JPH04132862A - Misfire detecting device for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform accurate decision of a misfire throughout a wide range of an engine running region by detecting a given time ratio between front and rear given angle sections, based on a given crank angle and detecting a misfire from the time ratio. CONSTITUTION:A misfire detecting means M5 detects the running state of an engine by means of signals from a load detecting means M3 and a number of revolutions detecting means M4. A time ratio between the given times of front and rear given angle sections is calculated based on the reference position of a crank angle from a signal from a crank angle detecting means M2, and from the time ratio, a misfire is detected. A memory map to read the map value of a set time ratio is previously stored in a memory in a microcomputer. Through comparison of the time ratio with a map value responding to a running state, the misfire is detectable by using a proper decision value. This constitution specifies a detecting output generated due to a difference in the operation condition (, such as a load and the number of revolutions,) of an engine, improves detecting ability during the misfire, and simplifies constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a misfire detection device for an internal combustion engine for detecting a misfire caused by an abnormality in the ignition system of the internal combustion engine.

[Conventional technology]

Conventionally, as this type of device, for example, JP-A-6! ! -26
There is one disclosed in Japanese Patent No. 845. This system detects the internal cylinder pressure of the engine using a cylinder pressure sensor, determines the crank angle at which this cylinder pressure reaches its peak, and determines that the engine is normal when this peak position exists within a predetermined crank angle period. It is.

[Problem to be solved by the invention]

However, with such conventional devices, it is necessary to continuously measure the cylinder pressure at each crank angle for a predetermined period in order to detect the peak position of the cylinder pressure, making the device complex and difficult to operate under light load operating conditions. There are two peak values of in-cylinder pressure: compression top dead center and peak due to combustion, which is difficult to judge.
Further, there was a problem in that a misfire could not be determined if there was a peak before compression top dead center.

The present invention has been made to solve these problems, and is intended to enable accurate misfire determination over a wide range of engine operating ranges with a relatively simple configuration.

[Means to solve the problem]

This invention detects the time ratio required for the previous and subsequent predetermined angle sections with a predetermined crank angle as a reference, and detects a misfire from this time ratio.

[Effect]

In this invention, the ratio of time required for predetermined angle sections before and after a predetermined crank angle varies depending on the combustion state of the engine. Since the time ratio between fixed angles changes depending on the presence or absence of a misfire, a misfire is determined from the time ratio between the two angles.

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

FIG. 91 is a functional block diagram of the present invention. Further, FIG. 2 is a configuration diagram showing an embodiment of the present invention.

In Figures 1 and 2, Ml is the engine, M2 is the crank angle reference position (e.g. top dead center), and pulses at each angular position a predetermined angle (e.g. 46°A) before or after this reference position. This is a crank angle detection means that outputs. Crank angle detection means M2 is provided in engine M1 to detect crank rotation, for example, as shown in FIG.

M8 is a load detection means for detecting the engine load, such as the air flow meter M8.1° intake pipe pressure sensor M8.2 shown in FIG. 2 or the throttle valve opening sensor M8.8 for detecting the throttle valve opening. At least one of these can be used. Reference numeral M4 denotes a rotation speed detection means, which measures the cycle between predetermined crank angles based on, for example, a reference position signal of the crank angle detection means M2, and detects the rotation speed of the engine. M6 is a misfire detection means, which detects the operating state of the engine from the signals of the load detection means M8 and the rotational speed detection means M4, and further detects the front and rear positions based on the crank angle reference position from the signal of the crank angle detection means M2. A time ratio of the time required for each predetermined angle section is calculated, and a misfire is detected from this time ratio. The rotation speed detection means M4 and the misfire detection means M6 are, for example, a microcomputer M shown in FIG.
The IO includes an input interface ζ which inputs signals from the load detection means M8 and crank angle detection means M2, and an A/D converter and fixed timer which convert the input analog signals into digital signals. It consists of a single-chip microcomputer with a built-in timer counter (free-run counter) that counts up every clock, and circuits such as memory (ROM, RAM).

Next, the basic principle of the present invention will be explained.

Figure 8 shows a 4-stroke, 4-cylinder engine with a rotational speed of 11.
00Orp, the angular velocity when the throttle is fully open, and the time ratio Tv'Tte required for a predetermined crank angle before and after the compression top dead center; the in-cylinder pressure waveform of each cylinder is shown. Tv/Tt is the time ratio between the time TL required between the front predetermined angle (for example, 45 degrees Celsius) and the required time TU between the rear predetermined angles (for example, 46 degrees Celsius) with reference to the top dead center of the compression stroke.

This waveform shows 't41 * ij during a certain combustion cycle.
8.

ヰ4. This is when cylinder A1 misfires due to some reason, such as an abnormality in the ignition system, after each of the two cylinders burns normally. Now, for the 411 cylinder, the normally combusted one is set as fNa, its time ratio is TTJa/TLa, and the misfired one is set as 41b, and its time ratio is Ttr b / T.
If L b is TTJa/TLa, then TUb/
It can be seen that TLb is increasing. This is because during normal combustion, the angular velocity in the section TLa decreases during the compression stroke, and the angular velocity increases in the section TUa during the explosion stroke, whereas in the event of a misfire, TLb is the same as TLa. This is because the angular velocity further decreases due to misfire in the section where Ttrb occurs, and the required time Tab increases. As a result, in the event of a misfire, the time ratio TU/TL of misfire memory
misfire is detected by utilizing the fact that the time ratio of the same cylinder during normal combustion is greater than the time ratio of the same cylinder.

Next, examples of the present invention will be described.

FIGS. 4 and 6 are operation flow diagrams of the computer MIO showing the first embodiment of the present invention. In this embodiment, based on a predetermined crank angle (for example, top dead center of the compression stroke),
Between the front predetermined angle (for example, 46°C) and the rear predetermined angle (
For example, a misfire is detected from the time ratio by measuring the time required (for example, between 46° C. and A). Figure 4 (a) (b)
Then, the crank angle detecting means 1 reads the counter value that counts up every predetermined time clock every 45°C before the top dead center of the compression stroke and every top dead center of the compression stroke by interrupt processing using the signal 12, and stores the counter values in the memory. Buffer MB45゜M
Store it at TDC. This stored value indicates the time at 45°C before top dead center and at top dead center.

Furthermore, FIG. 5 is a flowchart of the interrupt calculation processing performed every 46°C after the top dead center of the compression stroke. S4゜S5,56
indicates the steps of the processing means. Sl reads the above-mentioned timer counter value at the time of this interrupt processing and stores it in the memory buffer MA45.

Then, in S2, the time ratio Tv / Tt is TU/TL
= (MA45-MTDC) / (MTDC-81B4
5).

Here, MA45-MTDC is 46 after top dead center from top dead center.
MTDC-MB46 shows the time required from 45°C A before top dead center to top dead center.

Then, in 54, it is determined whether the time ratio obtained in S2 is larger than a predetermined value corresponding to a misfire, and Y
6. If so, the process advances to S5, where it is determined that this cylinder has misfired, and the process ends. Further, if it is Nθ in S4, the process proceeds to S6, where it is determined that normal combustion is occurring in this cylinder, and the process is terminated. In this way, the time ratio of the time required between the front predetermined angle and the time required between the rear predetermined angle is detected using the predetermined crank angle as a reference, and a misfire is detected from this time ratio.

FIG. 6 is a flow diagram showing a second embodiment of the invention. In this embodiment, a misfire is determined based on the magnitude of the time ratio and a predetermined ratio predetermined based on the operating state of the engine. In this embodiment, as in the first embodiment, the timer counter value is stored in the memory buffer MB4δ as shown in FIG.
, M'l'D(:.Furthermore, Fig. 6 is a flowchart of the process performed at every predetermined angle (for example, every 46 degrees A) after the top dead center of the compression stroke, and S1, S2...S6 are The steps of the processing means are shown.Here, St and S2 are the same as those in Fig. 6, so their explanation will be omitted.In S8, a predetermined ratio memory map that is set in advance corresponding to the operating state of the engine is used to calculate the ratio corresponding to the operating state at that time. Read the map value of the set time ratio.

Here, the above memory map can be set, for example, as shown in FIG. 8, and is prepared in advance in the memory in the microcomputer Mlo shown in FIG. f42. The horizontal axis in FIG. 8 is the rotational speed N, Nl, N2. It is classified as N8. This rotational speed is detected by measuring the period between predetermined crank angles from the output of the crank angle detection means M8. Also, the vertical axis is a parameter indicating the engine load, for example, the intake air amount Q of the air flow meter that measures the intake air amount is used.
l, Q2. It is classified as QB. These zones are divided into zones, and setting ratios are assigned to the memories Pn, q corresponding to each zone. Here, n and q indicate the respective division numbers on the horizontal and vertical axes. The set ratio of the map zone is read out in accordance with the rotational speed and intake air amount at the time of reading out. Then, in S4,
If Yes, proceed to SL, determine that this cylinder is misfiring, and end the process. If the result in S4 is N, the process proceeds to S6, where it is determined that normal combustion is occurring in this cylinder, and the process ends. In this way, by comparing the time ratio with the map value corresponding to the operating state, a misfire can be detected using an appropriate judgment value for each operating state.

FIG. 7 is a flow diagram showing an eighth embodiment of the present invention. In this embodiment, map values predetermined according to the aforementioned operating conditions are learned and updated in a predetermined operating condition. In this embodiment, as in the first embodiment, the timer counter value is stored in the memory buffer MB45. as shown in FIG.
Store it in MTDC. Furthermore, FIG. 7 is a flowchart of a process performed at predetermined angle intervals (for example, every 46° C.A.) after the top dead center of the compression stroke, and since steps 81 to S6 are the same as FIG. 6, their explanation will be omitted. However, the memory map in S8 uses a non-rewritable memory (RAM). In S7, it is determined whether the conditions are such that learning can be performed (for example, during normal combustion, in a steady state that continues at a predetermined number of revolutions for a predetermined period of time, etc.).

If so, depending on the rotational speed and intake air amount at that time, the eighth
The map value of the corresponding operating state in the diagram is converted to the current time ratio TU.
/ Updated to the corrected value based on TL.

Store and end processing. If Nθ is determined in S7, the process ends. In this way, by correcting the predetermined map value according to the operating condition based on the learned value of Tυ/TL under the specified operating condition, it is possible to prevent misfires using the optimal judgment value without being affected by engine variations or changes over time. can be detected.

In the above embodiment, the map value is updated based on the boundary time ratio TV/TLO)h, but for example, the map value is updated based on the time ratio of a predetermined number of times in the past, other averaging processing values, or some kind of statistics. It is also possible to update and record the map value after additional processing as a new map value.

〔Effect of the invention〕

As described above, according to the first invention, the time ratio between the time required between the predetermined angle and the time required between the predetermined angle after the predetermined angle is detected based on the predetermined crank angle, and a misfire is detected based on this time ratio. Therefore, it is possible to normalize fluctuations in the detection output caused by differences in engine operating conditions (load speed, etc.), improve the detectability in the event of a misfire, and also make the configuration more compact.

Furthermore, according to the second aspect of the invention, since the time ratio is compared with a map value corresponding to the operating state, a misfire can be detected using an appropriate determination value for each operating state.

Furthermore, according to the eighth invention, the map value corresponding to the operating state is learned and corrected in a predetermined operating state, and the corrected value is compared with the time ratio, so it is optimal without being affected by engine variations or changes over time. A misfire can be detected using a judgment value.

[Brief explanation of drawings]

FIG. 1 is a functional block diagram showing the configuration of the present invention. Fig. 2 is a configuration diagram showing an embodiment of a device to which the present invention is applied, and Fig. 8 shows the angular velocity and time ratio Try/Tt at the time of misfire.
* Waveform diagram showing the relationship between ai internal pressure, Figure 4 is a flowchart showing the processing routine every 45°C before compression top dead center and every compression top dead center in one embodiment of this invention, and Figure 6 is a flowchart showing the processing routine for each compression top dead center in one embodiment of this invention. FIG. 6 is a flowchart showing a processing routine every 46°C after λ in the upper row of compression in one embodiment, and FIG. FIG. 7 is a flowchart showing a processing routine for every 46°C after compression top dead center in yet another embodiment of the present invention, and FIGS. FIG. Ml... Engine, M2... Crank angle detection means,
Ml...Load detection means, M4...Rotation speed detection means,
MS: misfire detection means Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (3)

[Claims] (1) The engine is characterized by comprising means for detecting the time ratio of the required time for each of the preceding and following predetermined angle sections with reference to a predetermined crank angle of the internal combustion engine, and means for determining a misfire from this time ratio. Misfire detection device for internal combustion engines. (2) A misfire is determined when the relationship between the time ratio and the set ratio stored in the memory corresponding to the operating state of the engine satisfies a predetermined relationship.
A misfire detection device for an internal combustion engine as described in . (3) Update and store the set ratio stored in the memory based on the detected time ratio, and determine that a misfire has occurred when the relationship between this stored value and the current time ratio satisfies a predetermined relationship. A misfire detection device for an internal combustion engine according to claim 2, characterized in that: