JP3922468B2 - Misfire detection device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a misfire detection apparatus for an internal combustion engine that detects a misfire occurring in the internal combustion engine from the rotational state of the internal combustion engine.
[0002]
[Prior art]
In general, when a misfire occurs in a combustion chamber in a cylinder of an internal combustion engine (hereinafter referred to as an “engine”), the rotational speed of the explosion stroke is reduced. Therefore, as shown in JP-A-61-258955, the explosion of each cylinder There is a type in which a rotational speed fluctuation amount is calculated for each stroke, and the rotational speed fluctuation amount is compared with a predetermined misfire determination value to determine the presence or absence of misfire in each cylinder.
[0003]
However, as shown in FIG. 7, the rotational speed fluctuation amount ΔT for each explosion stroke of each cylinder varies among the cylinders. If a uniform misfire determination value is set for all cylinders, misfire cannot be detected at the time of misfire. There is a risk of misjudgment that misfire has occurred during normal combustion.
[0004]
In order to solve this problem, as shown in JP-A-5-195858, the misfire determination value is corrected with a correction coefficient set in advance for each cylinder in accordance with the degree of variation in the combustion state of each cylinder. In some cases, the misfire determination value corrected for each cylinder is compared with the rotation speed fluctuation amount ΔT for each explosion stroke of each cylinder to determine the presence or absence of misfire in each cylinder.
[0005]
[Problems to be solved by the invention]
In the above-described conventional configuration, the correction coefficient is set for each cylinder according to the degree of variation in the combustion state of each cylinder. However, the degree of variation in the combustion state of each cylinder varies between engines, and over time. Since variations also occur due to changes, it is difficult to set an appropriate correction coefficient for all engines in advance, and it is impossible to properly deal with secular changes. Therefore, in the method of correcting the misfire determination value with the correction coefficient set in advance for each cylinder, there is a possibility of erroneous determination although it is small, and further improvement in misfire determination accuracy has been desired.
[0006]
The present invention has been made in view of such circumstances, and an object thereof is to provide a misfire detection apparatus for an internal combustion engine that can improve misfire determination accuracy.
[0007]
[Means for Solving the Problems]
  In order to achieve the above object, a misfire detection device for an internal combustion engine according to claim 1 of the present invention has a predetermined response according to the rotation of the internal combustion engine (hereinafter referred to as “engine”), as illustrated in FIG. A rotation signal is output from the rotation signal output means 1 for each rotation angle, and a rotation speed fluctuation amount for each explosion stroke of each cylinder of the engine is calculated by the rotation speed fluctuation amount calculation means 2 based on this rotation signal. At this time, the cylinder-specific correction value calculation means 3 receives the rotation signal from the rotation signal output means 1.Signals during which no misfire occurs immediately after ignitionBased on the above, the rotational speed deviation between the cylinders is learned, and a correction value corresponding to the rotational speed deviation is calculated for each cylinder. The rotational speed fluctuation amount correcting means 4 corrects the rotational speed fluctuation amount for each explosion stroke of each cylinder calculated by the rotational speed fluctuation amount calculating means 2 with the correction value calculated by the cylinder specific correction value calculating means 3. The misfire determination means 6 compares the corrected rotational speed fluctuation amount for each explosion stroke of each cylinder with a predetermined misfire determination value stored in the misfire determination value storage means 5 to determine whether or not each cylinder has misfired. To do.
[0008]
  In this case, instead of correcting the misfire determination value as in the prior art, the rotational speed variation between the cylinders is corrected by correcting the rotational speed fluctuation amount by the correction value obtained by learning the rotational speed deviation between the cylinders. Because it absorbs (corrects) deviations, it can appropriately handle variations between engines and changes over time.Moreover, since the learning timing of the rotational speed deviation between each cylinder is set to a period in which the influence of misfire immediately after ignition of each cylinder does not appear, the rotational speed deviation can be learned without being affected by misfiring. Accuracy can be improved.
[0009]
Further, in claim 2, the cylinder specific correction value calculation means 3 learns the rotational speed deviation from the difference between the rotational speed immediately after ignition of each cylinder and the rotational speed before one rotation (before 360 ° C. A). As shown in FIG. 5, immediately after the ignition of each cylinder, the rotational speed is not affected even in the case of misfire, and the rotational speed is the same as that in the normal combustion at the time of misfire. If the rotational speed deviation is learned from the difference from the previous rotational speed, the rotational speed deviation can be learned without being affected by misfire, and learning accuracy is improved.
[0010]
Further, in claim 3, the cylinder specific correction value calculation means 3 uses the correction value calculated for the specific cylinder as the correction value for the cylinder whose ignition timing is shifted by one rotation (360 ° C. A) from the specific cylinder. . That is, the absolute value of the relationship between the correction value (rotational speed deviation) for a specific cylinder and the correction value (rotational speed deviation) for a cylinder whose ignition timing is shifted by one revolution (360 ° C. A) is approximately equal to ± Therefore, if the correction value calculated for a specific cylinder is also used for a cylinder shifted by one revolution (360 ° C. A), the correction value calculation process may be performed for half of the cylinders. , The calculation load can be reduced.
[0011]
Further, in claim 4, the cylinder specific correction value calculating means 3 performs the correction value smoothing process. Thereby, an excessive change of the correction value is moderately suppressed, and a reliable correction value is obtained.
[0012]
Further, in claim 5, the cylinder specific correction value calculating means 3 obtains a correction value by averaging the learned absolute value of the rotational speed deviation for the cylinders whose ignition timing is shifted by one revolution. Also in this case, an excessive change in the correction value is moderately suppressed, and a reliable correction value is required.
[0013]
Further, in claim 6, as exemplified in FIG. 1B, the cylinder specific correction value calculation means 3 learns a correction value for each engine load output from the engine load output means 7, and the learning result is obtained. This is reflected in the calculation of the next correction value. In this way, the accuracy of the correction value is further improved due to the learning effect.
[0015]
  Claims7Then, as illustrated in FIG. 15, the learning permission determining means 9 determines whether or not to learn the rotational speed deviation between the cylinders from the degree of rotational stability, and corrects for each cylinder only when the rotation is stable. The value calculation means 3 learns the rotational speed deviation between the cylinders, and when the rotation is unstable (for example, during misfire or transient), learning of the rotational speed deviation is prohibited to improve the learning accuracy.
[0016]
  Claims8Then, the learning permission determination means 9 calculates a parameter indicating the standard deviation or the degree of variation of the rotational speed fluctuation amount for all cylinders or for each cylinder as an index for determining the degree of rotational stability, and the parameter is equal to or less than a predetermined value. At this time, it is determined that the rotational state is stable, and learning of the rotational speed deviation between the cylinders is permitted. That is, as an index for determining the degree of rotation stability, a parameter representing the standard deviation or the degree of variation of the rotational speed fluctuation amount is calculated, whereby the degree of rotation stability is determined more accurately.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described below with reference to FIGS. An intake pipe 12 of the engine (internal combustion engine) 11 is provided with a throttle valve 13 and an intake pipe pressure sensor 14, and a fuel injection valve 15 is provided for each cylinder of the engine 11. The engine 11 is provided with a distributor 17 that sequentially distributes the high voltage generated by the igniter 16 to ignition plugs (not shown) of each cylinder. The distributor 17 is provided at a rate of once per two revolutions of the engine 11. A cylinder discrimination sensor 18 that generates a pulse signal is provided. A rotation angle sensor 19 is a rotation signal output means for outputting a pulsed rotation signal to the crankshaft (not shown) of the engine 11 every time a predetermined crank angle (30 ° C. in this embodiment) is rotated. Is provided. Further, a water temperature sensor 21 for detecting the cooling water temperature is attached to the water jacket 20 of the engine 11.
[0018]
Detection signals from these sensors are input to the control circuit 22. The control circuit 22 is composed of a microcomputer incorporating a CPU 23, ROM 24, RAM 25, input / output port 26, and the like. The control circuit 22 calculates the fuel injection amount and the ignition timing according to various engine control programs stored in the ROM 24 to control the operation of the engine 11, and misfires shown in FIGS. 3 and 4 stored in the ROM 24. The presence or absence of misfire in each cylinder is determined according to the determination program, and a warning lamp 27 is lit to warn the driver when a misfire occurs.
[0019]
Here, the principle of misfire determination in the present embodiment will be described using, for example, an in-line 6-cylinder engine as an example.
As shown in FIG. 5, the control circuit 22 calculates the ignition timing of each cylinder based on the rotation signal NE (pulse signal) output from the rotation angle sensor 19 every 30 ° C. A, and outputs an ignition signal. The period T302 from TDC (top dead center) immediately after ignition of each cylinder to ATDC (after top dead center) 30 ° C. has no effect on the rotational speed even at the time of misfiring, and the same rotation at the time of misfiring as at the time of normal combustion Is speed. However, in the subsequent period T300 from ATDC 60 ° C. to 90 ° C., the rotational speed does not increase as shown by the dotted line in FIG. 5 at the time of misfire, and there is a great difference from the rotational speed (solid line) during normal combustion. Therefore, the misfire can be determined by comparing the rotational speed fluctuation of TDC to ATDC 90 ° C. with a predetermined misfire determination value. Therefore, a rotational speed fluctuation amount ΔT between TDC and ATDC 90 ° C. A for each explosion stroke of each cylinder used for this misfire determination is calculated by the following equation (1) (see FIG. 6).
[0020]
ΔT = (T300−T302) − (T300′−T302 ′) (1)
Here, T302 and T302 'are the time (pulse interval) from TDC to ATDC 30 ° C A immediately after ignition, and T302' is the time before one rotation of the crankshaft (360 ° C A) of T302. T300 and T300 'are times (pulse interval) of ATDC 60 ° C to 90 ° C, and T300' is a time before one rotation of the crankshaft (360 ° A) of T300. In the above equation (1), T300-T302 is an equation for calculating the rotational speed difference corresponding to the instantaneous torque difference within one ignition cycle by converting it to time, and the latest rotational speed difference (T300-T302) The difference between the rotation speed difference (T300′−T302 ′) before one rotation is taken and the rotation speed fluctuation amount ΔT is converted into time and obtained.
[0021]
This rotational speed fluctuation amount ΔT is calculated for each ignition of each cylinder, but as shown in FIG. 7, the rotational speed fluctuation amount ΔT varies among cylinders even during normal combustion (solid line). In FIG. 7, the rotational speed fluctuation amount ΔT when each cylinder is misfired is indicated by a dotted line, but the rotational speed fluctuation amount ΔT varies among the cylinders during misfire as well as during normal combustion. As shown in FIG. 8, when an in-line 6-cylinder engine is used, the crankshaft 28 becomes long, and the position of the rotation angle sensor 19 facing the signal rotor 29 at one end of the crankshaft 28 (usually # 1 on the engine front side). The rotational speed detected by the rotational angle sensor 19 slightly shifts due to the twist of the crankshaft 28 between the cylinder on the cylinder side) and the cylinder in the explosion stroke, and this shift is one of the causes that increase the variation in the rotational speed fluctuation amount ΔT. It has become one.
[0022]
Thus, the rotational speed fluctuation amount ΔT for each cylinder explosion stroke varies among the cylinders. Therefore, as shown in FIG. 7, if a uniform misfire determination value is set for all cylinders, misfire cannot be detected at the time of misfire. Or misjudgment that misfire occurred during normal combustion.
[0023]
In order to solve this problem, as shown in JP-A-5-195858, the misfire determination value is corrected with a correction coefficient set in advance for each cylinder in accordance with the degree of variation in the combustion state of each cylinder. However, the degree of variation in the combustion state of each cylinder varies between engines, and also varies due to aging, so appropriate correction coefficients are set in advance for all engines. This is difficult, and moreover, it is impossible to properly deal with secular change, and there is a possibility that it may be misjudged although it is small.
[0024]
Therefore, in the present embodiment, the above problem is solved by correcting the rotational speed fluctuation amount ΔT of each cylinder as follows in accordance with the rotational speed deviation between the cylinders. As shown in FIG. 9, the rotational speed during the period T302 from TDC to ATDC 30 ° C. tends to be the fastest for the # 1 cylinder and the slowest for the # 6 cylinder. On the other hand, the rotational speed during the period T300 from ATDC 60 ° C. to 90 ° C. is substantially the same for all the cylinders # 1 to # 6 as shown in FIG. Further, in the in-line 6-cylinder engine, the ignition order is # 1 → # 5 → # 3 → # 6 → # 2 → # 4, and as shown in FIG. 6, the cylinder deviated from the # 1 cylinder by one rotation (360 ° C. A). Becomes # 6 cylinder. When the rotational speed deviation between the # 1 cylinder and the # 6 cylinder before one rotation is calculated, the rotational speed deviation becomes larger than the other cylinders as indicated by A in FIG. The # 5 cylinder calculates the rotational speed deviation with the # 2 cylinder before the one rotation, and the # 3 cylinder calculates the rotational speed deviation with the # 4 cylinder before the one rotation. The calculation of the rotational speed deviation is performed in a region where the rotational speed is not affected even in a misfire, that is, in a period T302 from TDC to ATDC 30 ° C.
[0025]
An example of the rotational speed deviation (T302-T302 ') of each cylinder is shown in FIG. The rotational speed deviation (T302-T302 ′) is maximum (A) immediately after ignition of the # 6 cylinder (ATDC 30 ° C. A), and is minimum (−A) immediately after ignition of the # 1 cylinder one rotation before (ATDC 30 ° C. A). ), But the absolute values of both are almost equal. Further, the absolute value B of the rotational speed deviation is the same for the # 5 cylinder and the # 2 cylinder before one rotation, and ± is reversed. Similarly, the absolute value C of the rotational speed deviation is the same between the # 3 cylinder and the # 4 cylinder before one rotation, and ± is reversed.
[0026]
In the present embodiment, the rotational speed fluctuation amount ΔT of each cylinder is corrected by the correction value TCYLi obtained according to the rotational speed deviation (A, B, C, -A, -B, -C) between the cylinders. Absorb (correct) the rotational speed deviation between the cylinders. At this time, as described above, the cylinders # 1, # 3, # 5 and the cylinders # 6, # 4, # 2 have the same absolute value of the rotational speed deviation, and only ± are reversed. The correction value TCYLi is calculated only for half of the cylinders # 1, # 3, and # 5, and for the remaining cylinders # 6, # 4, and # 2, correction values for the corresponding cylinders # 1, # 3, and # 5 are calculated. Use TCYLi.
[0027]
Hereinafter, the flow of the misfire determination process will be described with reference to the flowchart shown in FIG. In this routine, an interruption process is performed for each predetermined crank angle (every 30 ° C. in this embodiment) by a rotation signal NE (pulse signal) input from the rotation angle sensor 19. When the process is started, first, in step 101, the time required for the crankshaft 28 to rotate 30 ° C. A due to the difference between the current time TIMER of the free-run timer and the time TNEOLD at the time of the previous NE interruption ( After calculating tT30 (hereinafter referred to as “30 ° C. A time”), in step 102, the current time TIMER is stored in TNEOLD. In the next step 103, the 30 ° C. A time data T300, T301, T302, T303 are updated. Here, T300 is the current 30 ° C. A time, T 301 is the last 30 ° C. A time (before 30 ° C. A), T 302 is the last 30 ° C. A time (before 60 ° C. A), and T 303 is It is 30 ° C. A time two times before (90 ° C. A before).
[0028]
Thereafter, in step 104, it is determined whether or not the ATDC is 30 ° C. If the ATDC is 30 ° C, the learning process in the step 105 is executed. If not, the learning process is not executed. The process proceeds to step 106.
[0029]
The learning process (step 106) executed at ATDC 30 ° C. serves as a cylinder-specific correction value calculation unit that learns the rotation speed deviation between the cylinders and calculates a correction value corresponding to the rotation speed deviation for each cylinder. Fulfill. In this learning process, as shown in FIG. 4, first, in step 121, 30 ° C. A time data T3021, T3022, T3023 at ATDC 30 ° C. A are updated. Here, T3021 is 30 ° C A time before 120 ° C A, T3022 is 30 ° C A time before 240 ° C, and T3023 is 30 ° C A time before 360 ° A. Thereafter, in step 122, the latest 30 ° C. A time data T302 at ATDC 30 ° C. is stored in T3020, and in the next step 122, the difference (rotational speed deviation) between T3020 and T3023 of the previous rotation is TG. Calculate as
[0030]
In the next step 124, it is determined whether or not the ignition cylinder corresponds to any of # 1, # 3, and # 5. If any of # 1, # 3, and # 5, the process proceeds to step 125. The correction value TCYLi is calculated, and if it is any of # 2, # 4, and # 6, this routine is terminated without calculating the correction value TCYLi. As described above, cylinders # 1, # 3, and # 5 and cylinders # 6, # 4, and # 2 have the same absolute value of the rotational speed deviation, and only ± are reversed. , 125 is used to calculate the correction value TCYLi only for half of the cylinders # 1, # 3, and # 5, and for the remaining cylinders # 6, # 4, and # 2, the corresponding cylinders # 1, # 3, and # 5 The correction value TCYLi is used.
[0031]
Furthermore, in this embodiment, the correction value TCYLi is calculated by performing an annealing process according to the following equation (2).
TCYLi = {TCYLi (previous value) + 7 × TG} / 8 (2)
The above equation is 1/8 annealing, but may be any of 1/4, 1/2, 1/16,.
[0032]
After performing the learning process as described above, the process proceeds to step 106 in FIG. 3 to determine whether or not the temperature is ATDC 90 ° C. If it is not ATDC 90 ° C., this routine is performed without performing the subsequent processing. If ATDC90 ° C., the routine proceeds to step 107 where the rotational speed difference data ΔT301, ΔT302, ΔT303 corresponding to the instantaneous torque difference within one ignition cycle is updated. Here, ΔT301 is rotational speed difference data before 120 ° C. A, ΔT 302 is rotational speed difference data before 240 ° C. A, and ΔT 303 is rotational speed difference data before 360 ° A. In the next step 108, the rotational speed difference data ΔT300 corresponding to the instantaneous torque difference within the latest one ignition cycle is calculated from the difference between the 30 ° C. A time data T300 and T302.
[0033]
Thereafter, in step 109, the rotational speed fluctuation amount ΔT is calculated from the difference between the latest rotational speed difference data ΔT300 and the rotational speed difference data ΔT303 one rotation (360 ° C. A) before. The processing of step 109 functions as a rotational speed fluctuation amount calculation means in the claims. Next, in step 110, it is determined whether or not the ignition cylinder corresponds to any of # 1, # 3, and # 5. If any of # 1, # 3, and # 5, the process proceeds to step 111. The correction value TCYLi is added to the rotational speed fluctuation amount ΔT to correct the rotational speed fluctuation amount ΔT. On the other hand, if any of # 2, # 4, and # 6, the rotational speed fluctuation amount ΔT is corrected by subtracting the correction value TCYLj from the rotational speed fluctuation amount ΔT. At this time, when the ignition cylinder is # 2 (cylinder number i = 2), the correction value TCYLj (j = 5) of # 5 is used, and when # 4 (cylinder number i = 4), the correction value TCYLj of # 3 is used. When (j = 3) is used and # 6 (cylinder number i = 6), the correction value TCYLj (j = 1) of # 1 is used. The processing of these steps 111 and 112 functions as a rotational speed fluctuation amount correcting means referred to in the claims.
[0034]
After correcting the rotational speed fluctuation amount ΔT as described above, the routine proceeds to step 113, where the rotational speed fluctuation amount ΔT is compared with a predetermined misfire determination value LVLMF stored in the ROM 24, and if ΔT> LVLMF, A misfire is determined (step 114), and the warning lamp 27 is lit to warn the driver (step 115). On the other hand, if ΔT ≦ LVLMF, it is determined that the combustion is normal (step 116), and this routine is terminated. The processing of steps 113, 114, and 116 functions as misfire determination means in the claims.
[0035]
In the first embodiment described above, the misfire determination value is not corrected as in the prior art, but the rotational speed fluctuation amount ΔT is corrected by a correction value obtained by learning the rotational speed deviation between the cylinders. Since the rotational speed deviation between the cylinders is absorbed (corrected), it is possible to appropriately cope with variations between engines and aging, and to improve misfire determination accuracy. Moreover, since the learning timing of the rotational speed deviation between the cylinders is set immediately after ignition of each cylinder (a time when the influence of misfire does not appear), it becomes possible to learn the rotational speed deviation without being affected by misfire, Learning accuracy can be improved.
[0036]
Furthermore, the correction value (rotational speed deviation) for a specific cylinder and the correction value (rotational speed deviation) for a cylinder whose ignition timing is shifted by one revolution (360 ° C. A) are almost equal in absolute value, and ± is opposite. Since the correction value calculated for a specific cylinder is also used for a cylinder shifted by one revolution (360 ° C. A), the correction value calculation process is performed for half of the cylinders. The calculation load can be reduced. In the above embodiment, the correction values are calculated for the cylinders # 1, # 3, and # 5. However, the correction values may be calculated for the cylinders # 2, # 4, and # 6. In short, one cylinder from each set of two cylinders (# 1, # 6), (# 3, # 4), (# 5, # 2) whose ignition timing is shifted by one rotation (360 ° C. A) What is necessary is just to calculate a correction value.
[0037]
Of course, it goes without saying that correction values may be calculated for all cylinders. An embodiment embodying this is the second embodiment of the present invention shown in FIG. In the learning process of the second embodiment, the rotational speed deviation TGi of each cylinder is calculated by the same processes of steps 121 to 123 as in the first embodiment, and in step 126, the correction value TCYLi is calculated by the following equation (3). Is calculated.
[0038]
TCYLi = {| TGi | + | TGj |} / 2 (3)
Here, the subscripts i and j represent the cylinder numbers shifted by one rotation (360 ° C. A). Therefore, j = 6 when i = 1, j = 4 when i = 3, and j = 2 when i = 5.
[0039]
In this way, if the correction value TCYLi is obtained by averaging the absolute values of the rotational speed deviations TGi of the cylinders for the cylinders whose ignition timing is shifted by one revolution, the correction value is the same as in the case of the annealing process of the first embodiment. An excessive change in TCYLi can be moderately suppressed, and a reliable correction value TCYLi can be obtained.
[0040]
Further, the correction value may be learned for each engine load such as the intake air amount, the intake pipe pressure, the engine speed, and the like, and reflected in the calculation of the next correction value. An embodiment embodying this is the third embodiment of the present invention shown in FIG. In the third embodiment, the correction value is updated and stored in the corresponding learning area TCYLij according to the intake air amount GN detected by the intake air amount detecting means such as an air flow meter, and this is reflected in the calculation of the next correction value ( For example, the correction value is smoothed using the value of the learning area TCYLij). In this way, the accuracy of the correction value is further improved due to the learning effect.
[0041]
In the fourth embodiment of the present invention shown in FIG. 14, the rotational speed deviation between the cylinders is not learned. Instead, correction maps (a) and (b) set in advance for each cylinder are stored in the ROM 24. And a correction value is obtained from the correction map according to the engine load. Here, the correction map (a) is a map for storing a correction coefficient REij corresponding to the intake air amount GN for each cylinder, and the correction map (b) is a correction coefficient RFij corresponding to the engine speed for each cylinder. Is a map for storing From these correction maps (a) and (b), a correction value TCYLij is calculated by the following equation (4).
TCYLij = REij × RFij (4)
[0042]
Thus, if a correction value is obtained from the correction map according to the engine load, a correction value suitable for the engine operating state can be obtained. In the fourth embodiment, the intake air amount GN and the engine speed are used as the engine load. However, data representing other engine loads such as the intake pipe pressure may be used.
[0043]
In the third and fourth embodiments, maps are made only for the cylinders # 1, # 3, and # 5, and the cylinders # 6, # 4, and # 2 are # 1, # 3, and # 5, respectively. Although correction values for cylinders are used, it goes without saying that maps may be made for all cylinders.
[0044]
In each of the above embodiments, the learning process may be performed when signals representing engine operating conditions such as rotation change, load change, throttle opening, etc. are in a steady state, that is, when the rotation state is stable. preferable. Therefore, not only when a misfire occurs, but also when the automatic transmission is switched from the neutral to the drive range, when the air conditioner is switched on / off, when the electrical load (alternator load) is switched on / off, etc. The learning process is prohibited. Thereby, erroneous learning can be prevented in advance and learning accuracy can be improved.
[0045]
Hereinafter, a fifth embodiment of the present invention embodying this will be described with reference to FIGS. First, a method for calculating the rotational speed fluctuation amount ΔT will be described with reference to FIG. A rotation signal output from the rotation angle sensor 19 every 30 ° C. A time from the previous TDC to the next TDC, that is, a time T 120 required for the crankshaft 28 to rotate at 120 ° C. A (in the case of a 6-cylinder engine). Calculation is performed by integrating NE pulse intervals. Then, using the T120i calculated this time and T120i-3 before one rotation of the crankshaft (before 360 ° C. A), the rotational speed fluctuation amount ΔT is calculated by the following equation.
ΔT = T120i-T120i-3
[0046]
The calculation of the rotational speed fluctuation amount ΔT is performed by the NE interrupt routine shown in FIG. In this routine, an interrupt process is performed every predetermined crank angle (in this embodiment, every 30 ° C. A) in synchronization with the input of the rotation signal NE. When the processing is started, first, in step 201, the time required for the crankshaft 28 to rotate 30 ° C. A due to the difference between the current time TIMER of the free-run timer and the time TNEOLD at the time of the previous NE interruption ( After calculating tT30 (hereinafter referred to as “30 ° C. A time”), in step 202, the current time TIMER is stored in TNEOLD.
[0047]
In the next step 203, the 30 ° C. A time data T300, T301, T302, T303, and T304 are updated. Here, T300 is the current 30 ° C. A time, T 301 is the last 30 ° C. A time (before 30 ° C. A), T 302 is the last 30 ° C. A time (before 60 ° C. A), and T 303 is It is 30 ° C. A time two times before (90 ° C. A before), and T304 is 30 ° C. A time two times before (120 ° C. A before). In the next step 204, 30 ° C. A times T304 to T301 corresponding to the past 120 ° C. A are added together to calculate a time T120 required for the crankshaft 28 to rotate 120 ° C. A.
[0048]
On the other hand, the misfire determination routine shown in FIG. 18 is interrupted for each TDC. When the processing is started, first, in step 211, cylinder discrimination is performed to determine which cylinder data. This cylinder discrimination is performed by calculating the ignition order i from the value of the cylinder discrimination counter CCRNK counted up every time the rotation signal NE is input (every 30 ° C. A) (CCRNK returns to 0 when it exceeds 23). ).
i = CCRNK / 4 + 1
In the 6-cylinder engine, the ignition order is a repetition of # 1 → # 5 → # 3 → # 6 → # 2 → # 4, where # 1 when i = 1, # 5 when i = 2, i = 3 # 3 when i = 4, # 6 when i = 4, # 2 when i = 5, and # 4 when i = 6.
[0049]
Thereafter, in step 212, the difference between the current T120i and T120i-3 before one rotation of the crankshaft (before 360 ° C. A) is calculated to obtain the rotational speed fluctuation amount ΔTi. Then, in the next step 213, learning processing is executed. This learning process is executed by the learning process routine of FIG. In this learning process routine, first, in step 221, the standard deviation σ and the average value X of the rotational speed fluctuation amount ΔTi are calculated by the routine of FIG. The standard deviation σ and the average value X may be calculated for each predetermined number of ignitions, but here, the standard deviation σ and the average value X are calculated in real time using a probabilistic method as follows.
[0050]
First, in step 231, the current rotational speed fluctuation amount ΔTi and the current Yi (= X + σ) are compared. If ΔTi> Yi, the process proceeds to step 232, where 0.1 is added to the current Yi. When Yi is updated and ΔTi ≦ Yi, the process proceeds to step 233, and Yi is updated with a value obtained by subtracting 0.02 from the current Yi. Thereafter, the process proceeds to step 234, where the current rotational speed fluctuation amount ΔTi is compared with the current average value Xi. If ΔTi> Xi, the process proceeds to step 235, where 0.01 is added to the current Xi. Xi is updated, and if ΔTi ≦ Xi, the process proceeds to step 236, and Xi is updated with a value obtained by subtracting 0.01 from the current Xi. Thereafter, the process proceeds to step 237, where the current standard deviation σi is obtained by subtracting the current average value Xi from the current Yi, and this routine is terminated.
[0051]
Thereafter, the process returns to step 222 of the learning process routine of FIG. 19 to determine whether or not the value of the cylinder discrimination counter CCRNK is 0, that is, whether or not the TDC is # 1, and if “No”, This routine is terminated without performing the subsequent learning process. On the other hand, if CCRNK = 0 (TDC of # 1), the routine proceeds to step 223, where the standard deviation σj (j = 1 to 6) of the rotational speed fluctuation amount of each cylinder is compared with a predetermined value, and the rotation of each cylinder. The degree of variation in the speed fluctuation amount is determined. If σj ≧ predetermined value (variation is large), the process proceeds to step 224, the delay counter CDK is cleared to 0, and in the following step 225, the learning value of the correction value TCYLi is read, and this routine is terminated.
[0052]
On the other hand, if it is determined in step 223 that σj <predetermined value (variation is small), the process proceeds to step 226, where the delay counter CDK is counted up, and in step 227, the delay counter CDK reaches 15. It is determined whether or not. If the delay counter CDK is less than 15, this routine is terminated without updating the learning value. That is, if the state of σj <predetermined value (small variation) continues for 15 times or more, that is, only when the rotational state is stable, the process proceeds to step 228 to update the learning value, and the maximum of the average value X The value Xmax is calculated, and in the subsequent step 229, the correction value TCYLi is calculated by the following smoothing process.
TCYLi = {15 TCYLi (previous value) + (Xmax−Xi)} / 16
[0053]
The above formula is 1/16 annealing, but any of 1/4, 1/8,. The calculated correction value TCYLi is stored for each learning region, and this routine is terminated. The processing in steps 223, 226, 227 and the standard deviation σ / average value X calculation processing in FIG. 20 function as learning permission determination means in the claims.
[0054]
When the learning process routine is completed in this manner, the process returns to step 214 of the misfire determination routine of FIG. 18, and the correction value TCYLi is added to the rotation speed fluctuation amount ΔTi to correct the rotation speed fluctuation amount ΔTi. Then, in the next step 215, the rotational speed fluctuation amount ΔTi is compared with a predetermined misfire determination value LVLMF stored in the ROM 24. If ΔT> LVLMF, it is determined that misfire has occurred (step 216), and the warning lamp 27 Is lit to warn the driver (step 217). On the other hand, if ΔT ≦ LVLMF, it is determined that the combustion is normal (step 218), and this routine is terminated.
[0055]
In the fifth embodiment described above, the standard deviation σ of the rotational speed fluctuation amount ΔT is calculated, and the rotation is performed when the standard deviation σj of the rotational speed fluctuation amount ΔT of all the cylinders is less than a predetermined value for a predetermined number of times or more. Since it is judged that the state is stable and learning of the correction value TCYLi is permitted and learning is prohibited when the rotation is unstable (for example, at the time of misfire or transition), erroneous learning can be prevented. Learning accuracy can be improved.
[0056]
In step 227 of FIG. 19, it is determined whether or not the rotational state is stable depending on whether or not the state of σj <predetermined value is continued 15 times. However, this number is not limited to 15 times. , 14 times or less, or 16 times or more.
[0057]
In step 223 in FIG. 19, it is determined whether the standard deviation σj of the rotational speed fluctuation amount ΔT is less than a predetermined value for all the cylinders. However, this determination may be performed separately for each cylinder. good. In addition, the index for determining the degree of rotation stability is not limited to the standard deviation σ. In short, any parameter indicating the degree of variation in the rotational speed fluctuation amount ΔT for all cylinders or for each cylinder is calculated. It ’s fine.
[0058]
In addition, although each said embodiment applies this invention to a 6-cylinder engine, it is not restricted to this, It can apply similarly to an engine of 4 cylinders or more, and is not restricted to an inline engine, V This can also be applied to a type engine. In the above embodiment, the rotational speed deviation is learned based on the rotation signal NE (pulse signal) output every 30 ° C. A from the rotation angle sensor 19, but the pulse interval of the rotation signal NE is 30 ° C. Needless to say, the crank angle is not limited to A but may be other crank angles such as 15 ° C. A.
[Brief description of the drawings]
FIG. 1 is a block diagram showing three embodiments of the present invention.
FIG. 2 is a diagram showing a schematic configuration of the entire system according to the first embodiment of the present invention.
FIG. 3 is a flowchart showing a process flow of a misfire determination routine.
FIG. 4 is a flowchart showing a process flow of a learning process routine.
FIG. 5 is a time chart showing an example of fluctuations in rotational speed.
FIG. 6 is a diagram for explaining a method of calculating a rotational speed fluctuation amount ΔT.
FIG. 7 is a diagram for explaining variation in rotational speed fluctuation amount ΔT of each cylinder;
FIG. 8 is a diagram for explaining the positional relationship between each cylinder and a rotation angle sensor;
FIG. 9 is a diagram for explaining the relationship of T302 time (rotational speed difference) between TDC and ATDC 30 ° C. in each cylinder;
FIG. 10 is a diagram for explaining the relationship of T300 time (rotational speed difference) between ATDC 60 ° C. and 90 ° C. in each cylinder;
FIG. 11 is a time chart for explaining a rotational speed deviation between cylinders.
FIG. 12 is a flowchart showing a process flow of a learning process routine according to the second embodiment of the present invention.
FIG. 13 is a diagram conceptually showing a learning area in the third embodiment of the present invention.
FIG. 14 is a diagram conceptually showing correction maps (a) and (b) in a fourth embodiment of the present invention.
FIG. 15 is a functional block diagram conceptually showing a fifth embodiment of the present invention.
FIG. 16 is a view for explaining a calculation method of a rotational speed fluctuation amount ΔT in the fifth embodiment.
FIG. 17 is a flowchart showing the flow of processing of an NE interrupt routine.
FIG. 18 is a flowchart showing a process flow of a misfire determination routine.
FIG. 19 is a flowchart showing a process flow of a learning process routine.
FIG. 20 is a flowchart showing a processing flow of a standard deviation σ / average value X calculation processing routine;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Rotation signal output means, 2 ... Rotation fluctuation amount calculation means, 3 ... Cylinder correction value calculation means, 4 ... Rotational speed fluctuation amount correction means, 5 ... Misfire determination value storage means, 6 ... Misfire determination means, 7 ... Engine Load output means, 8 ... correction map storage means, 9 ... learning permission determination means, 11 ... engine (internal combustion engine), 14 ... intake pipe pressure sensor, 15 ... fuel injection valve, 18 ... cylinder discrimination sensor, 19 ... rotation angle sensor (Rotation signal output means), 22 ... control circuit (rotational fluctuation amount calculating means, cylinder-specific correction value calculating means, rotational speed fluctuation amount correcting means, misfire determination means), 27 ... warning lamp, 28 ... crankshaft.

Claims (8)

Rotation signal output means for outputting a rotation signal for each predetermined rotation angle according to the rotation of the internal combustion engine;
A rotational speed variation calculating means for calculating a rotational speed variation for each explosion stroke of each cylinder of the internal combustion engine based on the rotational signal;
Cylinder correction that learns the rotational speed deviation between the cylinders based on a signal during a period in which the misfire immediately after ignition does not appear among the rotational signals, and calculates a correction value according to the rotational speed deviation for each cylinder A value calculating means;
Rotational speed fluctuation amount correction means for correcting the rotational speed fluctuation amount for each explosion stroke of each cylinder calculated by the rotational speed fluctuation amount calculation means with the correction value calculated by the correction value calculation means for each cylinder;
A misfire determination means for comparing the rotation speed fluctuation amount for each explosion stroke of each cylinder corrected by the rotation speed fluctuation amount correction means with a predetermined misfire determination value to determine the presence or absence of misfire in each cylinder. A misfire detection device for an internal combustion engine characterized by the above.   2. The misfire detection of an internal combustion engine according to claim 1, wherein the cylinder-specific correction value calculation means learns a rotation speed deviation from a difference between a rotation speed immediately after ignition of each cylinder and a rotation speed before one rotation. apparatus.   The correction value calculation unit for each cylinder uses a correction value calculated for the specific cylinder as a correction value for a cylinder whose ignition timing is shifted by one revolution from the specific cylinder. Misfire detection device for internal combustion engine.   The misfire detection device for an internal combustion engine according to any one of claims 1 to 3, wherein the cylinder-specific correction value calculation means smoothes the correction value.   3. The internal combustion engine according to claim 1, wherein the cylinder-specific correction value calculating means obtains a correction value by averaging the learned absolute value of the rotational speed deviation for the cylinders whose ignition timing is shifted by one revolution. Misfire detection device.   6. The cylinder-specific correction value calculation means learns the correction value for each engine load and reflects it in the calculation of the next correction value. Misfire detection device for internal combustion engine.   The said cylinder specific correction value calculation means has a learning permission determination means which determines from the rotational stability degree whether to learn the rotational speed deviation between each cylinder. Misfire detection device for internal combustion engine.   The learning permission determining means calculates a parameter representing the standard deviation or the degree of variation of the rotational speed fluctuation amount for all cylinders or for each cylinder as an index for determining the degree of rotational stability, and when the parameter is a predetermined value or less 8. The misfire detection apparatus for an internal combustion engine according to claim 7, wherein learning of a rotational speed deviation between the cylinders is permitted.

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