JPH0932626A - Misfire diagnosing device of engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an erroneous diagnosis for misfire determination by checking a learning value backed up during the previous operation to be used as it is or not at the time of diagnosis during the operation at every start of operation. SOLUTION: A misfire diagnosing device is provided with a time measuring means 21 for measuring the time required for a designated crank angle section corresponding to a combustion stroke by each cylinder, a learning value for correcting dispersion in the measured values of each cylinder is computed by a learning value arithmetic means 22, and the learning value is stored in a back-up memory 23 even after an engine is stopped. Before the operation of the learning value in this time operation, misfire is determined in a misfire determination means 24 from the fluctuation condition of a value obtained by correcting the measured value in this time operation by the learning value stored in the memory 23. It is determined by a position determination means 25 at every operation whether a designated crank angle section is in the same position as that of the previous operation or not, and if it is determined to be NO, misfire determination is prohibited by a misfire determination prohibiting means 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine misfire diagnosis device.

[0002]

2. Description of the Related Art There is a method of diagnosing a misfire by detecting a torque fluctuation of a crankshaft due to a misfire as a periodic fluctuation by a magnetic pickup provided opposite to a ring gear (Japanese Patent Laid-Open No. 4-113244). Reference).

To explain this, a shown in FIG.
Each of the sections b and c is a predetermined crank angle section provided corresponding to each combustion stroke of the V-type 6-cylinder engine, and the measured value TINT of the time required for each section is from the latest measured value TINT.
Sampled as NT1, TINT2, ..., TINT9.

For example, when a misfire occurs in the first cylinder during deceleration, a difference in level occurs in the measured value before and after the misfire as shown in FIG. However, the ignition order is 1-2-3-4-5-6.

In this case, since the No. 1 cylinder and No. 4 cylinder are measured at the same tooth position of the ring gear, the portion protruding above the diagonal straight line connecting the No. 4 cylinders (that is, TINT3 and TINT9) It can be estimated that the time increase ΔTINT1 is due to the misfire of the first cylinder. The time increase .DELTA.TINT1 in the figure is calculated by the equation: .DELTA.TINT1 = {3 (TINT6-TINT9) +3 (TINT6-TINT3)} / 6 (1). If the misfire parameter MISB for the opposite cylinder measured at the same tooth position of the ring gear is defined by the formula: MISB = 6 × ΔTINT1 / (TINT9) ³ (2), the misfire parameter MISB finally becomes the following formula. Given in.

MISB = {3 (TINT6-TINT9) +3 (TINT6-TINT3)} / (TINT9) ³ (3)

Incidentally, (TINT9) ^{3 in the} denominator of the equation (2) is a correction amount for eliminating the influence due to the difference in engine speed.

From FIG. 11, a misfire has occurred in the first cylinder, causing a TIN.
As T6 increases, the misfire parameter MISB increases, so it can be determined that misfire has occurred when MISB exceeds a predetermined value. Since the same tooth of the ring gear is used in the misfire determination using the MISB, it has the characteristic that it is not affected by the shape variation of the ring gear.

However, when the first cylinder and the fourth cylinder both misfire continuously, TINT3, TINT6,
Since all of TINT9 are equally large, ΔT
Since INT1≈0 (that is, MISB≈0) and misfire cannot be determined, it is necessary to consider other misfire parameters.

Therefore, as shown in FIG. 12, the time increase ΔTINT2 due to misfire is calculated using the measured value of the sixth cylinder, which is one cylinder before the first cylinder, which is the misfire cylinder. Δ
TINT2 is also calculated by the graphic processing according to the following formula: ΔTINT2 = {5 (TINT6-TINT7) + (TINT6-TINT1)} / 6 (4), so that the same ring gear as in the first cylinder and the sixth cylinder When the misfire parameter MISA when it is not measured at the tooth position is defined by the formula MISA = 6 × ΔTINT1 / (TINT9) ³ (5), the misfire parameter MISA is finally given by the following formula.

MISA = {5 (TINT6-TINT7) + (TINT6-TINT1)} / (TINT9) ³ (6)

According to the misfire parameter MISA thus obtained, even when the opposite cylinders measured at the same tooth position of the ring gear, such as the first cylinder and the fourth cylinder, are continuously misfired together, Can be judged to be a misfire because the value exceeds a predetermined value.

By the way, each of the sections a, b, and c corresponds to a predetermined number of teeth of the ring gear, and the time when the predetermined number of teeth is counted by the magnetic pickup is used as a measured value TINT. Therefore, depending on the accuracy of the ring gear, the measured values in the respective sections a, b, and c are not the same while the crankshaft is rotating at a constant speed, which causes an error in the misfire parameter MISA, which causes a misdiagnosis. Sometimes.

In view of this, Japanese Patent Laid-Open No. 4-101071 introduces a learning value of ring gear accuracy, and permits misfire determination when the learning value converges.

[0015]

By the way, in the device of the above-mentioned Japanese Patent Laid-Open No. 4-101071, when the learning value is not calculated during the current operation, the learning stored in the backup RAM during the previous operation. The value is read out and used as it is for diagnosis. However, in this device, after switching the ignition key from off to on, 1
A predetermined number of ring gears P from the input of the Ref signal for the No. cylinder.
Since the TINT measurement is started with reference to the time point when the os signal (a pulse obtained by the magnetic pickup) is counted, there is a deviation from the previous operation of the initial position of the Ref signal for the first cylinder. In this case, the tooth position of the TINT measurement ring gear during the current operation may be significantly different from that during the previous operation.

For example, the Ref signal for the No. 1 cylinder is the same as the Ref signal for the first cylinder shown in (a) and (b) of FIG.
If the current operating time also rises at the position shown in (a) of FIG. 13, the learned value stored in the backup RAM during the previous operating time gives a highly accurate value to the measured value TINT during the current operating time. .

However, the Ref signal for No. 1 cylinder obtained by the crank angle sensor provided on the camshaft has a relatively large variation of ± several degrees in crank angle at the rising position thereof. Thirteen
As shown in (c) and (d), the rise of the Ref signal for the first cylinder is delayed, and the start of TINT measurement may deviate by one tooth of the ring gear.

In this way, the rise of the Ref signal for the first cylinder is delayed from the previous operation, so that TINT
If the tooth position for measurement is deviated by one tooth, the learned value stored in the backup RAM during the previous operation will no longer give an accurate value to the measured value TINT during the current operation, resulting in an error. There is a possibility that misdiagnosis may occur with the learned value.

The effect is great even for one tooth. Since the rotation fluctuation due to misfire in the high rotation region is on the order of 0.1%, even if the tooth position of the ring gear is shifted by one tooth in the high rotation region, erroneous diagnosis will surely occur. The order of 0.1% is for 6 cylinders, but if the number of cylinders further increases, this order will become smaller and the probability of erroneous diagnosis will increase.

Therefore, according to the present invention, it is possible to prevent erroneous diagnosis by checking whether or not the learning value backed up during the previous operation can be used as it is for the diagnosis during the current operation each time the operation is started. To aim.

[0021]

The first invention, as shown in FIG. 14, is a means 21 for measuring the time required for a predetermined crank angle section corresponding to the combustion stroke for each cylinder, and a cylinder 21 having this measured value. Means 22 for calculating a learned value for correcting the variation of the above, a backup memory 23 for storing the learned value even after the engine is stopped, and a backup memory 23 before the operation of the learned value at the time of the present operation. Means 24 for making a misfire determination based on the variation of the measured value at the time of the current operation with the learned value present, and the predetermined crank angle section used for the measurement at the same position (or the same phase) as the previous operation. The means 25 for determining whether or not each operation is performed, and the misfire determination is performed when the predetermined crank angle section used for measurement is not at the same position as the previous operation based on the determination result. It provided with means 26 for locking.

According to a second aspect of the present invention, in the first aspect of the present invention, when the predetermined crank angle section used for measurement is not at the same position as in the previous operation, the learning value is returned to the initial value. The learning value is calculated, the learning value is converged, the prohibition of the misfire determination is released, and the misfire determination is performed using the converged learning value.

A third aspect of the present invention is the same as the first or second aspect, wherein the position determining means 25 is, as shown in FIG.
A sensor 31 that outputs a reference position signal (Ref signal) of the crank angle of each cylinder and a sensor 32 that outputs a crank angle signal (Pos signal) corresponding to the tooth width of the ring gear.
And means 33 for measuring the number of crank angle signals corresponding to the tooth width of the ring gear from the input of the reference signal of a specific cylinder (for example, the first cylinder) to the measurement start point of the predetermined crank angle section, When the difference between the measured number of crank angle signals and the value stored in the backup memory 34 is within a predetermined range, the predetermined crank angle section used for the measurement is at the same position as the previous operation, Further, when the difference between the two is not within the predetermined range, the means 35 for determining that the predetermined crank angle section used for the measurement is not at the same position as the previous operation, and the predetermined crank angle section used for the measurement based on this determination result When it is in the same position as when it is in operation, the measured number is stored in the backup memory 34.
Means 36 for updating as the value of.

In a fourth aspect based on the third aspect, the sensor 31 for outputting the reference position signal of the crank angle of each of the cylinders is driven by a crankshaft through a winding transmission device (for example, a timing chain). It is provided on a shaft (for example, a camshaft), and the number of crank angle signals from the input of the reference signal of a specific cylinder to the measurement start point of the predetermined crank angle section is measured during acceleration.

In a fifth aspect based on the third aspect, the crankshaft drives a shaft different from the crankshaft via a timing chain and is driven by receiving hydraulic pressure from an engine-driven hydraulic pump. While the timing chain is stretched by a chain tensioner, a sensor 31 that outputs a reference position signal of the crank angle of each cylinder is provided on the shaft different from the crankshaft, and the predetermined signal is input from the input of the reference signal of a specific cylinder. The crank angle signal number up to the measurement start point in the crank angle section is measured in a predetermined rotation range where the hydraulic pressure of the hydraulic pump increases.

[0026]

[Operation] When the learning value is not calculated during the current operation, the learning value stored in the backup memory during the previous operation is read and used as it is for the misfire determination. If is not in the same position as the previous operation, the learned value stored in the backup memory will not give a highly accurate value to the measured value of the current operation, and an incorrect learning value will cause a false diagnosis. Can occur. At this time (that is, when the predetermined crank angle section used for measurement is not at the same position as in the previous operation), according to the first invention, the learning value stored in the backup memory during the previous operation is used. Since the misfire determination is prohibited, the misdiagnosis due to the use of the learned value with an error can be avoided.

Even when the predetermined crank angle section used for measurement is not at the same position as in the previous operation, when the learning value is calculated again during the current operation and the learned value converges, the predetermined value used for the measurement during the current operation Since the learned value after the convergence accurately corresponds to the crank angle section of, by performing the misfire determination using the learned value after the re-learning according to the second invention, Opportunities for diagnosis can be increased without causing misdiagnosis.

According to the third aspect of the present invention, when the difference between the number of crank angle signal measurements and the value stored in the backup memory during the previous operation is not within the predetermined range, the predetermined crank angle section used for measurement is determined during the previous operation. Since it is determined that the measurement start is not at the same position as the above, it is possible to avoid erroneous diagnosis when the measurement start is shifted by one tooth of the ring gear and initialized.

According to the fourth aspect of the invention, when the wrapping transmission device such as the timing chain is most stretched at the time of acceleration,
Since the number of crank angle signals from the input of the reference signal of the specific cylinder to the measurement start point in the predetermined crank angle section is measured, the reference position signal of the specific cylinder is unlikely to be displaced from the initial position, and thus the predetermined position used for the measurement is determined. It is possible to accurately determine whether or not the crank angle section of is in the same position as the previous operation.

When the timing chain is stretched by the chain tensioner driven by receiving the hydraulic pressure supplied from the engine-driven hydraulic pump, the hydraulic pressure does not rise, so in the low rotation range where the timing chain cannot be stretched, The reference position signal of the specific cylinder may deviate from the initial position, and an error may occur in the number of measured crank angle signals from the input of the reference signal of the specific cylinder to the measurement start point in a predetermined crank angle section. In the invention of 5, the sensor for outputting the reference position signal of the crank angle of each cylinder is provided on another shaft driven through the timing chain, and the measurement of a predetermined crank angle section is started from the input of the reference signal of the specific cylinder. Since the number of crank angle signals up to the point is measured in a predetermined rotation range where the hydraulic pressure of the hydraulic pump increases, Signal hardly occurs deviation in the initial position, the thus never for errors in counting.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 denotes an engine body, 2 denotes a crankshaft, and 4 denotes a ring gear formed on the outer periphery of a flywheel 3 at the end of the crankshaft. A magnetic pickup 5 composed of an iron core and a coil is installed facing the teeth of the ring gear 4, and a crankshaft 2 is provided.
When the gear rotates, the teeth intermittently interrupt the magnetic field generated in the iron core of the magnetic pickup 5, so that a magnetic force change occurs in the coil of the magnetic pickup 5 and an alternating current is induced. This AC signal is shaped into a waveform in the control unit 7 and converted into a rectangular wave ON / OFF pulse (ring gear Pos signal), which is used as a crank angle signal.

A known crank angle sensor 6 is provided on a camshaft (not shown) driven by the crankshaft 2, and the Ref signal (reference position signal) and Pos signal (1 ° signal) from this sensor 6 are also provided. It is sent to the control unit 7.

In the control unit 7, a predetermined number C from the input of the Ref signal for the first cylinder of the crank angle sensor 6
With reference to the time point when the ring gear Pos signal of RING1 is counted, as shown in FIG. 2, the time TINT required for a predetermined angular section of the crankshaft 2 is sampled three times per one revolution of the crankshaft, and the sampled value is obtained. Use to determine misfire. However, FIG. 2 is for a V6 cylinder engine, and the ignition sequence is 1-2-3-
4-5-6, combustion strokes of the first cylinder and the fourth cylinder in the section a, the second cylinder and the fifth cylinder in the section b, and the third cylinder and the sixth cylinder in the section c. Corresponding to.

In this case, when the ring gear 3 has tooth density during manufacture or tooth wear due to deterioration over time, even if the crankshaft rotates at a constant speed, as shown in FIG. The waveform has a TINT value that varies in each section b and c. Since the measurement of TINT is performed by counting the ring gear Pos signal generated corresponding to each tooth of the ring gear 4 in detail, the tooth row in the section a is, for example, coarser than the specified value, and the tooth row in the section b is also larger. Is denser than the specified value, even if the ring gear Pos signals of the same number as the specified value are counted, the TIN in the section a
The value of T becomes larger than the specified value, and TINT in section b
The value of is smaller than the specified value. When there is a rotation fluctuation due to a factor other than misfire overlapping with such a waveform shown in FIG. 3, the apparent rotation fluctuation (see the solid line in the upper part of FIG. 4) is larger than the actual rotation fluctuation as shown in FIG. In other words, a misfire may be erroneously determined.

In order to deal with this, a learning value of the ring gear accuracy is introduced, and the measured value TINT is corrected with this.

In this case, it is known from experiments and theoretical analyzes that the time increase ΔTINT of TINT due to misfire is inversely proportional to the cube of the engine speed. On the contrary,
Since the time increase ΔTINT due to the ring gear accuracy is inversely proportional to the engine speed, as shown in FIG. 5, the effect of the gear accuracy increases as the rotation speed increases. Further, even in the high rotation speed range, when the load is low, the rotation fluctuation due to the misfire and the variation in the torque between the cylinders is small.

The flowchart of FIG. 6 shows learning of ring gear accuracy. In step 1, it is determined whether or not the learning condition is satisfied. When the engine is in the high rotation and low load region and fuel is not being cut and there is no lean spike, it is determined that the learning condition is satisfied and the process proceeds to step 2.
The measured value TINT is sampled over one revolution of the crankshaft. Measured values from newest to TINT
It is stored in the memory as 1, TINT2, and TINT3.

In step 3, the average value of the measured values (TINT1, TINT2, TINT3) for one revolution of the crankshaft is calculated, and this average measured value and TINT1, TIN are calculated.
In step 7, the learning value of the ring gear accuracy is calculated using the measured values of T2 and TINT3. The learning value calculation formula is: a section learning value (new) ← a section learning value (old)-{(a section measured value x a section learning value (old) -average measured value) / average measured value} x learning speed Coefficient (7a) b section learning value (new) ← b section learning value (old)-{(b section measurement value x b section learning value (old) -average measurement value) / average measurement value} x learning speed coefficient ... (7b) c section learning value (new) ← c section learning value (old)-{(c section measured value x c section learning value (old) -average measured value) / average measured value} x learning speed coefficient (7c) ) However, learning value (new): current learning value learning value (old): previous learning value. This is to calculate the learning value in a direction that eliminates the difference between the average measured value per engine revolution and the actual measured value of each section of a, b, c. When the calculation is actually performed when the average value is 110% (learning speed coefficient is 0.5), the a section learning value (initial value is 100%) is as follows: 1st time: 100- (110 × 100− 100) × 0.5 = 95% Second time: 95− (110 × 95−100) × 0.5 = 92.75% Third time: 92.75− (110 × 92.75−100) × 0.5 = 91.736% A few times: = 90.909% (see FIG. 7), and it can be seen that the value obtained by multiplying the a section learning value by the a section measurement value converges to the average measurement value of a, b, and c. .

In step 5 of FIG. 6, the current learning value and the previous learning value are compared, and if the difference is within the allowable value, it is determined that the learning value has converged, and in step 6, each of the three learning values is learned. Save the value in memory. After the learning is completed in this way, the a section learning value stored in the memory at the time of misfire diagnosis is set to the a section measured value, the b section learning value is set to the b section measured value, and the c section learning value is set to c. By using the values obtained by multiplying the section measurement values, it is possible to avoid erroneous diagnosis due to ring gear accuracy.

Incidentally, step 11 not explained in FIG.
Will be described later.

The flowchart of FIG. 8 is for making a misfire diagnosis. As will be described later in step 31, in step 21, it is checked whether the condition is a diagnostic condition. The diagnostic conditions are that the fuel cut is not in progress and that the water temperature is above a specified value.

If it is a diagnostic condition, step 22 in FIG.
Measured value TIN of the time required for each section of a, b, and c shown in
Sample T. Put the latest value in TINT1,
By shifting the old values in order, nine samples (TINT1, TINT2, ..., TINT9) from the latest one are sampled.

In step 23, the section learning values of a, b, and c are read from the memory, and the values obtained by multiplying these by the corresponding measurement values are used to calculate the misfire parameter MISB of the above equation (3) and the above equation (6). And the misfire parameter MISA of each cylinder is calculated in step 24.

At step 25, it is checked whether the calculation of misfire parameters has been completed for all cylinders.
If it has ended, the routine proceeds to step 26, where failure determination is performed for each cylinder using the misfire parameter. This failure determination is described in detail in Japanese Patent Laid-Open No. 4-113244, but since it is not directly related to the present invention, its description is omitted.

The learning of the ring gear up to this point is the same as in Japanese Patent Application Laid-Open No. 4-101071, and the diagnosis is the same as in Japanese Patent Application Laid-Open No. 4-113244.

By the way, when the learning value is not calculated yet during the current operation, the backup RA during the previous operation
If the learning value stored in M is read and used as it is for diagnosis, the tooth position of the ring gear for TINT measurement differs greatly from that during the previous operation due to variations in the initial position of the No. 1 cylinder Ref signal. In this case, the learned value stored in the backup RAM does not give a highly accurate value to the measured value TINT during the current operation, and there is a possibility that the learned value with an error causes erroneous diagnosis.

To deal with this, the present invention checks whether or not the learned value backed up during the previous operation can be used as it is for the diagnosis during the present operation each time the operation is started. Specifically, the flowchart shown in FIG. 9 is newly provided, and step 3 in FIG.
1 and step 11 in FIG. 6 are added.

First, the flowchart of FIG.
This is to confirm whether the tooth position of the ring gear for measurement is the same between the previous operation and the current operation.

In steps 41 and 42 of FIG. 9, the following condition engine rotation speed N is not less than a predetermined value (step 41), and the increase ΔN in rotation speed per predetermined time is not less than a predetermined value (step 42). If both conditions are satisfied, the step 43 and the subsequent steps are performed each time the Ref signal for the first cylinder is input (that is, once every two engine revolutions). As shown in FIG. 10, the conditions for and are satisfied by the crank sprocket 1
1 is a condition in which the timing chain 13 that hangs around the cam sprocket 12 is tight. If the hydraulic pressure to the chain tensioner 14 driven by the hydraulic pressure supplied from the engine-driven hydraulic pump is sufficiently high (that is, the rotation speed is a predetermined value or more), and the timing chain 13 is taut during acceleration, As a result, the deviation of the initial position of the Ref signal for the first cylinder obtained by the crank angle sensor 6 can be eliminated.

At step 43, the ring gear Pos signal number CRING1 from the input of the Ref signal for the first cylinder to the TINT measurement start point is measured, and at step 44, the cumulative number NCRING is compared with a predetermined value. The total number of times is 0 when the ignition key is turned on (started).
Since the initial setting is performed, the process proceeds to steps 45 and 46 until the number of times of integration reaches a predetermined value or more. In steps 45 and 46, the above-mentioned CRING1 is added to the integrated value SCRING,
The cumulative number of times NCRING is incremented by 1. The integrated value SCRING is also initialized to 0 at the timing when the ignition key is turned on.

When the cumulative number of times NCRING becomes equal to or greater than the predetermined value by the repetition of step 46, step 4
The processing shifts from step 4 to step 47 and thereafter.

At step 47, the average value CAVE of the integrated value SCRING is calculated, this average value CAVE is compared with the previous backup value CAVEBU, and either one of the following 1) and 2) is performed. After this processing, the tooth position confirmation control shown in FIG. 9 is not performed until the ignition key is turned off.

1) Difference between average value and backup value (CA
VE-CAVEBU) in step 48, 49 judgment value R
Compared with GOK (RGOK> 0), -RGOK ≦ CAV
If E-CAVEBU <RGOK, it is determined that the tooth position of the TINT measurement ring gear is the same as that at the time of TINT measurement during the previous operation. In this case, steps 50, 51
Set the learning value use permission flag (initially set to "0" at the timing of turning on the ignition key) to "1" and move the average value CAVE to CAVEBU for the tooth position confirmation control at the next operation. Back up R
Save it in AM.

2) When the above 1) does not apply, all learning values are cleared (that is, returned to 100% of the initial value) in steps 52 and 53 in order to redo the ring gear learning, and the tooth position at the time of the next operation is set. At this time as well, the average value CAVE is transferred to CAVEBU for confirmation control.

Next, in the flowchart of the diagnosis shown in FIG. 8, step 31 is added, and only when the use permission flag of the learning value is "1", the diagnosis after step 21 can be proceeded. The use permission flag of the learning value becomes "1" in the case of 1) above, and the backup RAM at the time of the previous operation is provided on condition that the tooth position of the TINT measurement ring gear is the same as that at the time of the previous operation. The diagnosis is made using the learning value stored in.

On the other hand, in the case of 2) above, it is not possible to proceed to step 21 and thereafter. T as in 2) above
If the tooth position of the INT measurement ring gear is not the same during the previous operation and the current operation, a false diagnosis may occur when the learning value stored in the backup RAM during the previous operation is used. Before confirming that the tooth position of the measurement ring gear is the same between the previous operation and the current operation, it is necessary to prevent it from entering the diagnosis.
It is possible to avoid erroneous diagnosis when there is a deviation of the initial position of the Ref signal for the No. cylinder from the previous operation.

Next, step 11 is added to the flowchart of the ring gear learning shown in FIG. 2) above
In this case, since all the learning values are cleared, the ring gear learning is performed again in FIG. 6, and at the timing when the learning values converge, the learning value use permission flag is set to “1” in step 11. I have to. By setting this flag to “1”, even after re-learning, FIG.
In, it is possible to proceed to step 21 and subsequent steps. That is, also in the case of 2) above, when learning is performed again for the tooth position of the TINT measurement ring gear during the current operation and the learned value converges, the learned value after the convergence is the TINT during the current operation. Since it accurately corresponds to the tooth position of the measuring ring gear, after the re-learning, the diagnosis can be performed again using the learned value after the re-learning, which causes a false diagnosis. Without increasing the chance of diagnosis.

In this way, after confirming that the tooth position of the ring gear for TINT measurement is the same between the previous operation and the current operation, the tooth position of the ring gear for TINT measurement is changed to the previous operation. If it is not the same at the time of this operation and at the time of this time's operation, re-learning is made to correspond to the tooth position of the ring gear for TINT measurement at this time and the learned value so that the diagnosis can be entered. Even if there is a variation in the initial position of the Ref signal, or if there is deformation of the ring gear or tooth jump between the input of the Ref signal for the first cylinder and the measurement start point of TINT, erroneous diagnosis can be avoided.

[0059]

According to the first aspect of the present invention, the learning that has an error occurs when the learned value stored in the backup memory during the previous operation does not give an accurate value to the measured value during the current operation. Misdiagnosis caused by using the value can be avoided.

In the second aspect of the invention, even when the predetermined crank angle section used for measurement is not at the same position as in the previous operation,
Opportunities for diagnosis can be increased without causing misdiagnosis.

According to the third aspect of the present invention, it is possible to avoid erroneous diagnosis when there is a deviation of one tooth of the ring gear between the input of the reference signal of the specific cylinder and the measurement start point in the predetermined crank angle section.

In the fourth aspect of the invention, the reference position signal of the specific cylinder is unlikely to be displaced from the initial position, whereby it is possible to accurately determine whether or not the predetermined crank angle section used for measurement is in the same position as in the previous operation. It can be carried out.

In the fifth aspect of the invention, even when the timing chain is stretched by the chain tensioner driven by receiving the hydraulic pressure supplied from the engine-driven hydraulic pump, the reference position signal of the specific cylinder indicates the initial position. The deviation is unlikely to occur, and therefore the measurement number does not have an error.

[Brief description of drawings]

FIG. 1 is a control system diagram of an embodiment.

FIG. 2 is a diagram for explaining each measurement section of a, b, and c.

FIG. 3 is an explanatory diagram of a measurement error.

FIG. 4 is an explanatory diagram of a measurement error.

FIG. 5 is an explanatory diagram showing the influence of misfire on rotation and the influence of gear accuracy on rotation.

FIG. 6 is a flowchart for explaining ring gear learning.

FIG. 7 is a waveform diagram showing convergence of learning values.

FIG. 8 is a flowchart for explaining diagnosis.

FIG. 9 is a flowchart for explaining confirmation control of a TINT measurement ring gear tooth position.

FIG. 10 is a layout diagram of a timing chain.

FIG. 11 is a waveform diagram for explaining misfire determination in the conventional example.

FIG. 12 is a waveform diagram for explaining misfire determination in the conventional example.

FIG. 13 is a waveform diagram for explaining the operation of the conventional example.

FIG. 14 is a diagram corresponding to claims of the first invention.

FIG. 15 is a diagram corresponding to the claim of the third invention.

[Explanation of symbols]

 1 Engine Main Body 2 Crank Shaft 4 Ring Gear 5 Magnetic Pickup (Crank Angle Sensor) 6 Crank Angle Sensor (Reference Position Sensor) 7 Control Unit 21 Time Measuring Means 22 Learning Value Calculating Means 23 Backup Memory 24 Misfire Determining Means 25 Position Determining Means 26 Misfire determination prohibiting means 31 Reference position sensor 32 Crank angle sensor 33 Crank angle signal number measuring means 34 Backup memory 35 Judging means 36 Backup memory value updating means

Claims (5)

[Claims] 1. A means for measuring the time required for a predetermined crank angle section corresponding to a combustion stroke for each cylinder, a means for calculating a learning value for correcting the variation of the measured value for each cylinder, and the learning value. Is stored even after the engine is stopped, and before the calculation of the learning value during the current operation, the learned value stored in the backup memory is used to correct the measured value during the current operation. And a means for determining whether or not the predetermined crank angle section used for the measurement is in the same position as in the previous operation, and a predetermined crank angle section used for the measurement in the previous operation based on the determination result. And a means for prohibiting the misfire determination when the engine is not in the same position as the above. 2. If the predetermined crank angle section used for the measurement is not at the same position as the previous operation based on the determination result,
The calculation of the learning value is performed by returning the learning value to the initial value, the prohibition of the misfire determination is canceled after the learning value is converged, and the misfire determination is performed using the converged learning value. The engine misfire diagnosis device according to claim 1, which is characterized in that. 3. The position determining means includes a sensor that outputs a reference position signal of a crank angle of each cylinder, and a sensor that outputs a crank angle signal corresponding to a tooth width of a ring gear.
Means for measuring the number of crank angle signals corresponding to the tooth width of the ring gear from the input of the reference signal of a specific cylinder to the measurement start point in the predetermined crank angle section, the number of crank angle signals measured and a backup memory When the difference between the two is within a predetermined range by comparison with the value stored in, if the predetermined crank angle section used for the measurement is at the same position as the previous operation, the difference between the two is not within the predetermined range. When the predetermined crank angle section used for the measurement is not at the same position as the previous operation, and the predetermined crank angle section used for the measurement is at the same position as the previous operation based on the result of the determination. 3. The engine misfire diagnosis device according to claim 1 or 2, further comprising: means for updating as a value of the backup memory. 4. A sensor for outputting a reference position signal of the crank angle of each cylinder is provided on a shaft driven by a crankshaft via a winding transmission device, and the predetermined signal is input from the input of the reference signal of a specific cylinder. The engine misfire diagnosis device according to claim 3, wherein the number of crank angle signals up to the measurement start point in the crank angle section is measured during acceleration. 5. The crankshaft drives a shaft different from the crankshaft via a timing chain, and the timing chain is stretched by a chain tensioner driven by receiving hydraulic pressure from an engine-driven hydraulic pump. A sensor for outputting the reference position signal of the crank angle of each cylinder is provided on the shaft different from the crankshaft, and the crank from the input of the reference signal of the specific cylinder to the measurement start point of the predetermined crank angle section The engine misfire diagnosis device according to claim 3, wherein the number of angle signals is measured in a predetermined rotation range in which the hydraulic pressure of the hydraulic pump increases.