JP2836421B2 - 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 in which the angular acceleration of a crankshaft is increased or decreased due to the occurrence of a misfire state. The present invention relates to a misfire detection method capable of accurately detecting the occurrence of a misfire.

[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, as disclosed in JP-A-2-30954 and the like,
Information corresponding to the number of revolutions is calculated based on a cycle for each predetermined crank angle corresponding to each cylinder of the engine, and a misfire state of the engine is detected based on a change amount or a change rate of this information. 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 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 angular acceleration may increase or decrease in vibration. In this case, even if the misfire state does not actually occur, the crankshaft angular acceleration may fall below the determination reference value for misfire detection, and the misfire state may be erroneously detected. As described above, according to the conventional method of immediately detecting the occurrence of a misfire state when a decrease in the angular velocity or the like is detected based on the comparison result of the angular velocity or the angular acceleration of the crankshaft and the determination reference value, it is possible to accurately determine whether or not the misfire has occurred. May not be detected.

Therefore, the present invention can accurately detect the presence or absence of a misfire even when the angular acceleration of the crankshaft increases and decreases due to the occurrence of a misfire state,
Moreover, an object of the present invention is to provide a misfire detection method that does not require special hardware.

[0006]

In order to achieve the above object, a parameter value representing a crankshaft angular acceleration corresponding to each cylinder of an internal combustion engine is repeatedly calculated, and based on the calculated parameter value, a parameter for a cylinder to be subjected to misfire detection is calculated. In a misfire detection method based on crankshaft rotation fluctuation for detecting the presence or absence of a misfire, the misfire detection method according to one aspect of the present invention is configured such that a calculated parameter value corresponding to a misfire detection target cylinder falls below a first determination value , Immediately before the ignition operation to be performed in the misfire detection target cylinder, it is determined whether or not a first determination condition that a decrease by a first predetermined change amount or more compared to a calculated parameter value corresponding to a preceding cylinder to be ignited is satisfied. And the calculated parameter value corresponding to the succeeding cylinder to be ignited immediately after the ignition operation to be performed in the misfire detection target cylinder exceeds the second determination value, or , It is determined whether or not the second determination condition referred to have increased the second predetermined change amount or more than the calculated parameter value corresponding to the misfire detection target cylinder is established, the first
And when both the second determination condition and the second determination condition are satisfied, the occurrence of a misfire in the misfire detection target cylinder is detected.

A misfire detection method according to another aspect of the present invention provides a method for calculating a misfire detection parameter corresponding to a first misfire detection target cylinder to be ignited first among two misfire detection target cylinders to be successively ignited. The value is smaller than the first determination value, or the first predetermined value is compared with the calculated parameter value corresponding to the preceding cylinder to be ignited immediately before the ignition operation to be performed in the first misfire detection target cylinder. It is determined whether or not a first determination condition that the amount of change has decreased by more than the amount of change is satisfied, and the calculated parameter value corresponding to the second cylinder targeted for misfire detection is determined as the calculated parameter value corresponding to the first cylinder targeted for misfire detection. It is determined whether or not a second determination condition that the amount has decreased by a second predetermined change amount or more is satisfied, and the ignition operation is performed immediately after the ignition operation to be performed in the second misfire detection target cylinder. Calculation parameters corresponding to the line cylinder A third determination condition that the data value exceeds the second determination value or increases by a third predetermined change amount or more compared to the calculated parameter value corresponding to the second misfire detection target cylinder is satisfied It is determined whether or not to perform
Further, when all of the third determination conditions are satisfied, the occurrence of misfire in the first and second misfire detection target cylinders is detected.

[0008]

During operation of the internal combustion engine, for example, a time interval from the entry to the exit of the crankshaft rotation angle region corresponding to each cylinder is detected by a crank angle sensor, and the angular acceleration of the crankshaft is determined based on the detected time interval. Is calculated. In a mode in which one cylinder at a time is set as a misfire detection target, the parameter value corresponding to the misfire detection target cylinder is repeated while repeating such parameter value calculation.
With less than the first determination value, the first determination condition as compared with the parameter value corresponding to the preceding cylinders called decreased first predetermined change amount or more, it is determined whether or not established. Note that the first determination condition is typically satisfied when the crank angular acceleration is reduced due to misfire. Further, whether the parameter value corresponding to the following cylinder exceeds the second determination value,
Alternatively, it is determined whether or not a second determination condition that the parameter value has increased by a second predetermined change amount or more compared to the parameter value corresponding to the misfire detection target cylinder is satisfied. Note that the second determination condition is typically satisfied when returning from the misfire state to the normal combustion state. Then, only when both the first and second determination conditions are satisfied, therefore, the misfire state is firstly confirmed, and then, only when the return from the misfire state to the normal combustion state is confirmed, the misfire detection target Detects misfires in cylinders.

As described above, once a misfire condition occurs, the angular acceleration of the crankshaft increases and decreases in a vibrating manner. FIG.
FIG. 4 illustrates the vibrational change of the crankshaft angular acceleration caused by the misfire when the misfire occurs at the fifth, thirteenth, and twenty-first ignition times. When the angular acceleration of the crankshaft is vibratingly changing as shown in FIG. 1, the parameter value corresponding to the misfire detection target cylinder decreases as compared with the parameter value corresponding to the preceding cylinder, and the first The determination condition may be satisfied. Alternatively, the second determination condition may be satisfied, for example, because the parameter value of the following cylinder increases compared to the parameter value of the misfire detection target cylinder.
On the other hand, even during the vibration change of the angular acceleration of the crankshaft, if the misfire does not actually occur in the misfire detection target cylinder, both the first and second determination conditions are hardly satisfied. In other words, when it is determined whether or not the two determination conditions are simultaneously satisfied, no erroneous detection occurs even if the crankshaft angular acceleration vibrates due to the previously generated misfire, and the occurrence of misfire is overlooked. Nothing to do.

In another mode in which two cylinders are detected as misfires at a time, the parameter value corresponding to the first misfire detection target cylinder falls below the first judgment value while repeating the above-described parameter value calculation. Or, it is determined whether or not a first determination condition that the amount of change has decreased by a first predetermined amount or more compared to the parameter value corresponding to the preceding cylinder is satisfied. It is determined whether there is a high probability that a misfire has occurred in the cylinder. Next, a second determination condition that the parameter value corresponding to the second misfire detection target cylinder has decreased by a second predetermined change amount or more compared to the parameter value corresponding to the first misfire detection target cylinder is satisfied. Then, it is determined whether or not there is a high probability that a misfire has occurred in the second cylinder to be misfired. Further, the parameter value corresponding to the following cylinder exceeds the second determination value, or
It is determined whether or not a third determination condition that the amount of change has increased by a third predetermined amount or more compared to the parameter value corresponding to the second misfire detection target cylinder is satisfied, thereby returning to a normal combustion state. It is determined whether or not. Then, when all of the first, second, and third determination conditions are satisfied, the occurrence of misfire in the two cylinders for which misfire is to be detected is detected. By determining whether the three determination conditions are simultaneously satisfied or not, the presence / absence of a misfire state in the cylinder targeted for misfire detection and the presence / absence of return to the normal combustion state are determined in the same manner as in the above-described embodiment relating to the single cylinder determination. Is confirmed. Then, only when the return to the normal combustion state is confirmed following the confirmation of the misfire state, the occurrence of the misfire is definitely determined. As a result, even in the misfire detection for the two cylinders, erroneous detection due to the vibrational change of the crankshaft angular acceleration and oversight of the occurrence of misfire are prevented.

[0011]

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 carrying out 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. 3, the crank angle sensor 20
Has a rotating member 21 that rotates integrally with the crankshaft 1 of the engine, and a detecting unit 22 that faces the rotating member 21. , Second and third vanes 21a, 21b and 21c are formed.
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 a camshaft (not shown) so as to be rotatable integrally therewith.
While the camshaft rotates twice and the camshaft makes one rotation, a pulse output is generated each time the camshaft takes a specific rotation position corresponding to one cylinder. The controller 10 functions as a main element of the misfire detection device and executes normal various engine controls. A controller 11 for executing various control programs, a read-only memory 12 storing the control programs, and a data A random access memory 13 for temporary storage and the like. The processor 11 receives, via the input circuit 14,
It is connected to various sensors and switches (partially not shown) such as a crank angle sensor 20, a cylinder discriminating sensor 30, an ignition switch 40, an intake air amount sensor, an intake air temperature sensor, and a water temperature sensor. Various actuators including the injection valve 50, various driving circuits for driving the warning lamp 60 and the like (only those corresponding to the elements 50 and 60 are indicated by reference numerals 51 and 61).

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. 4 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 from 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 that the vehicle enters the crankshaft rotation angle region corresponding to the identified cylinder group m (m is 1, 2 or 3) in response to the input of the pulse output from the crank angle sensor 20. Then, the timer for period measurement (not shown) is restarted. The identification cylinder group m includes the cylinder identified in step S1. Crank angle sensor 2
When the next pulse output is input from 0, the processor 11
Determines the departure from the crankshaft rotation angle region corresponding to the identified cylinder group m, stops the timing operation of the period measurement timer, and reads the time measurement result (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 T determined by
m (n). Here, the subscript 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 ° crank angles of the identified cylinder group in the case of the six-cylinder engine, and more generally, (7) in the case of the N cylinder engine.
20 / N) degree cycle between crank angles.

Then, the processor 11 carries out an equation KLm (n) = in order to perform learning for removing a cycle measurement error due to a variation in vane angle intervals in vane manufacturing and mounting.
A correction coefficient KLm (n) related to the identified cylinder group m is calculated according to a · KLm (n−1) + (1−a) · KLm (step S3). Here, the symbol a is a filter constant stored in advance in the read-only memory 12, for example, and takes a value of 0 or more and 1 or less. The 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 random access memory 13, and KLm is expressed by the equation KLm = Tm (n) 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 an 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
Using n, ωn-1 and the correction coefficient KLm (n) calculated in step 3, the formula Dωn = KLm (n) ・ (ωn-ωn-1) ÷ ｛(1 /
2) According to (Tn + Tn-1)｝, the average angular acceleration Dωn of the crankshaft in the 120 ° inter-crank cycle of the current detection cycle is calculated (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 sets the flag FMF
Is determined to be a value "0" indicating that misfire has not been determined in the previous detection cycle or the two-last and previous detection cycles (step S5). If the determination result is affirmative, the first determination is made. Is executed (step S6). As shown in FIG. 5, in the first subroutine, the processor 11 executes step S4 in FIG.
The average angular acceleration Dωn calculated this time is the determination value TH1 (<
0) is first determined (step S61),
If the result of this determination is affirmative, the current average angular acceleration Dω
n is a predetermined change amount ΔT compared to the previous average angular acceleration Dωn-1.
It is further determined whether or not H1 (> 0) or more has decreased (step S62). Then, both the determination results in steps S61 and S62 are affirmative, and the misfire state determination condition that the current value Dωn falls below the determination value TH1 and decreases by a predetermined amount of change ΔTH1 or more compared to the previous value Dωn-1 is satisfied. When determining that the condition is satisfied, the processor 11 sets the flag FMF to:
A value “1” indicating that there is a high probability that a misfire has occurred in the cylinder identified in step S1 (the first misfire detection target cylinder).
(Step S63), the execution of the first subroutine in the current detection cycle is terminated, and when the next pulse output from the crank angle sensor 20 is input, the misfire detection processing of FIG. 4 is restarted.

On the other hand, if the determination result in step S61 or S62 is negative and the above-mentioned misfire state determination condition is not satisfied, the processor 11 sends a drive signal of, for example, L level to the lamp drive circuit 61. Then, the warning lamp 60 is turned off to notify that no misfire has occurred in the cylinder for which misfire has been detected (step S64), and the execution of the first subroutine in the current cycle is ended.

When the processor 11 determines in step S5 that the value of the flag FMF is not "0",
It is further determined whether or not the value of the flag FMF is "1" (step S7). If the determination result is affirmative, the second subroutine is executed (step S8). As shown in FIG. 6, in the second subroutine, the processor 11
Indicates that the average angular acceleration Dωn in the current detection cycle (the detection cycle next to the detection cycle in which the value of the flag FMF is set from “0” to “1”) is the determination value TH2 (≧ TH
It is first determined whether the value exceeds 1) (step S81),
If the result of this determination is affirmative, the current average angular acceleration Dω
n is a predetermined change amount ΔT compared to the previous average angular acceleration Dωn-1.
It is further determined whether or not H2 (ΔTH2 = ΔTH1 or ΔTH2 ≠ ΔTH1) or more has increased (step S82). Then, both the determination results of steps S81 and S82 are affirmative, and the determination condition that the current value Dωn exceeds the determination value TH2 and increases by a predetermined amount of change ΔTH2 or more compared to the previous value Dωn-1 is the second determination condition. When it is determined that the condition has been established for the misfire detection target cylinder and, therefore, the second misfire detection target cylinder has already returned to the normal combustion state, the processor 11
An H level drive signal is sent to the lamp drive circuit 61 to turn on the warning lamp 60 (step S83),
Information indicating that a misfire has occurred only in the first misfire detection target cylinder corresponding to the previous value Dωn-1 is stored in, for example, a predetermined area of the random access memory 13 and the misfire cylinder is stored (step S84). Further, the processor 11 resets the value of the flag FMF to “0” (Step S8)
5), the execution of the second subroutine in the current cycle is ended, and the process waits for re-execution of the main routine of FIG.

On the other hand, if the current value Dωn has not increased by more than the predetermined change amount ΔTH2 as compared with the previous value Dωn-1, step S
When the determination is made at 82, the processor 11 determines in the first subroutine in the previous detection cycle that the misfire state has occurred in the first misfire detection target cylinder by reflecting a decrease in angular acceleration due to some factor other than misfire. It is determined that this provisional judgment result should be cancelled,
The processor 11 sends an L-level drive signal to the lamp drive circuit 61 to turn off the warning lamp 60, reset the value of the flag FMF to “0” (steps S86 and S85), and ends the second subroutine.

If it is determined in step S81 that the current value Dωn does not exceed the determination value TH2, the processor 11 determines whether the current value Dωn related to the second misfire detection target cylinder is present.
ωn is a previous value Dωn related to the first misfire detection target cylinder.
It is further determined whether or not the value has decreased by a predetermined amount of change ΔTH3 (≦ 0) or more compared to −1 (step S87). If the determination result is affirmative and the magnitude relationship as shown in FIG. 8 is established between the value Dωn and the value Dωn−1, the flag FMF
Is set to a value “2” indicating that there is a high probability that a misfire has occurred in both of the two misfire detection target cylinders respectively associated with the value Dωn and the value Dωn−1 (step S88), and the second in the current cycle The execution of the subroutine is ended.

On the other hand, if the current value Dωn has not decreased by a predetermined amount of change ΔTH3 or more compared to the previous value Dωn-1, step S
87, the processor 11 determines the value Dωn and the value Dωn.
Only a magnitude relationship as shown in FIG. 9 is established with ωn-1. Therefore, the decrease in the average angular acceleration occurs only for some reason, such as an angular change in the angular acceleration after a misfire occurs. Judge that there is no. In this case, the processor 11
Determines that no misfire has actually occurred in any of the two misfire detection target cylinders,
The level driving signal is sent out to turn off the warning lamp 60 (step S86), the value of the flag FMF is reset to "0" (step S85), and the second subroutine ends.

If it is determined in step S7 that the value of the flag FMF is not "1", the processor 11 executes a third subroutine (step S9). As shown in FIG. 7, in the third subroutine, the processor 11 performs the current detection cycle (when the value of the flag FMF is “2”).
It is determined whether or not the average angular acceleration Dωn in the detection cycle next to the detection cycle set in (1) has increased by a predetermined amount of change ΔTH4 or more compared to the previous average angular acceleration Dωn-1 (step S91). When the determination result is affirmative and the return to the normal combustion state is confirmed, the processor 1
1 determines that a misfire has occurred in the first and second misfire detection target cylinders, sends an H level drive signal to the lamp drive circuit 61 to turn on the warning lamp 60, and sets the value Dωn−2 Information indicating that a misfire has occurred in the two cylinders respectively corresponding to the previous value Dωn-1 is stored in, for example, a predetermined area of the random access memory 13 and the misfiring cylinder is stored (steps S92 and S93). Further, the value of the flag FMF is reset to "0" (step S94), and the execution of the third subroutine in the current cycle is ended.

On the other hand, if the current value Dωn has not increased by more than the predetermined change amount ΔTH4 as compared with the previous value Dωn-1, step S
When the determination is made at 91, the processor 11
The L level drive signal is sent to 1 to turn off the warning lamp 60 (step S95), the value of the flag FMF is reset to "0" (step S94), and the third subroutine ends.

In the above embodiment, the case where the present invention is applied to a six-cylinder engine has been described. However, the present invention can be applied to various engines such as a four-cylinder engine. In the above-described embodiment, the two-cylinder determination method in which two cylinders to be successively ignited are subjected to misfire determination in the one-time misfire determination process has been described. However, the present invention provides a misfire for only one cylinder at a time. It can be modified to a one-cylinder determination method for performing the determination. In this case, for example, steps S7 and S9 in the main routine shown in FIG. 4 and steps S87 and S9 in FIG.
Step S8 is immediately executed if the determination result in step S5 is negative, and step S86 is immediately executed if the determination result in step S81 is negative.

In the above-described embodiment relating to the two-cylinder determination method, the calculation parameter value Dω corresponding to the first misfire detection target cylinder is used.
n is less than the determination value TH1 and decreases by a predetermined amount of change ΔTH1 or more compared to the parameter value Dωn-1 corresponding to the preceding cylinder (steps S61 and S6 in FIG. 6).
2), the misfire occurrence in the first misfire detection target cylinder is more reliably provisionally determined. However, the misfire occurrence may be provisionally determined only when the value Dωn falls below the determination value TH1.
Alternatively, the value Dωn is smaller than the value Dωn−1 by a predetermined change amount ΔTH1
It is acceptable to use only the decrease as the temporary misfire occurrence provisional judgment condition.
No.

In the above-described embodiment, the parameter value Dωn corresponding to the following cylinder is increased by a predetermined change amount ΔTH4 or more compared to the parameter value Dωn−1 corresponding to the second misfire determination target cylinder (FIG. 7). Step S91), the return to the normal combustion state (misfire occurrence in the first and second misfire detection target cylinders) is determined, but the parameter value corresponding to the following cylinder is determined to be a predetermined determination value. The return determination may be performed when the value exceeds the threshold. In this case, the magnitude of the value Dωn is compared with the determination value for the return determination in step S91, and one of steps S92 and S95 in FIG. 7 may be executed according to the comparison result. Alternatively, in order to more reliably perform the return determination to the normal combustion state, and hence the misfire determination, the return determination is made based on the fact that the value Dωn exceeds the determination value for the return determination and increases by a change amount ΔTH4 or more compared to the value Dωn−1. It may be performed.

In connection with this modified example, in the above embodiment, the parameter value Dωn corresponding to the second cylinder for detecting misfire exceeds the determination value TH2 and the parameter value corresponding to the first cylinder for detecting misfire. When the amount of change has increased by the predetermined change amount ΔTH2 or more compared to the value Dωn-1, the return to the normal combustion state is more reliably determined, and the occurrence of misfire only in the first misfire detection target cylinder is definitely determined. (Steps S81 and S82 in FIG. 6). However, only one of steps S81 and S82 may be executed in order to easily determine the return to the normal combustion state. That is,
In a case where step S82 is omitted and only step S81 is performed, first, the determination value TH2 is set to a value (T
After setting H2> TH1), if the determination result in step S81 is affirmative, the process may proceed to step S83. Step S81 is omitted and step S81 is omitted.
When only 82 is executed, step S87 is first executed in the second subroutine of FIG. 6, and if the result of the determination is affirmative, the process proceeds to step S88, while if the result of the determination is negative, the process proceeds to step S82. Further, if the determination result in the step S82 is affirmative, the process shifts to the step S83, while if the determination result is negative, a step S86 is performed.
The control procedure may be configured to shift to.

Further, the various judgment values and the predetermined change amounts in the above embodiment are illustrative and can be set variously.
It can be variably set according to the engine operation area and load condition. Further, in the above-described embodiment, in the misfire detection process (FIG. 4), the correction coefficient is calculated to eliminate 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.

[0032]

As described above, the parameter value representing the crankshaft angular acceleration corresponding to each cylinder of the internal combustion engine is repeatedly calculated, and the presence or absence of a misfire occurrence in the misfire detection target cylinder is detected based on the calculated parameter value. In the misfire detection method according to the crankshaft rotation fluctuation, the misfire detection method of the present invention, the calculation parameter value corresponding to the misfire detection target cylinder,
With less than the first determination value, the called decreased compared to the calculated parameter value corresponding to the preceding cylinders to be ignited operation immediately before the ignition operation to be performed by the misfire detection target cylinder first predetermined change amount or more 1 It is determined whether or not the determination condition is satisfied, and the calculated parameter value corresponding to the succeeding cylinder to be ignited immediately after the ignition operation to be performed in the misfire detection target cylinder exceeds the second determination value, Alternatively, it is determined whether or not a second determination condition that the value has increased by a second predetermined change amount or more compared to a calculated parameter value corresponding to the misfire detection target cylinder is satisfied, and the first and second determination conditions are determined. When both are established, the misfire occurrence in the misfire detection target cylinder is detected, so even if the angular acceleration of the crankshaft increases or decreases due to the occurrence of the misfire state once Accurately check for misfires It can, moreover, does not require special hardware for this.

Further, the misfire detection method according to another aspect of the present invention provides a method for calculating a misfire detection parameter corresponding to a first misfire detection target cylinder to be ignited first among two misfire detection target cylinders to be successively ignited. The value is smaller than the first determination value, or the first predetermined value is compared with the calculated parameter value corresponding to the preceding cylinder to be ignited immediately before the ignition operation to be performed in the first misfire detection target cylinder. It is determined whether or not a first determination condition that the amount of change has decreased by more than the amount of change is satisfied, and the calculated parameter value corresponding to the second cylinder targeted for misfire detection is determined as the calculated parameter value corresponding to the first cylinder targeted for misfire detection. It is determined whether or not a second determination condition that the amount has decreased by a second predetermined change amount or more is satisfied, and the ignition operation is performed immediately after the ignition operation to be performed in the second misfire detection target cylinder. Calculation parameters corresponding to the line cylinder A third determination condition that the data value exceeds the second determination value or increases by a third predetermined change amount or more compared to the calculated parameter value corresponding to the second misfire detection target cylinder is satisfied It is determined whether or not to perform
Further, since the occurrence of misfire in the first and second misfire detection target cylinders is detected when all of the third determination conditions are satisfied, the same effect as in the case of the above-described single cylinder determination is obtained. Play. In addition, it is possible to detect a two-cylinder continuous misfire that cannot be detected by a misfire detection method (Japanese Patent Application No. 4-149432, filed by the same applicant as the present application) designed to prevent erroneous detection due to angular acceleration vibration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an oscillating change in crankshaft angular acceleration due to occurrence of a misfire.

FIG. 2 is a schematic block diagram showing an apparatus for implementing a misfire detection method according to one embodiment of the present invention.

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

FIG. 4 is a flowchart showing a misfire detection process executed by the controller of FIG. 2;

FIG. 5 is a flowchart showing details of a first subroutine shown in FIG. 4;

FIG. 6 is a flowchart showing a second subroutine shown in FIG. 4 in detail.

FIG. 7 is a flowchart showing details of a third subroutine shown in FIG. 4;

FIG. 8 is a graph exemplifying a state in which the average angular acceleration Dω corresponding to the second misfire detection target cylinder is smaller than that corresponding to the first misfire detection target cylinder.

FIG. 9 is a graph illustrating a state in which the average angular acceleration Dω corresponding to the second misfire detection target cylinder is larger than that corresponding to the first misfire detection target cylinder.

[Explanation of symbols]

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

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Yasuhisa Yoshida 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-4-311649 (JP, A) Hei 6-207553 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 45/00

Claims (3)

(57) [Claims] 1. A crankshaft rotation fluctuation for repeatedly calculating a parameter value representing a crankshaft angular acceleration corresponding to each cylinder of an internal combustion engine and detecting whether or not a misfire has occurred in a misfire detection target cylinder based on the calculated parameter value. in the misfire detection method according to the calculated parameter value corresponding to the misfire detection target cylinder, with less than a first determination value, corresponding to the preceding cylinders to be ignited operation immediately before the ignition operation to be performed by the misfire detection target cylinder It is determined whether or not a first determination condition that the amount of change has decreased by a first predetermined amount or more compared with the calculated parameter value is satisfied, and the ignition operation is performed immediately after the ignition operation to be performed in the misfire detection target cylinder. The calculated parameter value corresponding to the power-up following cylinder exceeds the second determination value, or the calculated parameter value corresponding to the misfire detection target cylinder is a second predetermined value. It is determined whether or not a second determination condition that the amount of change has increased by an amount equal to or greater than a change amount is satisfied. When both the first and second determination conditions are satisfied, a misfire occurrence in the misfire detection target cylinder is detected. A method for detecting misfire due to crankshaft rotation fluctuations. 2. A crankshaft rotation fluctuation for repeatedly calculating a parameter value representing a crankshaft angular acceleration corresponding to each cylinder of an internal combustion engine, and detecting whether or not a misfire has occurred in a misfire detection target cylinder based on the calculated parameter value. The calculated parameter value corresponding to the first misfire detection target cylinder to be ignited first among the two misfire detection target cylinders to be successively ignited is lower than the first determination value. Or a first predetermined change amount that has decreased by at least a first predetermined change amount compared with a calculated parameter value corresponding to a preceding cylinder to be ignited immediately before an ignition operation to be performed in the first misfire detection target cylinder. It is determined whether or not the determination condition is satisfied, and the calculated parameter value corresponding to the second cylinder targeted for misfire detection is compared with the calculated parameter value corresponding to the first cylinder targeted for misfire detection. It is determined whether or not a second determination condition that it has decreased by more than the predetermined change amount of 2 is satisfied, and immediately after the ignition operation to be performed in the second misfire detection target cylinder, A third case in which the corresponding calculated parameter value exceeds the second determination value or has increased by a third predetermined change amount or more compared to the calculated parameter value corresponding to the second misfire detection target cylinder. Determining whether or not a determination condition is satisfied, and detecting occurrence of a misfire in the first and second misfire detection target cylinders when all of the first, second, and third determination conditions are satisfied; A method for detecting misfire due to fluctuations in crankshaft rotation. 3. A calculation parameter value corresponding to the first misfire detection target cylinder is lower than the first determination value, and the first predetermined change amount is smaller than a calculation parameter value corresponding to the preceding cylinder. 3. The method according to claim 2 , wherein the first determination condition is determined to be satisfied when the value decreases.
Misfire detection method due to crankshaft rotation fluctuation.