JP2004218605A - Misfire sensing device of internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a misfire sensing device for an internal-combustion engine capable of preparing a map for calculation of the misfire judging value with a simple adaptation, decreasing the man-hours for adaptation, and enhancing the interpolation accuracy. <P>SOLUTION: The rotating speed change amount Δωn in the specified period is calculated on the basis of the mean rotating speed ωn as the inverse number of the time T120n required for the crank shaft to make 120[°CA] rotation (Step S105). The obtained change amount Δωn is compared with the misfire judging value REF for judging misfire and a judgement is made if misfire exists (Step S109). Because the value REF and the period T as the time in which the crank shaft of the internal-combustion engine makes one turn are approximately proportional and in the linear relation, the map for calculation of the misfire judging value REF can be obtained with simple adaptation. Thereby the man-hours for adaptation at the time of preparing the map can be decreased, and the interpolation accuracy when the misfire judging value is calculated using the map can be enhanced. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a misfire detection device for an internal combustion engine that detects a misfire occurring in the internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as prior art documents related to a misfire detection device for an internal combustion engine, those disclosed in JP-A-3-164553 and JP-A-6-229311 are known. Among them, Japanese Patent Application Laid-Open No. 3-164553 discloses that it is not necessary to change the misfire determination value (slice level) according to the rotation speed of the internal combustion engine (engine rotation speed). ), While saving ROM capacity. Also, Japanese Patent Application Laid-Open No. Hei 6-229313 discloses that the influence of a detection error caused by an error in the configuration of a rotation speed sensor (crank angle sensor) for detecting a crankshaft rotation fluctuation is removed to accurately determine whether a misfire has occurred. Discloses a detection technique.
[0003]
Here, the negative angular acceleration (time change of the rotational speed) at the time of misfire of the internal combustion engine is proportional to the output torque of the internal combustion engine at the time of combustion, but when the output torque is the same, the negative angular acceleration depends on the angular speed (rotational speed). Constant. However, in the calculation of the rotational speed fluctuation amount used for misfire detection, for example, the rotational speed is synchronized with the phase of the crankshaft rotation, such as obtaining the difference between the rotational speeds of two cylinders having consecutive combustion strokes in the same phase. Speed is being detected. Therefore, the time interval for calculating the rotation speed fluctuation amount is inversely proportional to the rotation speed, and the rotation speed fluctuation amount at the time of misfire is inversely proportional to the rotation speed.
[0004]
Further, the misfire determination value is set in advance to a value that takes into account the variation in the rotational speed fluctuation amount at the time of misfire. In view of the above, in the conventional misfire detection, in order to match the above-described characteristics, a misfire determination value is determined by using a map in which a physical quantity related to an intake air amount having a large correlation with an output torque in a combustion stroke of the internal combustion engine and a rotation speed of the internal combustion engine are parameters. It is set in. With this mapping, in addition to the main correction based on the difference in the rotation speed due to the difference in the rotation speed and the output torque of the internal combustion engine, the influence of the correlation between the intake air amount of the internal combustion engine and the correlation between the output torque and the rotation speed, Minor corrections such as the effects of friction are also made.
[Patent Document 1] JP-A-3-164553 (pages 1 to 3)
[Patent Document 2] Japanese Patent Application Laid-Open No. 6-229311 (pages 2 to 3)
[0005]
[Problems to be solved by the invention]
As described above, conventionally, the rotation speed of the internal combustion engine is used as one of the parameters in the map for calculating the misfire determination value. This rotation speed is detected at a timing synchronized with the phase of the crankshaft rotation. With the same intake air amount, the rotation speed fluctuation amount at the time of misfiring changes in a curve substantially in inverse proportion to the rotation speed. For this reason, as shown in FIG. 6, when the engine speed NE [rpm] is used as a parameter in the misfire detection as a parameter, the engine speed NE [rpm] and the misfire determination value REF [rpm] are used. Had to be set in a curve so that the relationship was almost inversely proportional.
[0006]
In order to improve the interpolation accuracy in the map having such a curved characteristic, it is necessary to increase the number of map points, so that the adaptation man-hour is excessively required and the storage capacity is increased. Further, since the misfire determination value REF between map points is calculated by linear interpolation, it is impossible to improve the calculation accuracy of the misfire determination value REF.
[0007]
Therefore, the present invention has been made to solve such a problem, and a map for calculating a misfire determination value can be obtained by a simple adaptation, and as a result, the adaptation man-hour can be reduced and the interpolation accuracy can be improved. It is an object to provide a misfire detection device for an internal combustion engine.
[0008]
[Means for Solving the Problems]
According to the internal combustion engine misfire detection device of the first aspect, the misfire determination value is stored in the map in advance as a value corresponding to the rotation cycle, and the internal combustion engine is calculated by the misfire determination value and the rotational speed fluctuation amount calculating means. The misfire detecting means compares the amount of change in the rotational speed during a predetermined period based on the rotational speed of the engine with the presence of a misfire in the internal combustion engine. Here, the misfire determination value and the rotation cycle are substantially proportional and linear, so that a map for calculating the misfire determination value can be obtained with a simple adaptation. As a result, the man-hours required for creating a map are reduced, and the accuracy of interpolation when calculating a misfire determination value using the map is improved.
[0009]
The rotational speed fluctuation amount calculating means in the misfire detection device for an internal combustion engine according to claim 2 calculates a rotational speed difference between a rotational speed of a current combustion stroke in a continuous combustion stroke and a rotational speed of a previous combustion stroke. Using the difference between the rotation speeds and the difference between the rotation speeds before one rotation of the crankshaft, the rotation speed fluctuation amount for a predetermined period is suitably calculated. As a result, the current rotational speed difference is compared with the rotational speed difference before one rotation of the crankshaft, and thus is calculated as a value that is not affected by errors due to component tolerances or the like when detecting the rotational speed. Therefore, the presence or absence of a misfire in the internal combustion engine is accurately determined by comparing the rotation speed fluctuation amount during the predetermined period with the misfire determination value.
[0010]
In the misfire detection device for an internal combustion engine according to the third aspect, the rotational speed of the current combustion stroke and the rotational speed of the previous combustion stroke are set to values in the same phase in the respective combustion strokes. The rotation speed fluctuation amount is more preferably calculated.
[0011]
In the misfire detection device for an internal combustion engine according to the fourth aspect, the rotation period is calculated based on the latest information of the period during which the crankshaft of the internal combustion engine makes one rotation, so that the average rotation period in the rotation speed fluctuation amount calculation period is reduced. It is possible to obtain a favorable result without being affected by a detection error for each crank angle of the crankshaft.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described based on examples.
[0013]
FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which a misfire detection device for an internal combustion engine according to one embodiment of the present invention is applied, and peripheral devices thereof.
[0014]
In FIG. 1, reference numeral 10 denotes an internal combustion engine composed of four cylinders of six cylinders (cylinders # 1 to # 6), and reference numeral 11 denotes an intake passage for supplying intake air introduced from an air cleaner 12 to the internal combustion engine 10 side. Reference numeral 13 denotes an intake air amount sensor such as an air flow meter for detecting an intake air amount GN [g / rev] introduced into the intake passage 11.
[0015]
Reference numeral 21 denotes a rotation speed sensor which is provided on the crankshaft 16 of the internal combustion engine 10 and outputs a signal at every predetermined crank angle to determine an engine rotation speed NE [rpm]. Is a reference position sensor for detecting a reference position G for each compression TDC (Top Dead Center: Top Dead Center) at which the piston 17 of the # 1 cylinder rises most, for example. Reference numeral 24 denotes a water temperature sensor that is disposed in the cooling water passage of the internal combustion engine 10 and detects a cooling water temperature THW [° C.].
[0016]
Reference numeral 30 denotes an intake air amount GN from the intake air amount sensor 13, an engine rotational speed NE from the rotational speed sensor 21, a reference position G from the reference position sensor 23, a cooling water temperature THW from the water temperature sensor 24, and various other sensor signals. ECU (Electronic Control Unit: electronic control unit) that inputs and calculates optimal control amounts in the fuel system and the ignition system, and outputs control signals for accurately controlling the injector (fuel injection valve) 26, the igniter 27, and the like. It is.
[0017]
The ECU 30 includes a CPU 31 serving as a central processing unit for executing various known arithmetic processing, a ROM 32 storing control programs and control maps, a RAM 33 storing various data and the like, a B / U (backup) RAM 34, an input / output circuit 35, It is configured as a logical operation circuit including a bus line 36 connecting them. Reference numeral 29 denotes a warning lamp for notifying a driver or the like of the occurrence of a misfire when the ECU 30 determines that a misfire has occurred.
[0018]
Next, referring to FIG. 3 based on a flowchart of FIG. 2 showing a processing procedure for determining whether or not there is a misfire in the CPU 31 in the ECU 30 used in the misfire detection apparatus for the internal combustion engine according to one embodiment of the present invention. Will be explained. Here, FIG. 3 determines whether there is a misfire during the operation of the internal combustion engine 10 using the intake air amount GN [g / rev] and a cycle (crankshaft rotation cycle) T [ms: millisecond] described in FIG. 2 as parameters. Is a map for calculating a misfire determination value REF. The misfire determination routine is repeatedly executed by the CPU 31 at predetermined crank angle intervals, for example, every 30 [° CA (Crank Angle: crank angle)].
[0019]
In FIG. 2, first, in step S101, a current time T30i required for the crankshaft 16 to rotate by 30 [° CA] is calculated from a difference between the previous interrupt time and the current interrupt time. Next, the process proceeds to step S102, and it is determined whether the current interrupt timing is the compression TDC in any of the cylinders # 1 to # 6. If the determination condition in step S102 is not satisfied, that is, if the current interrupt timing is not the compression TDC, the routine ends without performing any operation.
[0020]
On the other hand, when the determination condition of step S102 is satisfied, that is, when the current interrupt timing is the compression TDC in any one of the cylinders # 1 to # 6, the process proceeds to step S103 and is calculated in step S101. The data of the current time T30i and the times T30i-1, T30i-2, and T30i-3 calculated at the time of the previous execution, the last two executions, and the three previous executions, respectively, are accumulated, and the crankshaft 16 is rotated by 120 °. CA] The time T120n required for rotation is calculated.
[0021]
Next, the process proceeds to step S104, and the current average rotational speed ωn is calculated by the reciprocal of the time T120n required for the crankshaft 16 of the internal combustion engine 10 to rotate 120 [° CA] calculated in step S103. . Next, the process proceeds to step S105, where the current rotational speed fluctuation amount Δωn is calculated by the following equation (1). Here, [omega] n-1 is the average rotation speed calculated at the previous execution, [omega] n-3 is the average rotation speed calculated three times before, and [omega] n-4 is the average rotation speed calculated at the execution four times before. Further, (ωn−1−ωn) is the latest rotational speed difference in the cylinder where the combustion stroke is continuous, and (ωn−4−ωn−3) is the rotation before 360 [° CA] in the cylinder where the combustion stroke is continuous. It is a speed difference. This makes it possible to calculate the rotation speed fluctuation amount for the same tooth portion of the rotation speed sensor 21, and eliminate an error due to component tolerance or the like in the tooth portion of the rotation speed sensor 21.
[0022]
(Equation 1)
Δωn ← (ωn−1−ωn) − (ωn−4−ωn−3) (1)
[0023]
In the above equation (1), the latest rotational speed difference (ωn−1−ωn) and the rotational speed difference (ωn−4−ωn−3) before 360 [° CA] are calculated simultaneously. If the latest rotational speed difference (ωn−1−ωn) is stored in the RAM 33 as the rotational speed difference (ωn−4−ωn−3) 360 [° CA] before the next calculation, this 360 [ The rotational speed difference (ωn−4−ωn−3) before (° CA) is read from the RAM 33 to calculate the rotational speed difference (ωn−4−ωn−3) before 360 [° CA]. The rotation speed fluctuation amount Δωn can be calculated without performing the above operation.
[0024]
Next, the process proceeds to step S106, where the intake air amount GN [g / rev: rotation per gram] is read from the intake air amount sensor 13. Next, the process proceeds to step S107, and a cycle (crankshaft rotation cycle) T [ms] as a time required for the crankshaft 16 of the internal combustion engine 10 to make one rotation is calculated by the following equation (2).
[0025]
(Equation 2)
T ← T120n + T120n-1 + T120n-2 (2)
[0026]
Next, the process proceeds to step S108, and based on the map shown in FIG. 3 using the intake air amount GN [g / rev] read in step S106 and the cycle T [ms] calculated in step S107 as parameters, the presence or absence of misfire Is determined to determine the misfire. Note that the misfire determination value REF for the intermediate value of each parameter in FIG. 3 is obtained by an interpolation calculation.
[0027]
Next, the process proceeds to step S109, and it is determined whether the current rotational speed fluctuation amount Δωn calculated in step S105 exceeds the misfire determination value REF calculated in step S108. If the determination condition of step S109 is satisfied, that is, if the current rotation speed fluctuation amount Δωn exceeds the misfire determination value REF and is large, the process proceeds to step S110, and the misfire determination flag XMF is set to “1” indicating that there is misfire. On the other hand, when the determination condition of step S109 is not satisfied, that is, when the current rotational speed variation Δωn is smaller than or equal to the misfire determination value REF, the process proceeds to step S111, and the misfire determination flag XMF is set to “0” indicating no misfire. Is done.
[0028]
After the processing in step S110 or step S111, the process proceeds to step S112, in which the current average rotational speed ωn is the previous average rotational speed ωn-1, the previous average rotational speed ωn-1 is the previous average rotational speed ωn-2, and the previous rotational speed is the previous one. The average rotation speed ωn-3 of the previous three rotations is the average rotation speed ωn-3 of the previous rotation, the average rotation speed ωn-3 of the third rotation is the average rotation speed ωn-4 of the previous rotation four times, and the current rotation speed fluctuation Δωn is , The previous rotation speed variation Δωn−1 is the previous rotation speed variation Δωn−2, the current time T120n is the previous time T120n−1, and the previous time T120n−1 is the previous two times. It is updated at time T120n-2, respectively, and this routine ends.
[0029]
In the map of FIG. 3 used in the above-mentioned misfire determination routine, the misfire determination value REF is calculated using the intake air amount GN [g / rev] and the cycle T [ms] as parameters. Here, when the intake air amount GN [g / rev] is constant, as shown in FIG. 4, the relationship between the cycle T [ms] and the misfire determination value REF [rpm] is linearly adjusted so as to be substantially proportional. Can be set. Next, the reason will be described.
[0030]
Now, assuming that the vehicle is traveling at a constant speed, the output torque Te of the internal combustion engine 10 and the load torque W at that time are balanced, and when the moment of inertia is I, the relationship is as follows: ).
[0031]
[Equation 3]
Te-W = I * (dω / dt) (3)
[0032]
Here, assuming that the current average rotational speed ωn calculation cylinder misfires, the output torque Te becomes “0”, and the previous average rotational speed ωn−1 calculation cylinder does not misfire, the above equation (3) becomes It is represented by (4).
[0033]
(Equation 4)
−W = I * (dω / dt) ≒ I * (ωn−ωn−1) / T120n (4)
[0034]
Further, if it is assumed that the cylinder for calculating the average rotation speed ωn-3 three times before and the cylinder for calculating the average rotation speed ωn-4 four times before have not misfired, the above equation (3) is expressed by the following equation (5). It is.
[0035]
(Equation 5)
Te−W = I * (dω / dt) ≒ I * (ωn−3−ωn−4) / T120n (5)
[0036]
When the above equation (4) is subtracted from the above equation (5), the following equation (6) is obtained.
[0037]
(Equation 6)
Te {I * {(ωn−1−ωn) − (ωn−4−ωn−3)} / T120n (6)
[0038]
Therefore, the following equation (7) is substantially satisfied.
[0039]
(Equation 7)
Te * T120n {(ωn-1 -ωn)-(ωn-4 -ωn-3)} (7)
[0040]
Note that the absolute amount of T120n is sufficiently large compared to the amount of fluctuation when there is a misfire, and for the sake of simplicity, both the presence and absence of misfire are constant. In addition, since the intake air amount GN∝Te is substantially satisfied, the following equation (8) is obtained.
[0041]
(Equation 8)
GN * T {GN * T120n {(ωn-1-ωn)-(ωn-4-ωn-3)} (8)
[0042]
As a result, the misfire determination value REF preset to a value that takes into account the variation with respect to the rotational speed fluctuation amount {(ωn−1−ωn) − (ωn−4−ωn−3)} when there is a misfire. Is proportional to the period T. Therefore, by using the cycle T as a parameter in the map for obtaining the misfire determination value REF, these relationships can be made substantially linear.
[0043]
Next, a description will be given based on a flowchart of FIG. 5 showing a processing procedure of abnormality diagnosis in the CPU 31 in the ECU 30 used in the misfire detection device for the internal combustion engine according to one embodiment of the embodiment of the present invention. This abnormality diagnosis routine is repeatedly executed by the CPU 31 at predetermined time intervals.
[0044]
In FIG. 5, in step S201, the states of various abnormality determination flags including the misfire determination flag XMF in the above-described misfire presence / absence determination routine are read. Next, the process proceeds to step S202, where the occurrence of an abnormality is determined based on the state of the various abnormality determination flags read in step S201. When the determination condition of step S202 is not satisfied, that is, when all the states of the various abnormality determination flags are “0”, it is determined that there is no abnormality, and the routine ends.
[0045]
On the other hand, when the determination condition of step S202 is satisfied, that is, when any one of the states of the various abnormality determination flags is “1”, the process proceeds to step S203. In step S203, for example, when the misfire determination flag XMF is set to “1” as the state of the various abnormality determination flags, protection of a catalyst (not shown) and the concentration of HC (hydrocarbon) in exhaust gas are performed. In order to prevent an increase, a well-known fail-safe corresponding to abnormality detection such as stopping fuel supply to a cylinder determined to have a misfire or turning on a warning 29 for notifying a driver or the like of the occurrence of a misfire. The process is executed, and this routine ends.
[0046]
As described above, the misfire detection device for an internal combustion engine according to the present embodiment is the reciprocal of the time required for the crankshaft 16 of the internal combustion engine 10 to rotate by 120 ° C. as a predetermined period detected by the rotational speed sensor 21. A rotational speed fluctuation calculating means, which is achieved by the ECU 30 for calculating a rotational speed fluctuation Δωn for a predetermined period based on the average rotational speed ωn, and a rotational speed fluctuation for a predetermined period calculated by the rotation speed fluctuation calculating means A misfire detecting means which is achieved by the ECU 30 for detecting misfire of the internal combustion engine 10 based on Δωn and a misfire decision value REF for judging misfire, wherein the misfire decision value REF is a cycle (crankshaft rotation cycle). It is stored in the map in advance as a value corresponding to T.
[0047]
That is, the misfire determination value REF is mapped in advance with the cycle T as one parameter and stored in the ROM 32 (see FIG. 3), and the rotational speed fluctuation amount Δωn for a predetermined period is compared with the misfire determination value REF. It is determined whether a misfire has occurred in the internal combustion engine 10. Here, since the misfire determination value REF and the cycle T are substantially proportional to each other and are linear, a map for calculating the misfire determination value can be obtained by simple adaptation. As a result, the man-hours required for creating a map can be reduced, and the accuracy of interpolation when calculating a misfire determination value using this map can be improved.
[0048]
In addition, the rotation speed fluctuation amount calculation means achieved by the ECU 30 of the misfire detection device for an internal combustion engine according to the present embodiment calculates a rotation speed difference (ωn-1-ωn) based on the rotation speed of the current combustion stroke among the continuous combustion strokes. ) And the rotation speed difference (ωn−4−ωn−3) before 360 [° CA], to calculate the rotation speed fluctuation amount Δωn for a predetermined period. That is, according to the rotation speed difference (ωn−1−ωn) of the current combustion stroke in the continuous combustion stroke and the rotation speed difference (ωn−4−ωn−3) 360 [° CA] before, the predetermined period is determined. The rotation speed variation Δωn which is not affected by errors due to component tolerances and the like in the tooth portion of the rotation speed sensor 21 is preferably calculated, and compared with the misfire determination value REF using the rotation speed variation Δωn. Thus, the presence or absence of misfire in the internal combustion engine 10 can be accurately determined.
[0049]
In the misfire detection device for an internal combustion engine according to the present embodiment, the rotation speed in the current combustion stroke and the rotation speed in the previous combustion stroke have the same phase in each combustion stroke. In other words, since the rotation speed of the combustion stroke in the same phase is used, it is possible to calculate an accurate rotation speed fluctuation amount Δωn without an error due to a component tolerance or the like in a tooth portion of the rotation speed sensor 21. In such a case, the rotation speed fluctuation amount Δωn can be more suitably calculated.
[0050]
Furthermore, the misfire detection device for an internal combustion engine according to the present embodiment calculates the cycle T based on the latest measured value during a period in which the crankshaft 16 of the internal combustion engine 10 makes one revolution. As described above, the cycle T calculated based on the latest information of the period during which the crankshaft 16 of the internal combustion engine 10 makes one rotation is defined as an average rotation period during the rotation speed fluctuation amount calculation period, for each crank angle of the crankshaft 16. Can be suitably obtained without being affected by the detection error.
[0051]
By the way, in the above embodiment, the internal combustion engine 10 has been described assuming a 4-cycle, 6-cylinder (# 1 cylinder to # 6 cylinder). However, the present invention is not limited to this. In short, when calculating the rotation speed fluctuation amount, the rotation speed in the same phase in the continuous combustion stroke may be used.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an internal combustion engine to which a misfire detection device for an internal combustion engine according to an embodiment of the present invention is applied, and peripheral devices thereof.
FIG. 2 is a flowchart showing a processing procedure of a misfire presence / absence determination in a CPU in an ECU used in a misfire detection apparatus for an internal combustion engine according to one embodiment of the present invention.
FIG. 3 is a map for calculating a misfire determination value for determining the presence or absence of a misfire during operation of the internal combustion engine using the intake air amount and the cycle as parameters in FIG. 2;
FIG. 4 is a characteristic diagram showing a relationship between a cycle and a misfire determination value used in a misfire detection device for an internal combustion engine according to one example of an embodiment of the present invention.
FIG. 5 is a flowchart showing a processing procedure of abnormality diagnosis in a CPU in an ECU used in a misfire detection device for an internal combustion engine according to one example of an embodiment of the present invention.
FIG. 6 is a characteristic diagram showing a relationship between an engine speed and a misfire determination value used in a conventional misfire detection device for an internal combustion engine.
[Explanation of symbols]
Reference Signs List 10 internal combustion engine 16 crankshaft 21 rotation speed sensor 30 ECU (electronic control unit)
32 ROM

Claims (4)

Rotation speed fluctuation amount calculating means for calculating a rotation speed fluctuation amount for a predetermined period based on the rotation speed of the internal combustion engine,
A misfire detection unit that detects misfire of the internal combustion engine based on the rotation speed variation amount of the predetermined period calculated by the rotation speed variation amount calculation unit and a misfire determination value for determining misfire,
A misfire detection device for an internal combustion engine, wherein the misfire determination value is stored in a map in advance as a value corresponding to a rotation cycle. The rotation speed fluctuation amount calculating means calculates a rotation speed difference between a rotation speed of a current combustion stroke and a rotation speed of a previous combustion stroke in a continuous combustion stroke, and calculates a difference between the rotation speed difference and one rotation of a crankshaft. 2. The misfire detection device for an internal combustion engine according to claim 1, wherein the rotational speed fluctuation amount for the predetermined period is calculated based on the rotational speed difference similarly calculated. The misfire detection device for an internal combustion engine according to claim 2, wherein the rotation speed of the current combustion stroke and the rotation speed of the previous combustion stroke have the same phase in each combustion stroke. The misfire detection of the internal combustion engine according to any one of claims 1 to 3, wherein the rotation cycle is calculated based on a latest measured value during a period when the crankshaft of the internal combustion engine makes one revolution. apparatus.

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