JP2000213408A - Misfire detecting apparatus for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of misfire detection as well as to recognize a misfire detection period at a constant interval at all times. SOLUTION: A crank angle sensor 25 outputs a reference position signal corresponding to a predetermined reference position of a crankshaft 18. A ring gear angle sensor 26 outputs ring gear signals corresponding to passage of teeth of a ring gear 24. A microcomputer 33 in an ECU 30 measures time when the reference position signal is input and time when the ring gear signals are input. If an interval between the input time of the reference position signal and that of the ring gear signals is shorter than a predetermined time determined based on operation load and processing speed of a computer and a peripheral circuit thereof, association between the ring gear signal and a crank angle is prohibited. If the interval is longer than a predetermined time, the association between the ring gear signal and the crank angle is permitted. Further, the microcomputer 33 detects misfire of an engine 10 based on a fluctuation amount of revolution speed of the engine 10 in a misfire detection period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting misfire of an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, various devices for detecting misfire for each cylinder of an internal combustion engine using a microcomputer in a vehicle-mounted ECU have been proposed.
In some cases, an angular velocity is measured during a predetermined misfire detection period (angular velocity measurement section) for each cylinder, and the presence or absence of a misfire is detected based on a deviation of the angular velocity. In this method, the variation in the angular velocity measurement section has a great influence on the misfire detection accuracy.

[0003] In order to absorb the variation of the angular velocity measurement section for each cylinder and improve the accuracy, learning control using a smoothing operation or the like is generally performed, but the learning effect is reduced due to the mounting position of the crank angle sensor. In some cases, the misfire detection accuracy cannot be sufficiently obtained. For example, while a crank angle sensor is attached to the front side of the internal combustion engine,
If the opposite rear side is connected to the transmission side, undulation occurs on the front side during high rotation due to the effect of the mass difference on the crankshaft, and the accuracy of the angular velocity measurement section deteriorates.

As a countermeasure, it is conceivable to attach an angle sensor to a ring gear that rotates synchronously with the crankshaft, and use the detection signal of the ring gear side angle sensor instead of the detection signal of the crank angle sensor. That is, the angular velocity of each cylinder is measured from the passage of the ring gear teeth in the angular velocity measurement section, and misfire detection is performed according to the measurement result. Since the ring gear is arranged on the rear side of the crankshaft where undulation is unlikely to occur, it is possible to suppress variations in the angular velocity measurement section due to undulation.

[0005] Incidentally, as a prior art relating to misfire detection or learning control using a ring gear, Japanese Patent Laid-Open No. 4-113 is disclosed.
No. 244, Japanese Patent Application Laid-Open No. 4-1011071, Japanese Patent Application Laid-Open No. 10-18899, and the like.
It describes a method of associating a reference position of the crankshaft angle with an angular velocity measurement section of the ring gear, and a method of correcting a misalignment in the association.

[0006]

However, in the above prior art, it is inevitable that the angular velocity measurement section fluctuates due to the influence of the program processing speed and the processing timing when the internal combustion engine is rotating at a high speed, and improvement in accuracy cannot be expected. That is,
When associating the angular velocity measurement section defined by the predetermined crank angle with the ring gear angular position (ring gear tooth) and overlapping with the higher priority unspecified priority processing, each time, only a few teeth of the ring gear tooth are overlapped. The angular velocity measurement section shifts, and as a result, the accuracy of misfire detection deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to always recognize a misfire detection period in a fixed section, thereby improving the accuracy of misfire detection. An object of the present invention is to provide a misfire detection device for an internal combustion engine.

[0008]

When a ring gear is mounted on a crankshaft, the misalignment angle between the ring gear teeth and the crankshaft is determined at the time of mounting, and therefore, a misfire detection period (angular velocity) for measuring engine speed fluctuations. It is guaranteed that the position of the ring gear teeth within the measurement section) is always constant for each cylinder. In other words, if the misfire detection period can be accurately determined by the program, it is necessary to correct the deviation between the ring gear teeth and the crankshaft, and the accuracy can be improved.

According to the present invention, it is detected that the unspecified priority processing having a higher priority is performed from the input timing of the reference position signal to the processing for associating the ring gear signal with the crank angle. Focusing on the cause of the period shift, the influence of this unspecified processing is removed, and the detection accuracy is improved by eliminating the shift in the misfire detection period that occurs every time the engine is started.

According to the first aspect of the present invention, the first sensor outputs a reference position signal corresponding to a predetermined reference position of the crankshaft, and the second sensor outputs a ring gear corresponding to the passage of the teeth of the ring gear. Output a signal. Then, a misfire detection period is set at a predetermined crank angle, and misfire of the internal combustion engine is detected based on the amount of fluctuation of the engine speed during the misfire detection period. Also, a predetermined time from the input of the reference position signal,
The association between the ring gear signal and the crank angle is prohibited, and the association between the ring gear signal and the crank angle is performed after the lapse of the predetermined time.

According to the above configuration, the association between the ring gear signal and the crank angle is prohibited for a predetermined time from the input of the reference position signal. The inconvenience of overlapping with high priority processing is avoided. Then, after the predetermined time elapses and the priority processing ends, the association of the ring gear signal is performed for the first time. Therefore, variations in the misfire detection period due to the program processing load and the like are eliminated. As a result, it is possible to always recognize the misfire detection period in a certain section, and to improve the accuracy of misfire detection.

According to the second aspect of the present invention, the first measuring means of the microcomputer measures the time when the reference position signal is input, and the second measuring means measures the time when the ring gear signal is input. measure. The prohibition / permission means determines that the time interval between the input time of the reference position signal and the input time of the ring gear signal is shorter than a predetermined time determined based on the calculation load and processing speed of the computer and its peripheral circuits. ,
The association between the ring gear signal and the crank angle is prohibited, and the association between the ring gear signal and the crank angle is permitted when the time exceeds the predetermined time.

According to the above arrangement, when the time interval between the reference position signal and the ring gear signal becomes longer than a predetermined time determined on the basis of the calculation load and processing speed of the computer and its peripheral circuits, the ring gear is not generated until the time interval becomes longer. An association between the signal and the crank angle is performed. Therefore, similarly to the first aspect, at the beginning of the input of the reference position signal, the inconvenience of associating the ring gear signal with the higher priority processing is avoided, and the misfire detection period varies due to the program processing load and the like. Is eliminated. As a result, it is possible to always recognize the misfire detection period in a certain section, and to improve the accuracy of misfire detection.

According to the third aspect of the present invention, a serial number is sequentially assigned from the time when the association between the ring gear signal and the crank angle is permitted, and a misfire detection period is determined based on the serial number to perform misfire detection. Do. In such a case, since the positions of the ring gear teeth are unchanged, there is no problem that the misfire detection period is erroneously recognized and the accuracy of misfire detection is reduced, and simple and highly accurate misfire detection can be continued.

According to the fourth aspect of the present invention, a frequency dividing circuit for receiving the frequency dividing start signal and dividing the ring gear signal by a predetermined frequency dividing ratio is newly provided, and a predetermined time period from the input of the reference position signal is provided. When the time has elapsed, set an equivalent time corresponding to the preliminary period until the division of the divider circuit starts, wait for that time, and then
The frequency division is started by the frequency division start signal, and the ring gear signal after the frequency division is associated with the crank angle.

According to the above configuration, it is possible to always recognize the misfire detection period in a fixed section and to improve the accuracy of misfire detection in the same manner as in the first and second aspects. The division of the ring gear signal can be started at an appropriate time in consideration of the time required until the division is started. Therefore, when the misfire is detected using the ring gear signal after the frequency division, the detection accuracy can be improved.

According to the fifth aspect of the present invention, when skipping the m-number of ring gear signals after the division when waiting for the preliminary period until the division of the frequency dividing circuit is started, the divided ring gear signal and the divided ring gear signal are not read. From the time when the association with the crank angle is permitted,
The serial number is assigned with “original start number + m” as an initial value. In this case, deviation between the actual ring gear teeth and the serial number can be avoided, and highly accurate misfire detection can always be realized.

According to the present invention, the association between the ring gear signal and the crank angle is performed only once when the internal combustion engine is started. That is, if the influence of disturbance such as noise is not taken into account, it is not necessary to repeatedly perform the association between the ring gear signal and the crank angle, and since it is not performed repeatedly, the calculation load on the microcomputer can be greatly reduced.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings. In the device of the present embodiment, a four-cylinder four-cycle gasoline engine for a vehicle as an internal combustion engine is targeted, and an ECU (electronic control unit) that controls the engine controls a fuel injection amount to each cylinder based on an engine operating state. Control ignition timing optimally. Further, the ECU detects a misfire occurring in each cylinder based on the amount of change in the instantaneous rotational speed of the engine.

FIG. 1 is a configuration diagram showing an outline of an engine and its peripheral devices. The engine 10 includes first to fourth (#
1 to # 4) and the combustion order is # 1 →
# 2 → # 3 → # 4. An injector 12 is provided in the intake pipe 11 for each cylinder. Fuel fed from a fuel supply system (not shown) is distributed and supplied to the injectors 12 of the respective cylinders through the delivery pipe 13. When the injector 12 is driven to open for a time corresponding to the fuel injection amount commanded by the ECU 30, the fuel is injected and supplied in the order of the combustion cylinders. The fuel injected by the injector 12 is mixed with fresh air supplied from an upstream portion of the intake pipe 11, and the air-fuel mixture is introduced into the combustion chamber 15 via the intake valve 14.

A piston 16 is provided in the combustion chamber 15.
The piston 16 is connected to a crankshaft 18 via a connecting rod 17.
It is connected to. The air-fuel mixture introduced into the combustion chamber 15 is compressed therein, and is ignited by an ignition spark emitted from a spark plug 19 to explode. The engine 10 obtains rotational torque by this explosion. Further, the gas after combustion is discharged to the exhaust pipe 21 via the exhaust valve 20 as exhaust gas. The ignition plug 19 generates the above-mentioned ignition spark by applying a high voltage which is boosted by an ignition coil (not shown) and distributed to each cylinder by a distributor.

On the rear side (transmission side not shown) of the crankshaft 18, the driving force of the starter motor 23 is rotated synchronously with the crankshaft 18 and the driving force of the starter motor 23 is applied.
A ring gear 24 for transmitting the power to the vehicle is provided. The ring gear 24 has a number of convex teeth carved at equal intervals all around its circumference. Therefore, when a starter key (not shown) is operated to the ON position, the initial rotation is given to the crankshaft 18 by the driving force of the starter motor 23, and the engine 10 is started.

The crank angle sensor 25 is connected to the crankshaft 18
At a predetermined crank angle (45 ° in the present embodiment) as the crankshaft 18 rotates.
A rotation angle detection signal is generated each time the motor rotates by CA). That is, the crank angle sensor 25 is a known electromagnetic pickup type sensor, and electromagnetically detects the proximity of a projection of a rotating disk (not shown) at every 45 ° CA. Further, the rotating disk is provided with a toothless portion in which the protrusion is missing by one tooth, and the reference position of the crank angle can be detected by the toothless portion.

The ring gear angle sensor 26 detects the ring gear 2
4, and electromagnetically detects the proximity of each tooth of the ring gear 24. Each detection signal of the crank angle sensor 25 and the ring gear angle sensor 26 is taken into the ECU 30, and is shaped into a rectangular signal by the waveform shaping circuits 31, 32 in the ECU 30. In the present embodiment,
The crank angle sensor 25 corresponds to a “first sensor”, and the ring gear angle sensor 26 corresponds to a “second sensor”.

In the ECU 30, CPU, ROM, R
A well-known microcomputer (hereinafter, referred to as a microcomputer) 33 including an AM, a backup RAM, and the like is provided with pulse signals of the crank angle sensor 25 and the ring gear angle sensor 26 input through the waveform shaping circuits 31 and 32,
In addition, based on the engine operating conditions such as the intake pipe pressure at the time, engine cooling water, throttle opening, etc., the RO
The drive control signals for the injector 12 and the spark plug 19 are calculated according to the control program stored in M. Then, the control signal is output to the drive circuit 34 to optimally control the fuel injection amount and the ignition timing.

The microcomputer 33 detects engine misfire from the rotational speed of each cylinder of the engine for each explosion stroke.
Upon detection of this misfire, the microcomputer 33 defines an angular velocity measurement period for each cylinder by a serial number (ring gear tooth number) assigned to each ring gear tooth, and determines a misfire based on the variation in angular velocity in the angular velocity measurement section. Detect presence / absence. In the present embodiment, the angular velocity measurement section corresponds to a “misfire detection period”.

Next, the operation of the present embodiment will be described. FIG. 2 is a time chart showing the basic operation of fuel injection and ignition timing control. In FIG. 2, a crank angle signal (pulse signal after waveform shaping) by the crank angle sensor 25 is output at 45 ° CA intervals, and the crank angle signal
Each time a piece is detected, the reference position is recognized by the missing tooth portion.
In other words, the moment when the crank angle signal is input immediately after the missing tooth means the moment when the crank angle is at the reference position.

The crank tooth indicating the reference position of the crank angle is set to Cne = 0, and thereafter, every time a crank angle signal is input, Cne = 1, 2, 3... Give. By terminating the numbering at the stage when the crankshaft 18 has made one revolution, the crank tooth number C
ne can be regarded as “relative angle from the crank reference position”, and the ignition signal and the fuel injection signal of each cylinder are controlled based on the crank tooth number Cne. At this time, # 1,
The ignition signals of the # 3 cylinder and the # 2 and # 4 cylinders are
Each is output simultaneously at a predetermined crank angle position.
Further, the fuel injection signal of each cylinder is output in the order of the combustion cylinder in the exhaust or intake stroke.

Next, a procedure for assigning a ring gear tooth number at the beginning of engine start will be described with reference to a time chart of FIG. The ring gear 24 usually has a large number of teeth, for example, about 120 (different for each engine model), but in the following description, 16 ring gear teeth will be used for convenience.

Since the ring gear 24 has no missing teeth due to its nature, the ring gear angle sensor 26 alone cannot determine the relative angle from the reference position. Therefore, in order to determine the reference position of the ring gear teeth, the timing for determining a specific crank tooth number is used. Here, the ring gear tooth number C is set while corresponding to the crank tooth number Cne = 0.
An example in which rg = 0 is determined will be described. Note that this numbering need not be performed twice or more each time the engine is started unless erroneous detection due to noise or the like is considered.

In FIG. 3, crank tooth number Cne = 0
The input time of the crank angle signal (reference position signal) is “Tcne”, and the input time of the ring gear angle signal is “Tcr”.
g ", the maximum time in which the input processing of the ring gear angle signal is waited for the program processing when the crank tooth number Cne = 0 or the higher priority program processing is" Tma
x ”. Tmax corresponds to a predetermined time determined based on the calculation load and processing speed of the computer and its peripheral circuits.

In such a case, even if a ring gear angle signal is input immediately after Cne = 0 (immediately after the reference position), the processing is not immediately performed, and the next ring gear angle signal may be input before processing. Therefore, in order to ensure that the correspondence between the actual ring gear tooth and the ring gear tooth number Crg is the same each time the engine is started, Tcrg-Tcne> Tmax must be satisfied.

That is, in an operation range of "Tmax <input interval of the ring gear angle signal", for example, under the condition of 1000 rotations or less, the numbering of the ring gear teeth is prohibited while Tcrg-Tcne≤Tmax. Then, after Tcrg-Tcne> Tmax, when the first ring gear angle signal is input, “Crg
= 0 "to initialize the ring gear tooth number Crg.
Thereafter, every time the ring gear angle signal is input, Crg = 1, 2,
Ring gear tooth number Crg is assigned as 3, ..., 15,
The numbering ends when the ring gear 24 has made one revolution.
Since the ring gear tooth number Crg can be regarded as “the relative angle of the ring gear 24 from the reference position”, it can be used to specify the angular velocity measurement section of the ring gear 24.

Since the ring gear 24 rotates synchronously with the crankshaft 18 on the crankshaft axis, the "ring gear 24
It is possible to perform misfire detection based on the angular velocity of the ring gear 24 as "the angular velocity of the crankshaft 18 = the angular velocity of the crankshaft 18". According to FIG. 4 showing the basic operation of misfire detection, if a misfire occurs at the ignition at time t1 in the figure, the deviation of the angular velocity obtained in the angular velocity measurement section for each cylinder fluctuates greatly. Then, when the deviation exceeds a predetermined misfire determination level, it is determined that a misfire has occurred.

FIG. 5 is a flowchart showing a process executed by the microcomputer 33 as an interrupt process every time a crank angle signal is input. In FIG. 5, in step 101, it is determined whether or not the crank angle signal at that time corresponds to the reference position. Specifically, the input interval (time interval) of the previous crank angle signal and the current crank angle signal are compared. For example, if the current input interval / previous input interval> 1.5 is established, immediately after passing the toothless portion, Assuming that
After making an affirmative determination in step 101, the process proceeds to step 102.

In step 102, the crank tooth number Cn
e is cleared to "0". In the following step 103, the current time is stored as Tcne, and then the present process is terminated. If step 101 is NO, step 1
The process proceeds to 04, where the crank tooth number Cne is incremented by "1", and this processing ends.

FIG. 6 is a flowchart showing a process executed by the microcomputer 33 as an interrupt process every time a ring gear angle signal is input. In FIG. 6, step 2
At 01, the current time is stored as Tcrg, and at subsequent step 202, it is determined whether or not the numbering completion flag Xcrgok is "1". Here, Xcrgok
= 0 indicates that the numbering of the ring gear teeth has not been completed after the engine is started, and Xcrgok = 1 indicates that the numbering of the ring gear teeth has been completed.

If Xcrgok = 0, step 203
Then, it is determined whether or not the engine speed Ne at that time is 1000 rpm or less, and further, Ne ≦ 1000 rpm
In step 204, it is determined whether or not the interval between the input time Tcrg of the ring gear angle signal and the input time Tcne of the crank angle signal at the reference position (Cne = 0) is longer than a predetermined time. . That is, it is determined whether or not Tcrg> Tcne + Tmax is satisfied.

If step 204 is YES,
In step 205, the numbering completion flag Xcrgok
Is set to "1", and in the subsequent step 206, the ring gear tooth number Crg is set to "0".

When Xcrgok = 1 is set, thereafter, step 202 becomes YES and steps 207 to 207 are executed.
209 is executed. That is, in step 207, it is determined whether or not the ring gear tooth number Crg is a predetermined value KC (KC = 15 in the present embodiment), and Crg = KC
If so, the ring gear tooth number Crg is cleared to "0" (step 208), and if Crg ≠ KC, the ring gear tooth number Crg is incremented by "1" (step 209).

FIG. 7 is a flowchart showing a misfire detection process, which is executed by the microcomputer 33 as an interrupt process for each input of a ring gear angle signal. In this misfire detection process, the angular velocity ω in a predetermined angular velocity measurement section is calculated for each combustion cylinder, and the presence or absence of a misfire is determined for each cylinder based on the angular velocity ω. The angular velocity measurement section may be set in a corresponding section including the compression TDC of each cylinder, and is set, for example, in a width of about 100 to 180 ° CA.

In FIG. 7, first, at step 301,
The ring gear tooth number Crg at that time is determined. The microcomputer 33 recognizes the angular velocity measurement section in association with the ring gear tooth number Crg. If the ring gear tooth number Crg matches the start time of the angular velocity measurement section, the process proceeds to step 302, where the current time is measured and measured. Is stored as “T1”.

If the ring gear tooth signal Crg coincides with the end time of the angular velocity measurement section, the routine proceeds to step 303, where the current time is measured and stored as "T2". Further, in step 304, the required time in the angular velocity measurement section for the current combustion cylinder is calculated, and the angular velocity ω of the crankshaft is calculated for each cylinder from the required time. More specifically, the measured times T1 and T2 are used, and based on the measured times T1 and T2, the angular velocity ω is calculated in the form of ω = KOMG / (T2−T1). In the above equation, the coefficient KOMG is a conversion coefficient for obtaining the rotational angular velocity (rad: radian) of the crankshaft.

Thereafter, in step 305, a deviation Δω of the angular velocity is calculated. That is, using the previous value of the angular velocity ωi-1 and the current value ωi, the angular velocity deviation Δω is calculated as Δω = (ωi−ωi−1) −FLN. Here, FLN is a learning value for eliminating individual differences and errors between cylinders.

After calculating the angular velocity deviation Δω, step 306
Then, the learning value FLN is updated. At this time,
A learning value FLN for reducing the angular velocity deviation for each cylinder is obtained, and that value is stored in the backup RAM in the microcomputer 33.

Thereafter, in step 307, it is determined whether or not the angular velocity deviation Δω is larger than a predetermined misfire determination level KDH. In step 308, it is determined whether or not the angular velocity deviation Δω is smaller than a predetermined misfire determination level KDL. Is determined. If both steps 307 and 308 are NO (K
If DL ≦ Δω ≦ KDH), it is determined that there is no misfire, and this processing is terminated.

If any of steps 307 and 308 is YES, the process proceeds to step 309, where it is determined that a misfire has occurred in the corresponding cylinder. At this time, a flag indicating the occurrence of misfire is set to "1", or the driver is alerted to that effect through lighting lamp lighting control or the like. In step 301, if the ring gear tooth number Crg is neither the start time nor the end time of the angular velocity measurement section, the present process ends.

In step 306, a learning process is performed according to the procedure shown in FIG. That is, step 40
In step 1, it is determined whether or not the angular velocity change is considered to be small. Specifically, it is determined whether or not the change in the engine load state due to ON / OFF switching of the air conditioner is small and the fluctuation range of the engine speed is small. Then, as long as step 401 is YES, the process proceeds to step 402 to calculate a smoothed value of the angular velocity deviation Δω. At this time, an average value is calculated by, for example, 1/8 average operation. Thereafter, in step 403, it is determined whether or not the number of samples of the angular velocity deviation Δω has reached a predetermined value (for example, 10). If YES, the smoothed value is changed to the learning value FL.
N is stored in the backup RAM.

In this embodiment, step 1 in FIG.
03 corresponds to “first measuring means”, step 201 in FIG. 6 corresponds to “second measuring means”, and steps 204 to 206 in FIG.
Correspond to “prohibition / permission means”, respectively.

According to the present embodiment described in detail above, the following effects can be obtained. (A) If the time interval between the input time Tcne of the reference position signal (Cne = 0) and the input time Tcrg of the ring gear angle signal is shorter than the predetermined time Tmax, the ring gear angle signal (ring gear teeth) The association between the ring gear angle signal and the crank angle is permitted when the time exceeds the predetermined time Tmax. According to this configuration, the association of the ring gear angle signal is performed only after the predetermined time Tmax elapses and the priority processing ends. Therefore, immediately after Cne = 0, the inconvenience of associating the ring gear angle signal with the higher priority processing is avoided, and the variation in the angular velocity measurement section due to the program processing load or the like is eliminated.
As a result, the angular velocity measurement section is always recognized as a fixed section,
As a result, the accuracy of misfire detection can be improved.

In such a case, the misalignment angle between the ring gear teeth and the crankshaft is determined at the time of assembly. Therefore, the position of the ring gear teeth in the angular velocity measurement section is guaranteed to be always constant for each cylinder, and the angular velocity measurement section can be accurately determined by a program. There is no need for modification.

(B) There is no deviation in the angular velocity measurement section every time the engine is started, and the variation in the angular velocity measurement section between the cylinders is absorbed by learning, so that the learning effect can be sufficiently exhibited. The accuracy of misfire detection is greatly improved.

(C) After associating the ring gear angle signal with the crank angle, a ring gear tooth number Crg is sequentially assigned, and an angular velocity measurement section is determined based on the ring gear tooth number Crg to detect misfire. did. In this case, since the positions of the ring gear teeth are unchanged, there is no problem that the angular velocity measurement section is erroneously recognized and the accuracy of misfire detection is reduced, and simple and highly accurate misfire detection can be continued.

(D) The association between the ring gear angle signal and the crank angle is performed only once when the engine is started. That is, unless the influence of disturbance such as noise is taken into account, it is not necessary to repeatedly execute the association between the ring gear angle signal and the crank angle, and since the association is not performed repeatedly, the calculation load on the microcomputer 33 can be greatly reduced. .

(Second Embodiment) Next, a second embodiment of the present invention will be described. However, in the configuration of the second embodiment, the same components as those of the above-described first embodiment are denoted by the same reference numerals and the description thereof is simplified. The following description focuses on differences from the first embodiment.

Since the ring gear 24 has a large number of teeth, if the program processing is performed every input of the ring gear angle signal as described above, the processing capability of the microcomputer 33 may be insufficient. Therefore, in the present embodiment, in order to perform misfire detection with high accuracy while reducing the microcomputer processing load, as shown in FIG. 9, a frequency dividing circuit 40 capable of designating a frequency dividing start timing by a frequency dividing start signal. Is added to the ECU 30.

Here, the frequency dividing circuit 40 takes in the ring gear angle signal after the waveform shaping, frequency-divides the signal at a predetermined frequency dividing ratio, and outputs a high or low binary signal. Actually, as shown in FIG. 10, when the frequency division start signal goes to the active level, the ring gear angle signal is frequency-divided by the frequency division ratio = 2 thereafter, and the frequency-divided signal is input to the microcomputer 33. Is done.
Before the start of frequency division, a ring gear angle signal without frequency division is input to the microcomputer 33.

FIG. 11 is a time chart showing a procedure for assigning a ring gear tooth number at the beginning of engine startup. However, in FIG. 11, for convenience, the number of ring gear teeth is 32 (actually, more than that, for example, about 120).

In FIG. 11, the crank tooth number Cne =
The input time of the crank angle signal (reference position signal) that becomes 0 is “Tcne”, the input time of the ring gear angle signal before frequency division is “Tcb (0), (1), (2)”, and the crank tooth number C
The maximum time in which the input processing of the ring gear angle signal after frequency division is waited for the program processing when ne = 0 or the program processing with higher priority is set to “Tmax”.

Input time Tcb (0) of the first ring gear angle signal that satisfies Tcb-Tcne> Tmax
In this state, the association of the ring gear angle signal is allowed. Therefore, it is desired to set the ring gear tooth number Crg to “0” at time Tcb (0) and obtain a signal edge after frequency division. However, it is impossible to immediately start frequency division by the frequency dividing circuit 40. It is. That is, even if the frequency division is started immediately, the frequency division start position is shifted by at least one tooth.

On the other hand, even if the start of frequency division is waited, if the signal edge after frequency division does not coincide with the original position, the ring gear tooth number C counted based on the ring gear angle signal after frequency division is counted.
rg shifts. As a result, the correspondence between the actual ring gear teeth and the ring gear tooth numbers Crg does not become the same every time the engine is started.

Therefore, when the frequency dividing circuit 40 divides the frequency by N, the input time Tcb (N) of the N-th ring gear angle signal from the time Tcb (0) is set to the time from the time Tcb (N) until the frequency dividing of the frequency dividing circuit 40 starts. The time is set to be later than the output time of the frequency division start signal from the microcomputer 33 in consideration of the delay time. That is, the ON timer is set so that the microcomputer 33 outputs the frequency division start signal immediately after the input of the ring gear angle signal to the microcomputer at the time Tcb (N-1). In FIG. 11, N =
2, the frequency division start signal is raised to the active level between times Tcb (1) and Tcb (2).

In this case, since the original frequency-divided signal is skipped by one, the ring gear tooth number C is set to "Crg = 1".
Initialize rg. Thereafter, since all the ring gear angle signals are frequency-divided and input to the microcomputer 33, the ring gear tooth number Crg is given as Crg = 2, 3,. The numbering is terminated when the gear 24 has made one revolution.

Thus, when the next reference position is detected, the frequency division signal (ring gear tooth) immediately after "Tcne + Tmax" again becomes Crg = 0, and the correspondence between the actual ring gear tooth and the ring gear tooth number Crg is obtained. Is guaranteed at each start.

FIG. 11 shows an example in which only one frequency-divided signal is skipped when waiting for the set time of the ON timer (preliminary period until the start of frequency division).
When skipping the divided signals of the individual, "Crg = m"
Initially set the ring gear tooth number Crg as
rg = m + 1, m + 2,..., ring gear tooth number Cr
g may be counted.

FIG. 12 is a flowchart showing a process executed by the microcomputer 33 as an interrupt process every time a ring gear angle signal is input, and is executed in place of the process of FIG.

In FIG. 12, in step 501, the current time is stored as Tcb, and in subsequent step 502, it is determined whether or not the numbering completion flag Xcrgok is "1". If Xcrgok = 0, step 5
At 03, it is determined whether or not the frequency division start counter Ccrgok is “0 (initial value)”. On condition that Ccrgok = 0, at step 504, the input time Tcb of the ring gear angle signal and the reference position are set. It is determined whether or not the interval between the input time Tcne of the crank angle signal at (Cne = 0) is longer than a predetermined time. That is, it is determined whether or not Tcb> Tcne + Tmax. Then, step 504 is Y
In step 505, the frequency division start counter Ccrgok is set to “N−1” (N is a frequency division ratio) on the condition that it is ES.

Thereafter, in step 506, the ON timer of the frequency division start signal is set, and in step 507,
It is determined whether or not the frequency division start counter Ccrgok is “0”. At first, since Ccrgok> 0, this processing is ended as it is.

In the next process, NO is determined in step 503 because Ccrgok> 0, and the frequency division start counter Ccrgok is decremented by "1" in step 510. Then, Ccrgok is obtained by the subtraction in step 510.
When = 0, step 507 becomes YES, and in step 508, the numbering completion flag Xcrgok is set to “1”, and in step 509, the ring gear tooth number Crg is set to “1”.

When Xcrgok = 1 is set, thereafter, step 502 becomes YES, and step 511 counts the ring gear tooth number Crg. That is, similarly to steps 207 to 209 in FIG. 6, the ring gear tooth number Crg is set to the predetermined value KC (in the present embodiment, KC = 1
Until 5), the ring gear tooth number Crg is incremented by "1", and when Crg = KC, the ring gear tooth number Crg is cleared to "0".

According to the second embodiment, as in the first embodiment, the angular velocity measurement section can always be recognized in a fixed section, and the accuracy of misfire detection can be improved. . In addition to that, (A) a corresponding time (ON timer) corresponding to a preliminary period until the frequency division circuit 40 starts frequency division is set and waited for that time, and then the ring gear angle signal and the crank after the frequency division are set. Since the association with the angle is performed, the division of the ring gear angle signal can be started at an appropriate time in consideration of the time required until the division is started. Therefore, when the misfire is detected using the ring gear angle signal after the frequency division, the detection accuracy can be improved. (B) When skipping m frequency-divided signals while waiting for the preliminary period until the frequency division circuit 40 starts frequency division, the ring gear tooth number Crg is assigned with "original start number + m" as an initial value. In this case, a deviation between the actual ring gear tooth and the ring gear tooth number Crg can be avoided, and highly accurate misfire detection can always be realized.

The embodiment of the present invention can be embodied in the following forms other than the above. In the above embodiments, the angular velocity ω in the angular velocity measurement section is calculated, and the presence or absence of a misfire is detected from the deviation Δω. However, other methods may be used. For example, the presence or absence of a misfire may be detected from the amount of change in the instantaneous rotation speed during the misfire detection period for each cylinder. In short, it is only necessary to detect the misfire of the engine based on the fluctuation amount of the engine speed during the misfire detection period.

In each of the above embodiments, the crank tooth number “Cne = 0” is used as the reference position of the crank angle, and Cne =
The association between the ring gear teeth and the crank angle is performed after Tmax has elapsed from the detection of 0 (time Tcne), but this is changed. For example, other crank teeth numbers (0
Other than n) as a reference position, and from detection of Cne = n to T
The association between the ring gear teeth and the crank angle may be performed after the lapse of max.

In each of the above embodiments, the crank angle sensor 25 is referred to as the "first sensor" and the reference position is recognized from the missing tooth portion detected by the sensor 25. However, this configuration is changed. For example, a reference position sensor that outputs one pulse signal at the reference position may be separately provided. Further, the reference position may be detected by rotation of the cam shaft.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating an outline of a misfire detection device for an internal combustion engine according to an embodiment.

FIG. 2 is a time chart showing a basic operation of fuel injection and ignition timing control.

FIG. 3 is a time chart showing a procedure for assigning a ring gear tooth number.

FIG. 4 is a time chart showing a basic operation of misfire detection.

FIG. 5 is a flowchart showing a crank angle signal input interrupt process;

FIG. 6 is a flowchart showing a ring gear angle signal input interrupt process.

FIG. 7 is a flowchart showing a misfire detection process.

FIG. 8 is a flowchart showing a learning process.

FIG. 9 is a schematic diagram showing a configuration inside an ECU according to the second embodiment.

FIG. 10 is a time chart showing a signal waveform by frequency division.

FIG. 11 is a time chart showing a procedure for assigning a ring gear tooth number.

FIG. 12 is a flowchart illustrating a ring gear angle signal input interrupt process according to the second embodiment;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Engine, 18 ... Crankshaft, 24 ... Ring gear, 25 ... Crank angle sensor as 1st sensor, 2
6 ... Ring gear angle sensor as second sensor, 30 ...
ECU, 33 ... first measuring means, second measuring means, microcomputer as prohibiting / permitting means, 40 ... frequency dividing circuit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G087 AA01 BB14 CC01 CC03 EE23 3G019 CD09 DC06 GA01 GA02 GA16 LA05 3G084 CA01 DA04 EA05 EA07 EA08 EA11 EB20 EB25 EC02 FA24 FA34 FA38 FA39

Claims (6)

[Claims] 1. A ring gear attached to a crankshaft of an internal combustion engine, a first sensor for outputting a reference position signal corresponding to a predetermined reference position of the crankshaft, and a ring corresponding to passage of teeth of the ring gear A second sensor for outputting a gear signal, wherein a misfire detection period is set at a predetermined crank angle, and a misfire of the internal combustion engine is detected based on a fluctuation amount of the engine rotation speed during the misfire detection period. A misfire detection device, wherein the association between the ring gear signal and the crank angle is prohibited for a predetermined time from the input of the reference position signal, and the association between the ring gear signal and the crank angle is performed after the lapse of the predetermined time. A misfire detection device for an internal combustion engine, comprising: 2. A ring gear attached to a crankshaft of an internal combustion engine, a first sensor for outputting a reference position signal corresponding to a predetermined reference position of the crankshaft, and a ring corresponding to passage of a tooth of the ring gear. A second sensor that outputs a gear signal; and a microcomputer that sets a misfire detection period at a predetermined crank angle and detects misfire of the internal combustion engine based on the amount of fluctuation of the engine speed during the misfire detection period. An apparatus for detecting a misfire of an internal combustion engine, comprising: a first measuring means for measuring a time when the reference position signal is input; and a second measuring means for measuring a time when the ring gear signal is input. The time interval between the input time of the reference position signal and the input time of the ring gear signal is based on the arithmetic load and processing speed of the computer and its peripheral circuits. When the time is shorter than the predetermined time determined, the association between the ring gear signal and the crank angle is prohibited, and when the time is longer than the predetermined time, the prohibition / permission means for permitting the association between the ring gear signal and the crank angle is provided. A misfire detection device for an internal combustion engine, comprising: 3. A misfire detection apparatus for an internal combustion engine for detecting a relative angle from a reference position of a crankshaft based on a serial number assigned to a ring gear signal and associating the ring gear signal with a crank angle. 3. The misfire detection device for an internal combustion engine according to claim 1, wherein the serial numbers are assigned in order from a time point when the misfire is permitted, and a misfire detection period is determined based on the serial numbers to perform misfire detection. 4. 4. A ring gear attached to a crankshaft of an internal combustion engine, a first sensor for outputting a reference position signal corresponding to a predetermined reference position of the crankshaft, and a ring corresponding to passage of teeth of the ring gear A second sensor that outputs a gear signal; and a frequency divider circuit that receives the frequency division start signal and divides the ring gear signal by a predetermined frequency division ratio, and sets a misfire detection period at a predetermined crank angle. A misfire detection device for an internal combustion engine that detects a misfire of the internal combustion engine based on an amount of change in the engine rotation speed during the misfire detection period, wherein when a predetermined time has elapsed from the input of the reference position signal,
Set the equivalent time corresponding to the preliminary period until the frequency division circuit starts to divide, wait for that time, and then start frequency division by the frequency division start signal, and associate the ring gear signal with the crank angle after frequency division with the crank angle A misfire detection device for an internal combustion engine. 5. A misfire detecting apparatus for an internal combustion engine, wherein a serial number is assigned to a ring gear signal after frequency division and a relative angle from a reference position of a crankshaft is detected based on the number. When skipping m divided ring gear signals while waiting for the preliminary period until the start of the lap, if the association between the divided ring gear signals and the crank angle is permitted, the "initial start" The misfire detection device for an internal combustion engine according to claim 4, wherein the serial number is assigned with "number + m" as an initial value. 6. The misfire detection device for an internal combustion engine according to claim 1, wherein the association between the ring gear signal and the crank angle is performed only once when the internal combustion engine is started.