and the means for selecting the abnormal combustion determination value map are the off-idle determination, time, or number of ignitions. Achieved by discontinuing

  In the combustion state diagnosis apparatus according to the present invention, even in the region where ignition retard is entered immediately after the start of cold engine, the abnormal combustion determination value is corrected according to the ignition retard amount or the ignition timing, so that abnormal combustion (misfire) is accurately detected. it can.

  The countermeasure for the misfire detection leakage that occurs at the time of ignition retard operation immediately after the cold start is realized by the construction of the control logic.

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

  FIG. 1 is a schematic configuration diagram showing an embodiment of a combustion state diagnosis apparatus according to the present invention together with an in-vehicle engine to which it is applied.

  In FIG. 1, the engine 10 is provided with an ignition device 201 in its combustion chamber 214, and the flow rate of air taken in from an air cleaner 200 provided at the tip of the intake passage 220 is adjusted by a throttle valve 213. Thereafter, the flow rate passing through the air flow sensor 204 is measured and mixed with the fuel injected from the fuel injection valve 202 at a predetermined angle to burn each cylinder (# 1, # 2, # 3, # 4). Supplied to the chamber 214. The exhaust passage 230 is provided with an air-fuel ratio sensor 205, a three-way catalyst 206, and the like. The exhaust gas is purified by the three-way catalyst 206 and then discharged to the atmosphere.

  On the other hand, after the fuel in the fuel tank 209 is sucked and pressurized by the fuel pump 210, it is guided to the fuel inlet of the fuel injection valve 202 through the fuel piping system 212 provided with the pressure regulator 211, and excess fuel. Is returned to the fuel tank 209. In the present embodiment, an in-line four-cylinder engine will be described as an example, but the present invention is not limited to this.

  In addition to the above-described configuration, a control unit 207 having a well-known configuration is provided to control the ignition timing by the ignition device 201, the fuel injection amount (air-fuel ratio) by the fuel injection valve 202, and the like. Yes. The control unit 207 has a signal corresponding to the intake air amount (Qa) detected by the air flow sensor 204, the rotation speed of the crank angle plate 208 attached to the crankshaft detected by the rotation angle sensor 203 (engine speed ( Ne)), a signal corresponding to the air-fuel ratio detected by the air-fuel ratio sensor 205, and the like are supplied. Based on these signals, the control unit 207 controls ignition timing, fuel injection (air-fuel ratio) control, etc. And a diagnosis of the combustion state (determination of the presence or absence of abnormal combustion such as misfire).

  FIG. 2 is a functional block diagram showing the combustion state diagnosis contents executed by the control unit 207, and means 101 for measuring the time required for the crank angle plate 208 attached to the crankshaft to rotate a predetermined angle; Means 102 for calculating a pitch error correction amount, combustion state parameter calculation means 103 for calculating a combustion state parameter from the required time and the pitch error correction amount, and an abnormality for calculating an abnormal combustion determination value from the engine speed and engine load Combustion determination value calculation means 104, determination value correction coefficient calculation means 105 for calculating a coefficient for correcting the abnormal combustion determination value according to the ignition retard amount or ignition timing, and the final value from the abnormal combustion determination value and the determination value correction coefficient A final abnormal combustion determination value calculation means 106 for calculating an abnormal combustion determination value; and the combustion state parameter Based on over data and final abnormal combustion determination value includes the abnormal combustion determination means 107 to determine the presence or absence of abnormal combustion such as misfire, the.

  Here, the combustion state diagnosis of the present embodiment will be described from the premise facts and considerations based on the facts.

FIG. 3 is a graph showing changes in the rotational speed with respect to the crank angle of the engine. This is the waveform when misfire occurs in the third cylinder # 3, and the broken line is when the combustion state is normal. In FIG. 3, the rotation speed measurement section [hereinafter referred to as window width (predetermined crank angle)] for each cylinder (# 1, # 2, # 3, # 4) will be described.

  Based on the reference signal REF, the TDC (piston top dead center) of each cylinder is detected. The first crank angle is obtained from the TDC using the angle signal POS and is set as the window start point Ws. The second crank angle is obtained from the window start point Ws using the same angle signal POS, and the window width W is defined from the first crank angle to the second crank angle.

  The window passing time of the cylinder in the ignition cycle is now Tw (i), and the combustion state parameter D1A1 is obtained from the following equation 1.

<Formula 1>
D1A1 = {Tw (i) −Tw (i−1)} / Tw ³ (i) × k
However,
Tw (i): Window W passage time of the cylinder currently in the ignition cycle Tw (i-1): Window W passage time of the cylinder in the previous ignition cycle k: Calculation coefficient D1A1: Combustion state parameter FIG. The behavior of the combustion state parameter D1A1 calculated | required by the window passage time Tw (i) at the time of misfire and Formula (1) is shown.

  When the combustion state of the engine is normal, the window passing time of each cylinder is almost equal, and thus the combustion state parameter D1A1 is almost zero. However, when the engine is misfired, torque is not generated in the misfire cylinder and the rotational speed is reduced. As shown in FIG. 4A, the value of Tw (i) increases. At this time, the combustion state parameter D1A1 shows a certain positive value as shown in FIG. Therefore, the presence or absence of a misfire cylinder can be detected by comparing the combustion state parameter D1A1 with a preset value.

  Specifically, as shown in FIG. 5, the combustion state parameter D1A1 is compared with a preset final abnormal combustion determination value D1ATH, and when D1A1 ≧ D1ATH, it is determined that a misfire has occurred and the misfire counter CMTLB is counted up. When D1A1 <D1ATH, the misfire count is not increased as a normal combustion state. When the count number of the misfire counter CMTLB exceeds a preset value (MIL lighting threshold value), the MIL (warning lamp) on the meter panel is turned on to warn the driver.

  FIG. 6 is an example in which misfire is forcibly generated in the state where the idle ignition retard immediately after the start of the cold engine is activated, and the misfire detection property at that time is confirmed.

As can be seen from the figure, misfire is detected immediately after starting, but as the idle ignition retard is entered, the level of the combustion state parameter D1A1 becomes smaller and the final abnormal combustion determination value D1ATH cannot be exceeded, and misfire detection is leaked. Has occurred.

  As a result, the integrated value of the misfire count number CMTLB cannot reach the MIL (warning lamp) lighting threshold value, and the misfire determination cannot be made within 1000 revolutions of the start. In addition, this case cannot satisfy the regulations.

  As one of the measures for solving the misfire detection leakage at the time of operating the first idle ignition retard, a means for correcting the first idle ignition retard or the abnormal combustion determination value according to the ignition timing is proposed.

  FIG. 7 shows one of the correction methods. In addition to the conventional abnormal combustion determination value map, FIG. 7 has a correction coefficient corresponding to the ignition retard amount and calculates a final abnormal combustion determination value. .

  A specific formula is shown below.

<Formula 2>
D1ATH = MDTH1 × KFIR
Here, KFIR = TKFIR.
MDTH1: Abnormal combustion determination value map search value KFIR: Correction coefficient at ignition retard TKFIR: Correction coefficient table search value at ignition retard D1ATH: Final abnormal combustion determination value Here, the correction coefficient is a required value depending on the ignition retard amount as shown in FIG. Are different from each other, and are used as a function of the ignition retard amount.

  FIG. 9 shows a specific behavior of the final abnormal combustion judgment value D1ATH. When there is no ignition retard, the correction coefficient is 1.0. However, as the ignition retard is entered, the correction coefficient becomes smaller and the final abnormal combustion occurs. The determination value D1ATH decreases.

  Thus, the combustion state parameter D1A1 can exceed the final abnormal combustion determination value D1ATH, and misfire can be detected even during the ignition retard operation.

  FIG. 10 shows an example of means for using the correction coefficient as a function of the ignition timing. In this case, the presence / absence information of the ignition retard operation is added to the calculation unit of the final abnormal combustion determination value, and the abnormal combustion determination value is corrected with the correction coefficient only while the ignition retard is operating.

  A specific formula is shown below.

<Formula 3>
D1ATH = MDTH1 × KFIR
MDTH1: Abnormal combustion judgment value map search value KFIR: Ignition retard correction coefficient D1ATH: Final abnormal combustion judgment value KFIR is as follows.
(A) Condition: ignition retard operating (A) When condition satisfied: KFIR = TKFIR
(A) When the condition is not satisfied: KFIR = 1.0
TKFIR: ignition retard correction coefficient table search value Here, the correction coefficient is a function of the ignition timing because the required value varies depending on the ignition timing as shown in FIG.

  FIG. 12 shows a specific behavior of the final abnormal combustion determination value D1ATH, which is basically the same operation as FIG. 9, and will not be described.

  FIGS. 13 and 14 are flowcharts showing an example of the above-described combustion state diagnosis routine executed by the control unit 207.

A series of processes shown in the flowchart is repeatedly executed for each ignition. First, in step 801, the window passing time (the time required for rotating a predetermined crank angle)
Tw (i) is measured.

In step 802, the combustion state parameter D1A1 is calculated from <Equation 1>, and in step 803, it is checked whether or not the diagnosis region condition is satisfied. Here, when the diagnosis condition is not satisfied, the process proceeds to (3) in FIG. When the diagnosis area condition is satisfied, the process proceeds to step 804, and it is checked whether or not ignition retard is being performed. If not, the process proceeds to step 811 in FIG. 14, and the correction coefficient KFIR = 1.0 is set and the process proceeds to step 808. If it is being executed, it is checked in step 805 whether or not the correction coefficient calculation speed condition is satisfied. If not, the process proceeds to step 811. If it is satisfied, the process proceeds to step 806 to check the idle state. If it is not in the idle state, the process proceeds to step 811 in FIG. 14, and if it is in the idle state, the process proceeds to step 807 in FIG. Here, step 805 and step 806 are conditions for limiting the correction coefficient calculation region because there is no need to correct the abnormal combustion determination value during the high engine speed region and off-idle.

  In step 807, the correction coefficient is calculated according to <Expression 2> or <Expression 3>, and the final abnormal combustion determination value is calculated in Step 808, and the process proceeds to Step 809.

  Step 809 compares the combustion state parameter D1A1 calculated in Step 802 with the final abnormal combustion determination value D1ATH calculated in Step 808 to determine abnormal combustion (misfire). When D1A1 ≧ D1ATH is satisfied, Step 810 Count up one misfire counter and end. If not established, it is determined that the combustion is normal, and the process ends without passing through step 810 (does not increase the misfire count).

  Further, after the process is completed, the process is repeated again from step 801.

  Next, the second embodiment of the present invention will be described.

  Since the configuration of the system is the same as that of the first embodiment as shown in FIGS. 1 and 3 to 6, the description is omitted, and specific means will be described.

FIG. 15 is a functional block diagram showing the contents of the combustion state diagnosis executed by the control unit 207, and means 101 for measuring the time required for the crank angle plate 208 attached to the crankshaft to rotate a predetermined angle; Means 102 for calculating a pitch error correction amount, combustion state parameter calculation means 103 for calculating a combustion state parameter from the required time and the pitch error correction amount, and an abnormality for calculating an abnormal combustion determination value from the engine speed and engine load Combustion determination value calculation means 104 calculates a correction value for correcting the abnormal combustion determination value by the ignition retard amount and the engine speed or engine load, or a determination value for correcting by the ignition timing and engine speed or engine load. The corrected abnormal combustion determination value calculating means 108 for calculating, and the abnormality Based on the combustion condition parameter and the final abnormal combustion determination value, the final abnormal combustion determination value selection means 109 for selecting the final abnormal combustion determination value from the ignition retard operation presence / absence information, and the combustion determination value and the corrected abnormal combustion determination value. And abnormal combustion determination means 107 for determining the presence or absence of abnormal combustion such as misfire.

  FIG. 16 shows one of the correction methods. In addition to the conventional abnormal combustion determination value map having axes such as engine speed and engine load, the ignition retard amount or the ignition timing axis and rotation are added. This is a means for countermeasures against misfire detection leakage at the time of ignition retard operation by newly having a map having a number or a load axis and switching these search maps according to the presence / absence information of ignition retard.

  A specific formula is shown below.

<Formula 4>
D1ATH = MDTH
D1ATH: Final abnormal combustion determination value MDTH: Abnormal combustion determination value map search value MDTH is obtained from the following: (A) Condition: Fast idle ignition retard is operating (A) When condition is satisfied: MDTH = MDTHFIR
(A) When the condition is not satisfied: MDTH = MDTH1
MDTH1: Basic Abnormal Combustion Determination Value Map Search Value MDTHFIR: Corrected Abnormal Combustion Determination Value Map Search Value at Ignition Retardation FIG. 17 shows a specific behavior of the final abnormal combustion determination value D1ATH. Although the value searched from the abnormal combustion determination value map is used, when the ignition retard is entered, the search map is switched, and the final abnormal combustion determination value D1ATH decreases. Thus, the combustion state parameter D1A1 can exceed the final abnormal combustion determination value D1ATH, and misfire can be detected even during the ignition retard operation.

  18 and 19 are flowcharts showing an example of the above-described combustion state diagnosis routine executed by the control unit 207. FIG.

A series of processing shown in the flowchart is repeatedly executed for each ignition. First, in step 821, a window passing time (a time required for rotating a predetermined crank angle) Tw (i) is measured.

  In step 822, the combustion state parameter D1A1 is calculated from <Equation 1>, and in step 823, it is checked whether or not the diagnosis region condition is satisfied. Here, when the diagnosis condition is not satisfied, the process proceeds to (3) in FIG. When the diagnosis region condition is satisfied, the process proceeds to step 824, and it is checked whether ignition retard is being performed. If not, the process proceeds to 828 in FIG. 19, and the final abnormal combustion determination value D1ATH = MDTH1 is set, and the process proceeds to step 829. If it is being executed, it is checked in step 825 whether or not the correction map calculation rotational speed condition is satisfied. If not, the process proceeds to step 828, and if satisfied, the process proceeds to step 826 to check the idle state. If it is not in the idle state, the process proceeds to step 828 in FIG. 19, and if it is in the idle state, the process proceeds to step 827 in FIG. Here, step 825 and step 826 are conditions for limiting the search map switching region because there is no need to switch the final abnormal combustion determination value during the high engine speed region and off-idle.

  In step 827, the final abnormal combustion determination value D1ATH = MDTHFIR is set. Next, in step 829, the combustion state parameter D1A1 calculated in step 822 is compared with the final abnormal combustion determination value D1ATH calculated in step 827 or step 828. When the determination of (misfire) is made, if D1A1 ≧ D1ATH is satisfied, the misfire counter is incremented by one in step 830, and the process ends. If not established, it is determined that the combustion is normal, and the process ends without passing through step 830 (does not increase the misfire count). Further, after the process is completed, the process is repeated again from step 821.

1 is a schematic configuration diagram showing an embodiment of a combustion state diagnostic device according to the present invention together with an in-vehicle engine to which the embodiment is applied. The functional block diagram which shows the combustion condition diagnostic content which the control unit shown by FIG. 1 performs. The figure which showed the change with respect to the crank angle of the engine speed at the time of misfire. The figure which shows the change of the window passage time (A) at the time of cylinder # 1 misfire, and the combustion state parameter (B). The figure used for description of a misfire determination and the structure of a misfire count. The figure used for description of the cause of misfire detection leakage that occurs during idle ignition retard control. The figure which is provided for description of the coefficient which correct | amends the abnormal combustion determination value according to the amount of ignition retards during the ignition retard control of Example 1. FIG. The figure which shows one example of the coefficient which correct | amends abnormal combustion determination value according to the amount of ignition retards. The figure which shows the correction method of the last abnormal combustion determination value. The figure used for description of the coefficient which correct | amends the abnormal combustion determination value according to ignition timing during ignition retard control. The figure which shows one example of the coefficient which correct | amends an abnormal combustion determination value according to ignition timing. The figure which shows the correction method of the last abnormal combustion determination value. The flowchart which shows the front | former stage part of an example of the combustion state diagnostic routine which a control unit performs. The flowchart which shows the back | latter stage part of an example of the combustion state diagnostic routine which a control unit performs. The functional block diagram which shows the combustion condition diagnostic content which the control unit shown by FIG. 1 performs. The figure which is provided for description of the means for switching the final abnormal combustion determination value search map during the ignition retard control of the second embodiment. The figure which shows the search map switching method of the last abnormal combustion determination value. The flowchart which shows the front | former stage part of an example of the combustion state diagnostic routine which a control unit performs. The flowchart which shows the back | latter stage part of an example of the combustion state diagnostic routine which a control unit performs.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 101 Required time measurement means 102 Pitch error correction amount calculation means 103 Combustion state parameter calculation means 104 Abnormal combustion determination value calculation means 105 Determination value correction coefficient calculation means 106 Final abnormal combustion determination value calculation means 107 Abnormal combustion determination means 108 Correction abnormality Combustion judgment value calculation means 109 Final abnormal combustion judgment value selection means 200 Air cleaner 201 Ignition device 202 Fuel injection valve 203 Rotation angle sensor 204 Air flow sensor 205 Air-fuel ratio sensor 206 Catalyst 207 Control unit 208 Crank angle plate 209 Fuel tank 210 Fuel pump 211 Pressure regulator 212 Fuel piping system 213 Throttle valve 214 Combustion chamber # 1, # 2, # 3, # 4 Cylinder 220 Intake passage 230 Exhaust passage

Claims (9)

A required time measuring means for measuring a time required for the crankshaft to rotate at a predetermined angle; a combustion state parameter for detecting a combustion state of the engine from the required time; and a specific determination value for the combustion state parameter. In an engine combustion state diagnostic apparatus comprising a means for detecting the occurrence of abnormal combustion in comparison, from the torque at the ignition timing (hereinafter referred to as “MBT”) at which the output and the fuel consumption rate are the best An engine combustion state diagnosing device that corrects a determination value for detecting abnormal combustion when the combustion state parameter decreases due to a decrease.   The engine combustion state diagnosis apparatus according to claim 1, wherein the coefficient for correcting the abnormal combustion determination value is a function of a retard amount from an ignition timing of MBT.   The engine combustion state diagnosis apparatus according to claim 1, wherein the coefficient for correcting the abnormal combustion determination value is a function of ignition timing.   The engine combustion state diagnosis apparatus according to claim 1, wherein the map for searching for a determination value for detecting abnormal combustion is selected based on an ignition retard amount.   The engine combustion state diagnosis apparatus according to claim 1, wherein the abnormal combustion determination value search map is selected based on the presence or absence of ignition retard.   5. The engine combustion state diagnosis apparatus according to claim 3, wherein one of the abnormal combustion determination value maps has a function of an ignition retard amount and an engine speed or an engine load.   5. The engine combustion state diagnosis apparatus according to claim 3, wherein one of the abnormal combustion determination value maps has a function of ignition timing and engine speed or engine load.   The means for correcting the abnormal combustion judgment value with a coefficient corresponding to the ignition retard amount or the ignition timing and the means for selecting the judgment value search map are performed at a specific engine speed or less or a specific engine speed or more. An engine combustion state diagnostic apparatus according to any one of claims 1 to 6.   The means for correcting the abnormal combustion determination value with a coefficient corresponding to the ignition retard amount or the ignition timing and the means for selecting the abnormal combustion determination value map have a function of stopping by the off-idle determination or time or the number of ignitions. The engine combustion state diagnostic apparatus according to any one of claims 1 to 6, further comprising:

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