JPH04128537A - Misfire detection method of internal combustion engine - Google Patents

Abstract

PURPOSE:To simply and surely judge whether misfire id generated or not based on the result of judgement whether engine rotational speed is increased or not by successively detecting and mutually comparing the engine rotational speeds in the vicinity of the compression top dead center and the engine rotational speeds during transfer to the next compression top dead center. CONSTITUTION:The electronic controller 2 of an engine 1 is constituted of a center processing unit 3, a memory 4, an input interface 5, an output interface 6 and the like, and function for detecting misfire is provided. A signal N which indicates the compressed top dead center of each cylinder from a crank angle reference position sensor 7 is inputted to an input interface 5, and a signal P which corresponds with engine rotational speed is inputted from an electromagnetic pickup 8. In this case, the engine rotational speeds in the vicinity of the compression top dead center, and the engine rotational speeds during transfer to the next compression top dead center are detected successively, and also both engine rotational speeds are mutually compared, so as to judge whether the engine rotational speed is increased or not, and thereby it is judged whether the misfire is generated or not based on the result of judgement.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a misfire detection method for an internal combustion engine, which is applied to engines such as automobiles.

[Prior Art] Recently, it has been proposed to prevent deterioration of emissions, drivability, etc. by detecting misfires due to abnormalities in spark plugs, improper adjustment of air-fuel ratio, etc., and taking immediate action.

As a method for detecting a misfire, for example, as shown in FIGS. 9 and 10, the engine rotational speed is sequentially detected for each cycle, and the previously detected value ΔN is
There is a method of sequentially comparing et-1 and the latest value ΔNe +. When combustion is performed normally, as shown in FIGS. 9 and 11, the difference ΔNe l−I
If there is almost no change in ANe + and a misfire occurs, the difference ΔNe,
A significant change appears in -1-8he +.

This method focuses on the fact that the engine rotational speed is not always constant, but is slowest at compression top dead center and fastest during the subsequent combustion stroke.

Further, as prior art of the present invention, for example, JP-A-2-4
As shown in Japanese Patent No. 9955, engine rotational speeds are sequentially detected between combustion strokes, and the detected engine rotational speeds are sequentially compared.
Some systems identify the cylinder in which a misfire has occurred based on whether the difference exceeds a certain value.

Problems to be Solved by the Invention] However, according to the former configuration, it is necessary to constantly detect the maximum and minimum values of the engine rotation speed.
This increases the burden on electronic control devices and the like that play such a role.

Furthermore, in such a case, there is a high possibility that an erroneous determination will occur if a change occurs in the carrot rotational speed due to a difference in explosion combustion energy between the cylinders.

On the other hand, in the latter case, the engine rotation speed is detected between the combustion stroke and the combustion stroke itself, but the engine rotation speed in the Z region is a value close to the average value of the maximum value and the minimum value J. Become. For this reason, for example, stir fry.

If a misfire--combustion--misfire--one-combustion-year misfire occurs alternately between cylinders that experience different types of combustion, it becomes difficult to accurately detect the pressure of the misfire.

The present invention includes the following 1-. The purpose is to eliminate problems such as.

[Means for Solving the Problems] In order to achieve the above object, the present invention proposes the following means.

That is, the misfire detection method for an internal combustion engine according to the present invention is as follows:
The engine rotation speed near the compression top dead center and the engine rotation speed on the way to the next compression top dead center are sequentially tested, and both engine rotation speeds are compared to determine whether the engine rotation speed is increasing. 5, and based on the result of the determination, it is determined whether or not a misfire has occurred.

[Effects] When combustion is performed normally, the combustion energy increases rapidly after passing compression top dead center, so the engine speed always increases, and then the speed increases toward the next compression top dead center. gradually decreases. Therefore, in this case, the engine rotation speed on the way to the next compression top dead center will be faster than the engine rotation speed near the compression top dead center, and from the comparison results, it is clear that combustion will occur reliably in the combustion stroke. It is possible to determine what has happened.

On the other hand, when a misfire occurs, no combustion energy is generated, so the engine rotational speed does not increase but gradually decreases. In that case, the engine rotational speed on the way to the next compression top dead center will be lower than the engine rotational speed near compression top dead center, and it can be determined from the comparison result whether a misfire has occurred.

[Example j] Hereinafter, an example of the present invention will be explained using a 4-cylinder 4-stroke automobile.
A case where the present invention is applied to an engine will be described with reference to FIGS. 1 to 6.

An engine 1, which is an internal combustion engine schematically shown in FIG.
It is set so that ignition is performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder every 80° CA (crank angle), and an electronic control device 2 is provided.

The electronic control unit 2 includes a central processing unit 3, a memory 4,
Human power interface 5 and output interface 6
It is a microcomputer unit composed of the following, and has a function to detect misfires. As shown in FIG. 4, an N signal indicating the compression top dead center (compression TDC) of each cylinder is input to the human power interface 5 from a crank angle reference position sensor 7 built in a distributor (not shown) every 180oCA. At the same time, a P signal corresponding to the engine rotational speed is output from the electromagnetic pickup 8 at 36.
' It is entered for each CA.

The electromagnetic pickup 8 is similar to a conventional one in which a coil (not shown) is wound around the outer periphery of a magnetic iron core 8a, and the iron core 8a is arranged close to the outer periphery of a signal plate 9. The signal plate 9 has 20 teeth 9a at equal intervals on the outer circumference, and the crankshaft 10
It is fixed to the end of the. When the signal plate 9 rotates, the magnetic field generated in the iron core 8a is interrupted and an AC voltage is generated in the coil.The AC voltage is waveform-shaped by a waveform shaping circuit (not shown) and sent to the input interface 5. It is designed to be input as the P signal.

Further, the electronic control device 2 has built-in programs as schematically shown in FIGS. 2 and 3. Figure 2 shows
This is an interrupt routine every time the N signal is input, and in step 51, the N signal interrupt occurrence flag XNIRQ is set to 1, and the process proceeds to step 52.

In step 52, a combustion stroke occurrence counter CF is counted up, and the process proceeds to step 53. In step 53,
Determine whether or not the misfire determination start flag XMIS is set to 1. If it is set to 1, proceed to step 5.
6, and if not set to 1, step 54
Proceed to. In step 54, the combustion stroke occurrence counter CF
is cleared and the process proceeds to step 55. In step 55,
The misfire count counter MF is cleared and the process proceeds to step 56. In step 56, it is determined whether or not the value of the combustion stroke occurrence counter CF exceeds a certain value (for example, 400 times), and only if it does, the process proceeds to step 57. In step 57, the misfire count counter is set to a fixed value (for example, 8
1), and if so, proceed to step 58; if not, proceed to step 59.
Proceed to. In step 58, a fail determination is made to the effect that misfires have occurred at a rate exceeding a certain value, and the process proceeds to step 59.

In step 59, the misfire determination start flag XMIS is cleared and the process proceeds to step 60. In step 60, a combustion stroke occurrence counter CF and a misfire count counter MF are respectively cleared.

FIG. 3 shows an interrupt routine every time the P signal is input, and in step 71, the time TNE between P signals is measured as shown in FIG. 4, and the process proceeds to step 72. Step 72
Then, as shown in FIG. 4, the P signal generation counter NP is counted up and the process proceeds to step 73. Step 73
Then, it is determined whether or not the N signal interrupt generation flag XNIRQ is set to 1. If it is set to 1, the process proceeds to step 74; if it is not set to 1, the process proceeds to step 75. In step 74, the P signal generation counter NP is cleared and the process proceeds to step 75. Step 7
In step 5, it is determined whether or not the P signal generation counter NP is set to 0. If it is set to 0, the process proceeds to step 76, and if it is not set to 0, the process proceeds to step 77. In step 76, the time TNE between P signals is set to a predetermined address TNEO, and the process proceeds to step 77.

In step 77, the P signal generation counter NP is set to a constant value (
For example, it is determined whether or not 2) has been reached, and only if it has been reached, the process proceeds to step 78. In step 78, it is determined whether the difference between the latest P signal interval time TNE and the time set in the address TNEO exceeds the misfire judgment value X, and only if it does, the process proceeds to step 79. In step 79, the misfire determination start flag XMIS is set to 1, and the process proceeds to step 80. In step 80, a misfire frequency counter is counted up and the process proceeds to step 81. In step 81, the N signal interrupt occurrence flag XNIR
Clear Q.

According to such a configuration, in each cylinder, the engine rotation speed (time T) at a constant crank angle immediately after passing compression top dead center TDC, and the constant crank angle after passing compression top dead center TDC at a predetermined crank angle. and the engine rotational speed are sequentially detected, and both engine rotational speeds are sequentially compared (step 71).
~78).

Then, as schematically shown in FIG. 5, the compression top dead center TD
If the engine rotational speed midway through the passage is higher than the engine rotational speed immediately after passing C, or if it remains unchanged, combustion is occurring normally.

On the other hand, as schematically shown in FIG. 6, the compression top dead center TDC
If the engine rotation speed during the passage is lower than the engine rotation speed for a constant crank angle by more than a certain value (steps 78-79), it is determined that a misfire has occurred.

In other words, if a misfire occurs due to an abnormality in the spark plug 11 or improper adjustment of the air-fuel ratio, combustion energy will not be generated from that cylinder, so the engine rotational speed will decrease as the engine moves to the next compression top dead center TDC. will decrease. In such a case, the number of misfire occurrences is counted (step 80), and the cylinder in which the misfire occurred is identified from the cylinder discrimination flag. Cylinder discrimination can be performed from the information if the ignition timing is controlled, and if the distributor or the like is equipped with a cylinder discrimination sensor, it is possible to discriminate the cylinder from the signal.

Such misfire detection diagnosis is repeatedly performed during operation, and if misfires occur more than a predetermined number of times within a certain number of combustions (for example, 400), a fail judgment is made to that effect (step 56). ~58). The fail judgment result can be displayed, for example, by a diagnostic lamp connected to the electronic control device 2 in advance, or by a tester or the like connected to a diagnostic output terminal provided in the electronic control device 2. I will do it.

Therefore, according to the detection method configured as below,
It is possible to reliably detect the speed difference between the engine rotational speed when combustion occurs and the engine rotational speed when a misfire occurs, and also to determine whether a misfire has occurred based on the detection result. It is possible to reliably determine whether As a result, the occurrence of a misfire can be promptly dealt with, and deterioration of emissions and drivability can be effectively suppressed. Moreover, according to this detection method, the engine rotation speed immediately after compression top dead center in each cylinder and the engine rotation speed on the way to the next compression top dead center are sequentially detected and compared. Therefore, control can be performed relatively easily, and at the same time, there is no need to increase the burden or increase the capacity of the electronic control device 2.

Next, in order to further clarify the misfire detection method according to the present invention, it will be explained with reference to FIGS. 7 and 8. Figures 7 and 8 show a 18°
This is the case where the engine rotational speed (indicated by the passing time T) for each CA (crank angle) is detected. As can be determined from Fig. 7, when combustion is performed normally in each cylinder, the engine rotational speed increases midway between compression top dead center TDC due to generation of combustion energy (passing time TDC). (becomes shorter), the engine rotational speed gradually decreases as it moves toward the next compression top dead center TDC side. In this case, it is shown that combustion is reliably performed in each cylinder during the combustion stroke.

FIG. 8 shows a case where a misfire is intentionally caused to occur in a specific cylinder. In this case, although some rotational fluctuations occur overall, the engine rotational speed in the cylinder where the misfire occurred becomes even slower as it moves from the time of the misfire to the next compression (TDC) side. (passage time T becomes longer). In this case, a misfire has occurred in the first cylinder.

Note that the present invention is effectively applicable not only to multi-cylinder engines but also to single-cylinder engines.

Further, in the above embodiment, the engine rotation speed immediately after the compression top dead center is detected, but the engine rotation speed immediately before the compression top dead center may be detected and compared with the intermediate engine rotation speed.

[Effects of the Invention] Since the present invention has the above-described configuration, it is possible to easily and reliably detect whether a misfire has occurred without complicating the control. As a result, when a misfire occurs, misfire prevention measures can be taken immediately, and deterioration of emissions, drivability, etc. due to a misfire can be effectively avoided.

[Brief explanation of the drawing]

1 to 6 show one embodiment of the present invention5, FIG. 1 is an overall configuration diagram, FIGS. 2 and 3 are flowcharts schematically showing control procedures, and FIG. 4 is a control mode. 5 and 6 are action explanatory diagrams. FIG. 7 and FIG. 8 are reference views according to the present invention. FIG. 9 to FIG. 11 are explanatory views of the operation in the conventional example, respectively. 1... Internal combustion engine (automobile engine) 2... Electronic control device 7... Crank angle reference position sensor 8... Electromagnetic pickup 9... Signal plate 10... Crankshaft

Claims (1)

[Claims] The engine rotation speed near the compression top dead center and the engine rotation speed on the way to the next compression top dead center are sequentially detected, and both engine rotation speeds are compared to determine whether the engine rotation speed is increasing. 1. A method for detecting a misfire in an internal combustion engine, characterized in that it is determined whether or not a misfire has occurred based on the determination result.