JP2795062B2 - Misfire detection method due to crankshaft rotation fluctuation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a misfire due to fluctuations in crankshaft rotation, and more particularly, to a method for detecting misfires caused by the rate of change in crankshaft rotation vibrating once a misfire state occurs. The present invention relates to a misfire detection method capable of accurately detecting the presence or absence of a misfire by removing an error.

[0002]

2. Description of the Related Art During operation of an internal combustion engine, if a misfire state occurs in which combustion in a cylinder is not performed normally due to a failure of a fuel injection device or the like, the exhaust gas characteristics of the internal combustion engine deteriorate.
Therefore, conventionally, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2-30954, information corresponding to the number of rotations is calculated from a cycle for each predetermined crank angle corresponding to each cylinder of the engine, and a change amount or a change rate of this information is calculated. Detects the misfire condition of the engine,
The fuel supply to the cylinder where misfire has been confirmed has been stopped. This type of misfire detection method focuses on the fact that when a misfire occurs in a cylinder, the rotational speed (angular speed) of the crankshaft decreases due to a decrease in the torque output of the internal combustion engine. When the rate of change in rotational speed falls below the reference value and becomes negative while repeatedly detecting the rate of change in speed (angular acceleration), occurrence of misfire is determined.

According to Japanese Patent Application Laid-Open No. 2-49955, the rotational angular velocity of the internal combustion engine and 1 as a reference angular velocity (determination reference value) are calculated for each ignition interval in accordance with the combustion stroke of the internal combustion engine. If misfire detection is performed based on the deviation from the rotational angular velocity before ignition, that is, rotation fluctuation, misfire cannot be accurately detected when accidental misfire occurs or misfire occurs at a rate of about once every several revolutions. Sometimes. Therefore, in Japanese Patent Application Laid-Open No. 2-49955, the reference angular velocity, that is, the determination reference value is updated as needed.

[0004]

However, once a misfire state has occurred in the internal combustion engine, the crankshaft will remain in the crankshaft for a while after the misfire state has occurred due to the resonance between the internal combustion engine and the drive system connected to the internal combustion engine. The rate of change of the rotational speed may increase or decrease in an oscillatory manner. In this case, even if the misfire state does not actually occur, the rate of change of the crankshaft rotational speed may fall below the reference value for misfire detection, and the misfire state may be erroneously detected.

Accordingly, the present invention eliminates a detection error in misfire detection caused by a change in the crankshaft rotation change rate after a misfire state once occurs, and accurately detects the presence or absence of misfire. An object of the present invention is to provide a misfire detection method which can be performed and does not require special hardware.

[0006]

In order to achieve the above object, a crankshaft rotation speed change rate corresponding to each cylinder of an internal combustion engine is periodically calculated, and a calculation cycle corresponding to a cylinder targeted for misfire detection is calculated. In the method for detecting misfire due to crankshaft rotation fluctuation, which detects the occurrence of misfire in the cylinder when the rate of change of the crankshaft rotation speed falls below the determination reference value, the present invention provides a method for detecting a misfire immediately after a calculation cycle corresponding to a cylinder to be misfired. When the first condition that the crankshaft rotation speed change rate in the calculation cycle of the above exceeds the sum of the crankshaft rotation speed change rate and the first threshold value in the corresponding calculation cycle is not satisfied, or When the second condition that the crankshaft rotation speed change rate in the calculation cycle immediately before the cycle exceeds the sum of the crankshaft rotation speed change rate in the corresponding calculation cycle and the second threshold value is not satisfied. Preferably, the rate of change of the crankshaft rotational speed in the calculation cycle corresponding to the cylinder for which misfire is to be detected is replaced with a value of zero, thereby filtering the calculated change rate in the cycle corresponding to the cylinder to be detected. And

[0007]

During operation of the internal combustion engine, for example, a time interval from the entry to the departure to the crankshaft rotation angle region corresponding to each cylinder is detected by a crank angle sensor, and a change in the crankshaft rotation speed is detected based on the detected time interval. Calculate the rate. While repeating the calculation of the change rate, when the first condition that the current change rate exceeds the sum of the previous change rate and the first threshold is not satisfied, or when the change rate in the calculation cycle two times before is equal to the previous change rate and the second change rate. When the second condition of exceeding the sum with the threshold value is not satisfied, it is determined that the vibration of the rate of change of the crankshaft rotational speed after the occurrence of the misfire state has affected the rate of change in the previous cycle. Filter the calculated rate of change. For example, filtering is performed by setting the calculated change rate to a value of zero. As a result, the influence of the vibration of the rate of change is removed, and the occurrence of misfire is prevented from being detected by mistake.

On the other hand, both the first and second conditions are satisfied,
Therefore, if it is determined that the change rate of the crankshaft rotation speed has changed suddenly in the previous cycle, it is determined that the change in the change rate is not due to the influence of the change rate vibration after the occurrence of the misfire state, and the calculated change rate in the previous calculation cycle is determined. Without filtering, misfire detection is performed using the calculated change rate itself. As a result, when the calculated change rate falls below the reference value for misfire detection, misfire occurrence is detected.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for detecting misfire due to fluctuations in crankshaft rotation according to one embodiment of the present invention will be described below. An apparatus for performing the misfire detection method according to the present embodiment is mounted on, for example, a six-cylinder engine (not shown) as an internal combustion engine.
As shown in the figure, the controller 10, the crank angle sensor 2
0 and a cylinder discrimination sensor 30 are provided as main elements.

Referring to FIG. 2, the crank angle sensor 20
Has a rotating member 21 rotatably mounted integrally with the camshaft 1 that rotates in synchronization with a crankshaft (not shown) of the engine, and a detecting unit 22 disposed facing the rotating member 21. The first, second and third vanes 21a, 21b projecting in the radial direction of the cam shaft
And 21c are formed, and the vane 21 is detected by the detection unit 22.
When the passage of a, 21b or 21c is detected optically or electromagnetically, a pulse output is generated. First to third vanes 21a, 21b and 21c
Have circumferential lengths each corresponding to a certain angle of rotation of the crankshaft and are spaced circumferentially apart from each other at a predetermined angular interval, so that between corresponding ends of adjacent vanes Is 120 degrees. However, in practice, due to a structural error of the crank angle sensor 20, particularly an error in manufacturing and mounting the vanes 21a, 21b and 21c, the angular interval between the ends of the adjacent vanes is exactly 12
It is not always 0 degree, and generally has an angle interval error of about 1 degree or less.

The cylinder discriminating sensor 30 is mounted on the camshaft 1 so as to be rotatable integrally therewith. The camshaft 1 corresponds to one cylinder while the crankshaft makes two revolutions and the camshaft 1 makes one revolution. Each time the rotational position is taken, a pulse output is generated. Controller 10
The processor 11 functions as a main element of the misfire detection device and executes normal various engine controls. A processor 11 for executing various control programs, a read-only memory 12 storing the control programs, and a temporary storage of data. And the like for a random access memory 13. The processor 11 is connected via an input circuit 14 to various sensors and switches (partially not shown) such as a crank angle sensor 20, a cylinder discrimination sensor 30, an ignition switch 40, an intake air amount sensor, an intake air temperature sensor, and a water temperature sensor. And the output of the fuel injection valve 50
Are connected to various drive circuits (only those corresponding to the elements 50 and 60 are denoted by reference numerals 51 and 61) for driving the warning lamp 60 and the like.

In the apparatus of this embodiment mounted on a six-cylinder engine in which the ignition operation is performed in the order of the cylinder number, for example, the end (front end 21c 'or rear end) of the third vane 21c is detected by the detection unit 22.
Is passed through the first crankshaft rotation angle region corresponding to one of the first cylinder and the fourth cylinder (preferably, mainly the expansion stroke in the one cylinder) of the first cylinder group. When the shaft enters, the first vane 21
When the end of a passes through the detection unit 22, the crankshaft
It separates from the rotation angle region. Similarly,
When passing through the end of the first vane 21a, the first vane 21a enters the second crankshaft rotation angle region corresponding to one of the second and fifth cylinders forming the second cylinder group and the second vane 21
b when the vehicle passes through the end of the second vane 21b, and then enters the third crankshaft rotation angle region corresponding to one of the third and sixth cylinders forming the third cylinder group when passing through the end of the second vane 21b. At the same time as the third vane 21c passes through the end of the third vane 21c. The identification of the first cylinder and the fourth cylinder, the identification of the second cylinder and the fifth cylinder, and the identification of the third cylinder and the sixth cylinder are performed based on the output of the cylinder determination sensor 30.

Hereinafter, the operation of the misfire detection device having the above configuration will be described. During the operation of the engine, the processor 11 periodically and repeatedly executes the misfire detection process shown in FIG. 3 while sequentially inputting the pulse output from the crank angle sensor 20 and the pulse output from the cylinder discrimination sensor 30. Processor 11
Starts a misfire detection processing cycle each time the pulse output of the crank angle sensor 20 is input. In each detection cycle, the processor 11 first determines the order of the crank angle sensor pulse output among the crank angle sensor pulse outputs sequentially input after the input point of the pulse output of the cylinder determination sensor 30. I do. This allows
The order of the cylinder corresponding to the input crank angle sensor pulse output is identified (step S).
1). Preferably, a cylinder that is mainly performing an expansion stroke (output stroke) at the present time is identified as an identification cylinder.

When the processor 11 determines the entry into the crankshaft rotation angle region corresponding to the identified cylinder group m (m is 1, 2, or 3) in accordance with the input of the pulse output of the crank angle sensor 20, A period measurement timer (not shown) is restarted. The identification cylinder group m includes the cylinder identified in step S1. Crank angle sensor 20
When the next pulse output is input from, the processor 11
Departure from the crankshaft rotation angle region corresponding to the discriminating cylinder group m is determined, the timing operation of the period measurement timer is stopped, and the time measurement result is read (step S2). This time measurement result is a time interval Tm (n) from the point of entry into the crankshaft rotation angle region corresponding to the identified cylinder group m to the point of departure from the region, that is, two predetermined crank angles corresponding to the identified cylinder group. Period Tm (n) determined by
Is represented. Here, the suffix n in the cycle Tm (n) indicates that the cycle corresponds to the n-th (current) ignition operation in the identification cylinder. Further, the cycle Tm (n) is a cycle between the 120-degree crank angles of the discriminating cylinder group in the six-cylinder engine, and more generally, (720 /
N) degree crank period.

Then, the processor 11 calculates a correction coefficient KLm (n) related to the identified cylinder group m by an equation KLm (n) = in order to eliminate a cycle measurement error due to a variation in vane angle intervals in vane manufacturing and installation. a · KLm (n-1) + (1-a)
Calculate according to KLm (step S3). Here, the symbol a is a filter constant stored in the memory 12 in advance and takes a value of 0 or more and 1 or less. Symbol KLm (n-1)
Represents a correction coefficient related to the identified cylinder group m calculated in the previous detection cycle and stored in the memory 13;
KLm represents a value calculated according to the formula KLm = Tm (n) ÷ (T (n) / 3). Here, the symbol Tm (n) represents the currently detected cycle between the 120 ° crank angles of the identified cylinder group m, as described above. The symbol T (n) is the sum of the cycles between the 120-degree crank angles of the first to third cylinder groups measured successively in the previous two detection cycles and the current detection cycle, that is, the cycle between the 360-degree crank angles (T (n) ) = T1
(n) + T2 (n) + T3 (n)). If the engine speed is constant, the value T (n) / 3 obtained by dividing the 360-degree crank angle cycle by the value 3 is equal to the accurate 120-degree crank angle cycle when there is no error in the vane angle interval. Therefore,
The calculated value KLm indicates the ratio between the accurate 120-degree crank angle cycle and the 120-degree crank angle cycle of the identified cylinder group m.

Further, the processor 11 calculates the average angular velocity ωn (= 120 degrees / Tn) of the crankshaft in the cycle from the 120-degree inter-crank period Tn (= Tm (n)) measured in step S2 of the current detection cycle. At the same time, the period Tn-1 and the average angular velocity ωn-1 measured and calculated in the previous detection cycle and stored in the memory 13 are read out. Next, the processor 11 calculates the measured values Tn and Tn-1 and the calculated value ω
By using the correction coefficient KLm (n) calculated in step 3 and n, ωn−1, the average angular acceleration Dω of the crankshaft in the 120 ° inter-crank cycle of the current detection cycle is calculated by the equation Dω = K
Lm (n) · (ωn−ωn-1) ÷ ｛(1/2) · (Tn + Tn−
1) Calculate according to｝ (step S4). Here, the symbol D is a differential operator symbol and represents d / dt. In this way, the crankshaft angular acceleration is obtained based on the measurement cycle corrected using the correction coefficient KLm (n).

Next, the processor 11 sequentially determines whether or not the following two conditions are satisfied (step S).
5 and S6). (1) Crankshaft average angular acceleration Dωn in the current calculation cycle
Is larger than the sum of the angular acceleration Dωn-1 of the previous cycle and the first threshold value k1. More generally, the crankshaft rotation speed change rate Dωn in the calculation cycle immediately after the calculation cycle corresponding to the cylinder whose misfire is to be detected is determined by the change rate Dωn-1 of the corresponding calculation cycle and the first threshold k1. Greater than the sum of

(2) Angular acceleration Dωn-2 in the calculation cycle two times before
Is larger than the sum of the previous angular acceleration Dωn-1 and the second threshold value k2. More generally, the rate of change of the crankshaft rotation speed Dωn−2 in the calculation cycle immediately before the corresponding calculation cycle.
Is larger than the sum of the corresponding change rate Dωn-1 of the calculation cycle and the second threshold value k2. The processor 11 calculates a value Dω obtained by subtracting the previous angular acceleration Dωn-1 from the current angular acceleration Dωn.
When it is determined in step S5 that n-Dωn-1 is equal to or less than the first threshold value k1 and the first condition is not satisfied, or a value Dωn obtained by subtracting the previous angular acceleration Dω-1 from the angular acceleration Dωn-2 before the previous rotation. If it is determined in step S6 that -2-2-Dωn-1 is equal to or smaller than the second threshold value k2 and the second condition is not satisfied, the vibration of the crankshaft angular acceleration after the occurrence of the misfire state (see FIG. 4) is determined in the previous cycle. Judging that it is affecting the angular acceleration of
The calculated angular acceleration Dωn-1 in the previous cycle is replaced with a value “0” (step S7). As a result, the calculated angular acceleration Dωn−1 in the previous cycle is filtered, the influence of the vibration of the angular acceleration is removed (see FIG. 5), and the occurrence of misfire is prevented from being erroneously detected. In FIG. 5, the decrease in angular acceleration at the number of ignitions of 5, 13, and 21 is caused by the occurrence of misfire.

On the other hand, both the first and second conditions are satisfied,
Therefore, in the previous cycle, the crankshaft average angular acceleration Dω
If it is determined that n-1 has changed suddenly, it is determined that the change in angular acceleration is not due to the influence of angular acceleration vibration after the occurrence of the misfire state, and the calculated angular acceleration Dωn-1 in the previous calculation cycle is filtered. Absent. Next, the processor 11
When both the first and second conditions are satisfied, the value calculated in step S4 is used, while when the first or second condition is not satisfied, the previous average angular acceleration Dωn−1 that was set to the value “0” in step S7. Then, a magnitude relationship between the value and the reference value k3 for misfire determination stored in advance in the memory 12 is determined (step S8). Note that the determination reference value k3 is set to a negative value. When it is determined that the angular velocity Dωn-1 is smaller than the determination reference value k3, the processor 11 sends a drive signal of, for example, an H level to the lamp drive circuit 61 to turn on the warning lamp 60, thereby turning the warning lamp 60 off by one. A warning is issued that a previous misfire detection target cylinder has misfired (step S
9) Further, the fact that a misfire has occurred in the cylinder immediately before the identified cylinder determined in step S1 is stored in the memory 13 (step S10). On the other hand, if the average angular acceleration Dωn-1 of the crankshaft is equal to or larger than the determination reference value k3, step S8
When the determination is made, the processor 11 sends out, for example, an L-level drive signal to turn off the warning lamp 60, and notifies that no misfire has occurred in the misfire detection target cylinder (step S11).

After the storage of the misfiring cylinder in step 10 or the turning off of the warning lamp in step S11, the processor 1
1 waits for the input of the next pulse output from the crank angle sensor 20, and when the pulse output is input, the processing of FIG. 3 is restarted. Although the first to third embodiments have described the case where the present invention is applied to a six-cylinder engine, the present invention can be applied to various engines such as a four-cylinder engine. Further, in the above embodiment, in the misfire detection process (FIG. 3), the correction coefficient is calculated to remove the cycle measurement error due to the variation of the vane angle interval, and the crankshaft angular acceleration Dω is calculated using the correction coefficient. The calculation of the angular acceleration based on the coefficient calculation and the correction coefficient is not essential.

[0021]

As described above, the rate of change of the crankshaft rotational speed corresponding to each cylinder of the internal combustion engine is calculated periodically,
In a misfire detection method based on crankshaft rotation fluctuation for detecting misfire occurrence in a cylinder when the rate of change in crankshaft rotation speed in a calculation cycle corresponding to a cylinder targeted for misfire detection falls below a determination reference value, the present invention A first variation that the crankshaft rotation speed change rate in the calculation cycle immediately after the calculation cycle corresponding to the misfire detection target cylinder exceeds the sum of the crankshaft rotation speed change rate in the corresponding calculation cycle and a first threshold value. When the condition is not satisfied, or the crankshaft rotation speed change rate in the calculation cycle immediately before the corresponding calculation cycle exceeds the sum of the crankshaft rotation speed change rate in the corresponding calculation cycle and a second threshold value. When the second condition is not satisfied, preferably, the rate of change of the crankshaft rotational speed in the calculation cycle corresponding to the cylinder for which misfire is to be detected is replaced with a value of zero, so that Since the calculated change rate in the corresponding cycle is filtered, the detection error in the misfire detection caused by the crankshaft rotation change rate fluctuating vigorously after the misfire state once occurs is removed, The presence or absence of a misfire can be accurately detected, and no special hardware is required for this.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram showing an apparatus for implementing a misfire detection method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a crank angle sensor of the device shown in FIG.

FIG. 3 is a flowchart showing a misfire detection process executed by the controller of FIG. 1;

FIG. 4 is a graph illustrating an oscillating increase / decrease change in crankshaft average angular acceleration associated with occurrence of a misfire state.

FIG. 5 is a graph showing a change in the average crankshaft angular acceleration when a filter process for the average crankshaft angular acceleration is executed in the misfire detection process of FIG. 3 to remove the vibration shown in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Camshaft 10 Controller 11 Processor 20 Crank angle sensor 30 Cylinder discrimination sensor 40 Ignition switch 60 Warning lamp

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasuhisa Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (72) Inventor Mitsuhiko Yanagisawa 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Hiroyuki Nakashima 5-33-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (56) References JP-A-4-116246 (JP, A) JP-A-2-291476 (JP, A) JP-A-2-30954 (JP, A) JP-A-4-91344 (JP, A) JP-A-2-146245 (JP, A) (58) Int.Cl. ⁶ , DB name) F02D 45/00

Claims (2)

(57) [Claims] 1. A crankshaft rotation speed change rate corresponding to each cylinder of an internal combustion engine is periodically calculated, and a crankshaft rotation speed change rate in a calculation cycle corresponding to a misfire detection target cylinder is determined as a determination reference value. In the misfire detection method based on crankshaft rotation fluctuation for detecting the occurrence of misfire in the cylinder when the engine speed falls below, the rate of change of the crankshaft rotation speed in the calculation cycle immediately after the calculation cycle corresponding to the cylinder for which misfire is to be detected is determined by the above-described method. When the first condition that the crankshaft rotation speed change rate in the calculation cycle to be performed exceeds the sum of the first threshold value and the crankshaft rotation speed change rate in the calculation cycle immediately before the corresponding calculation cycle is not satisfied, When the second condition that exceeds the sum of the change rate of the crankshaft rotation speed and the second threshold value in the corresponding calculation cycle is not satisfied, the clutch in the calculation cycle corresponding to the cylinder whose misfire is to be detected is determined. A method for detecting misfire due to crankshaft rotation fluctuation, characterized by filtering the calculation result of the rotation speed change rate of the crankshaft. 2. When the first condition or the second condition is not satisfied, a crankshaft rotation speed change rate calculated in a calculation cycle corresponding to the cylinder whose misfire is to be detected is replaced with a value of zero. 2. The method for detecting misfire due to crankshaft rotation fluctuation according to claim 1, wherein a filter is applied.