JPH04104033A - Detecting method for flame failure of internal combustion engine - Google Patents

Abstract

PURPOSE:To perform highly reliable detection of misfire by obtaining the pressure data in an explosion stroke under the state wherein the effect of the offset component of a pressure sensor is removed, and comparing the data with a threshold value. CONSTITUTION:Internal pressures P1' and P2' in cylinders at the specified timing before ignition are detected. Then, an ECU 14 computes the offset component alphaof a pressure sensor based on the pressures P1' and P2'. Then, the ECU 14 makes an ignition plug 3 discharge at the specified timing in the vicinity of a top dead point. Inner pressure P3' in the cylinder at the specified time in the explosion stroke is detected. Then, pressure data beta in the explosion stroke are obtained based on the component alpha and the pressure P3'. A threshold value TH for accurately judging the presence or absence of the explosion is computed with respect to the values of the data beta. The data beta and the threshold value are compared. When the data beta are less than the threshold value TH, it is judged that the cylinder is in the misfire state. A misfire flag for that cylinder is specified. Therefore, the burning state is not erroneously detected, and the highly reliable, highly accurate misfire detection is performed all the time.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for detecting a misfire in an internal combustion engine based on the in-cylinder pressure during the explosion stroke after ignition, and in particular, The present invention provides a misfire detection method for an internal combustion engine that improves reliability by removing an offset component of a pressure sensor based on the cylinder pressure at a point.

[Prior Art] Generally, an internal combustion engine used in a gasoline engine for an automobile or the like is driven by a plurality of cylinders (for example, four cylinders), each with four cycles of intake, compression, explosion, and exhaust. In such an internal combustion engine, calculations are performed electronically by a microcomputer in order to optimally control the ignition timing by the igniter and the fuel injection order by the injector for each cylinder.

Therefore, in addition to various operating conditions and operating states, the microcomputer takes in a reference position signal for each cylinder synchronized with the rotation of the internal combustion engine, a cylinder identification signal corresponding to a specific cylinder, etc., and receives the operating position ( crank angle) and performs control at the optimal timing. Standard position! A rotation signal generator that detects the rotation of the camshaft or crankshaft of the internal combustion engine and generates a synchronization signal is used as a means for generating the signal and the cylinder identification signal.

In general, when controlling the ignition of each of the five cylinders, it is necessary to combust the air-fuel mixture compressed by the piston using the spark from the ignition plug, but depending on the condition of the fuel, spark plug, etc., combustion may not be possible in the ignition-controlled cylinder. . If such a situation occurs, there is a risk that an abnormal load will be applied to other cylinders, damaging the engine, and causing various problems due to gas leakage.

Therefore, in order to ensure the safety of the engine, it is necessary to detect whether combustion has occurred reliably in each cylinder at each ignition cycle. For this reason, devices have been proposed that detect the cylinder pressure during the explosion stroke after one ignition to determine the combustion state or misfire state.

FIG. 7 is a configuration diagram showing a general misfire detection device for internal combustion engines.

In the figure, (1) is the cylinder that drives the internal combustion engine,
A combustion chamber (2), a spark plug (3) provided in the combustion chamber (2), a piston (4) driven by the explosion of the mixed fuel gas in the combustion chamber (2), and supplying the mixed fuel gas. an intake section (5) for discharging gas after fuel; and an exhaust section (6) for discharging gas after fuel.
), an intake valve (7) that controls opening and closing between the intake section (5) and the combustion chamber (2), and an exhaust valve (8) that controls opening and closing between the combustion chamber (2) and the exhaust section (6). ).

The spark plug (3) has a center electrode connected to an ignition coil (described later) and a ground electrode facing the center electrode. Further, for example, in the case of a four-cylinder engine, there are four cylinders similar to the cylinder (1), and 6 (9) is an injector for supplying fuel provided in the intake part (5). A predetermined amount of mixed fuel gas is supplied according to the amount of air depending on the throttle opening of the accelerator.

(2a) is an orifice provided on the cylinder wall of the combustion chamber (2), and (10) is an orifice provided in the cylinder wall of the combustion chamber (2).
) is a pressure sensor that detects the cylinder pressure, (11) is an ignition coil whose output terminal of the secondary winding is connected to the center electrode of the spark plug (3), and (12) is the input of the ignition coil (11). A power supply (13) is an ignition device connected to the output terminal of the negative winding of the ignition coil (11).

(14) is a microcomputer (hereinafter referred to as ECtJ) that controls the intake valve (7), exhaust valve (8), injector (9), ignition device (13), etc., and the cylinder (
1) It has a threshold generation means for generating the misfire judgment standard (threshold) and various calculation units, and it is equipped with a reference position signal representing the cylinder state and signals representing various operating states, etc., as well as the cylinder pressure from the pressure sensor (lO). It incorporates P.

Here, in order to capture the cylinder pressure P at a predetermined time during the explosion stroke, a rotation angle sensor (not shown) for generating a reference position signal corresponding to the crank angle, for example, is equipped with a rotation angle sensor (not shown) at a predetermined time during the explosion stroke. A slit corresponding to this is formed. This predetermined timing depends on the cylinder pressure P depending on the presence or absence of an explosion.
The crank angle that causes a large difference in
It is set at an arbitrary point within the range of 0° (10' to 90° after TDC).

Next, the operation of the misfire detection device between internal combustion engines shown in FIG. 7 will be explained.

As mentioned above, in the combustion chamber (2), the piston (4
) takes place during two reciprocating movements, and the ECU (14) controls the amount of fuel supplied by the injector (9) during the intake stroke and the spark plug (3) during the explosion stroke. ignition timing etc. are optimally controlled according to operating conditions.

That is, when the intake valve 7) is opened and mixed fuel gas is drawn into the combustion chamber (2) from the intake section (5), the amount of fuel gas supplied to the intake section (5) depends on the opening degree of the throttle by accelerator operation. The amount of fuel supplied from the injector (9) is controlled together with the amount of air supplied.

Further, after compressing the mixed fuel gas in the combustion chamber (2), the ignition device (13) is driven at a predetermined timing to intermittently energize the negative winding of the ignition coil (11). This allows the spark plug (3) to be connected from the secondary winding of the ignition coil (11) to the spark plug (3).
A high voltage of negative polarity is applied to the center electrode of the combustion chamber (2), sparks are generated due to discharge between it and the ground electrode, and an explosion occurs within the combustion chamber (2). Usually, the ignition timing is at a crank angle of 0°, that is, near TDC (top dead center).

When an explosion (combustion) occurs due to discharge of the spark plug (3), the cylinder pressure P in the combustion chamber (2) detected by the pressure sensor (10) increases; however, if no explosion occurs due to a misfire, the cylinder pressure increases. P has a low value.

Therefore, the E CU (14) takes in the cylinder pressure P at a predetermined time during the explosion stroke, generates a threshold for misfire determination from the threshold generation means, and compares the cylinder pressure P with the threshold.

Then, if the cylinder pressure P is below the threshold,
The misfire state of a cylinder is determined and a misfire flag is set for that cylinder.

However, since the pressure sensor (10) includes an offset component, if a misfire condition is determined only based on the comparison result between the cylinder pressure P and the threshold, for example, the level of the cylinder pressure P may exceed the threshold due to the offset component. There is a possibility that it will be exceeded. For this reason, it may be determined that combustion has occurred normally even though combustion has not actually occurred, which may lead to damage to the engine as described above.

[Problem to be Solved by the Invention 1] As described above, in the conventional misfire detection method for an internal combustion engine, the combustion state is determined when the cylinder pressure P exceeds the threshold. When these are superimposed, it is determined that combustion has occurred even though there has been a misfire, making it difficult to detect a misfire with high reliability.

This invention was made in order to solve the above-mentioned problems, and is capable of detecting a misfire in an internal combustion engine without impairing reliability even when off-cellar 1 to 1 components of a pressure sensor are superimposed on a detected value of cylinder pressure. The purpose is to obtain a method.

[Means for Solving the Problems] A misfire detection method for an internal combustion engine according to a first aspect of the present invention includes detecting first and second cylinder pressures at first and second predetermined times during a compression stroke. a step of calculating an offset component of the pressure sensor based on the first and second in-cylinder pressures; a step of detecting the third in-cylinder pressure at a third predetermined time during the explosion stroke; determining the explosion stroke pressure information based on the component and the third cylinder pressure; calculating a threshold for the explosion stroke pressure information; comparing the explosion stroke pressure information with the threshold; The present invention includes a step of determining whether a cylinder misfires in the following cases.

Further, a misfire detection method for an internal combustion engine according to a second aspect of the present invention includes the steps of: detecting first and second in-cylinder pressures at first and second predetermined times during a compression stroke; a step of calculating an offset component of the pressure sensor based on the second in-cylinder pressure; a step of calculating an integral value of the in-cylinder pressure from the second predetermined time to a third predetermined time during the explosion stroke; a step of correcting the integral value based on the component; a step of calculating a threshold for the integral value; a step of comparing the corrected integral value with the threshold; The method also includes a step of determining a misfire condition.

Further, a misfire detection method for an internal combustion engine according to a third aspect of the present invention includes the steps of: detecting first and second in-cylinder pressures at first and second predetermined times during a compression stroke; calculating a third in-cylinder pressure at a third predetermined time during the explosion stroke based on the second in-cylinder pressure;
a step of detecting a third in-cylinder pressure at a third predetermined time; a step of calculating a deviation between a calculated value and a detected value of the third in-cylinder pressure; a step of calculating a threshold for the deviation; and a step of determining whether the cylinder has misfired if the deviation is less than a threshold.

[Operation] In this invention, based on the in-cylinder pressure at the first and second predetermined times of the compression stroke, the third predetermined time during the explosion stroke is determined with the influence of the offset component of the pressure sensor removed. Determine the explosion stroke pressure information 3 corresponding to the cylinder pressure of
This explosion stroke pressure information is compared with a threshold, and if it is below the threshold, a misfire is detected.

[Embodiment 2] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1st
The figure is a flowchart showing an embodiment of the first invention at this stage, and FIG. 2 is a waveform diagram analytically showing each step in FIG.

In Fig. 2, contact wheel θ is the crank angle position, vertical axis P is the cylinder pressure, α is the offset component of the pressure sensor, θ1 to θ
, are the first to third predetermined periods, Pl' to P,' are the first to third cylinder pressures detected at the first to third predetermined periods, and TDC is the piston connected to the crankshaft ( 4) is the top dead center.

Incidentally, the apparatus to which the embodiment of the present invention is applied is as shown in FIG. 7, and it is only necessary that a part of the calculation program in the ECU (14) be changed. In this case, ECU
('14) consists of an operating state detection section that determines the operating state based on a reference position signal and an operating state signal, a Threnjord calculation section that calculates a threshold based on the operating state, and a calculation section that calculates explosion stroke pressure information. Contains.

First, in the compression stroke before ignition, at a predetermined timing,
That is, first and second cylinder pressures P,' and P2' at first and second predetermined times are detected (step S1
).

Here, the first and second predetermined times θ1 and θ2 can be set at any two points during the compression stroke, but for example,
The crank angle may be set at a time when the crank angle is B75° (75° before TDC) and when the crank angle is B5° (5° before TDC).

Next, the E CU (14) calculates the offset component α of the pressure sensor based on the first and second cylinder pressures Pl' and P2' (step s2).

Specifically, since the volumes V1 and V2 of the combustion chamber (2) at the first and second predetermined times θ and θ2 are known in advance, they are determined as follows based on Boyle's law. That is, from (P+'-12)VI=(P2'-12)Vl, P+'・Vl-P2''V2=(Vl-Vl)+2, so the offset component α is α=(P,'V , -P2''Vl)/(Vl-Vl)...
・Represented by ■.

Next, the E CU (14) discharges the spark plug (3) at a predetermined timing near TDC based on the reference position signal indicating the crank angle for each cylinder, and then discharges the spark plug (3) at a predetermined timing near TDC. The third cylinder pressure P at a predetermined time θ,
c' is detected (step S3).

This third predetermined time θ may be set to about A30°, for example. Therefore, in the case of a normal explosion, the cylinder pressure Px' will be at a large level as shown by the solid line in Figure 2, and in the case of a misfire, it will be at a small level as shown by the one-point value line. .

Next, based on the offset component α and the third in-cylinder pressure P3' obtained from the equation
Z ) Vl (P 3” Q ) Vxl-・■
(Step S4).

Here, since the offset component α has been removed, the explosion stroke pressure information β calculated from equation (2) is independent of variations in the pressure sensor and is a highly reliable value.

If the explosion does not occur normally due to a misfire, the piston (4) simply moves back and forth, so (P2'-α)V2=(P:l'-α)Vyu ・■ holds, and from equation (2), β=0. If a normal explosion occurs, equation 0 does not hold, so β>0.

Therefore, it is necessary to calculate the threshold TH for accurately determining the presence or absence of an explosion with respect to the value of the explosion stroke pressure information β corresponding to the third predetermined time θ. Compare (Step S
6).

If the explosion stroke pressure information β exceeds the threshold TH, it is determined that combustion is normal (step S7), and if the explosion stroke pressure information β is below the threshold TH, it is determined that the cylinder is in a misfire state (step S8). Set a misfire flag.

The above steps S1 to S8 are repeated at each of the first to third predetermined periods θl to θ, and when a misfire occurs in the detection target cylinder, it is immediately detected. At this time, even if the level of the third cylinder pressure P,' changes due to the offset component α, the explosion stroke pressure information β becomes a stable value that hardly changes. Therefore, there is no possibility of erroneously detecting the combustion state, and highly reliable and highly accurate misfire detection is always performed.

In the above embodiment, the explosion stroke pressure information β was obtained based on Boyle's law, but other values (for example, integral values) may be used as the explosion stroke pressure information β' at the six third predetermined times.
may also be used.

The third section is a flowchart showing an embodiment of the second invention of the present invention when the integral value β' is used as the explosion stroke pressure information. They correspond to S4 to S6, respectively, and Sl,
S2, S7 and S8 are the same steps as described above. Also, the fourth diagram is a waveform diagram analytically showing each step in FIG.
' is the same as above.

In this case, after determining the offset component α in steps S1 and S2, the integral value β' of the cylinder pressure P from the second predetermined time θ2 to the third predetermined time θ is calculated (step 513), the offset component Integral value β′ based on α
is corrected (step s4'). Here, it goes without saying that the offset component α can be obtained from the above-mentioned equation (2).

At this time, the integral value β' in step S13 is θ2
The integral formula from to θ, β′=! The integral value β' after correction in step 54' is calculated from β'=iP(θ)dθ−α1θ3−θ21 (2).

The integral value obtained from equation (2) represents the area of the shaded area in FIG. 4, and does not include the offset component α. As is clear from Fig. 4, the cylinder pressure P after TDC
According to
-Dot chain! It can be clearly distinguished from normal conditions because it decreases significantly.

Next, a threshold TH' corresponding to the integral value β' is calculated according to the operating state (step S5').

The corrected integral value β' is compared with the threshold TH' (step S6').

For example, when the rotational speed of the internal combustion engine is high or the load is large, the threshold of the integral value (explosion stroke pressure information) β' increases, so a high threshold TH' is set while referring to a map etc. .

If the corrected integral value β' is less than the threshold TH', the misfire state of the cylinder is determined (step S8), and a misfire flag is set for that cylinder as described above.

Moreover, FIG. 5 is a flowchart diagram showing an embodiment of the third invention of the present invention, in which S4" to S6" correspond to the above-mentioned steps 34 to S6, and S1, S3, S7 and S8 are This is the same step as above. Moreover, FIG. 6 is a waveform diagram analytically showing each step in FIG.
C5θ, ~θ, and P1' to P3' are the same as described above.

In this case, after detecting the first and second cylinder pressures P,' and P2' in step S1, each cylinder pressure Pl'
and 22', the third cylinder pressure P is calculated by calculation.
3'' is calculated (step 512).

That is, focusing on the fact that the waveform of the cylinder pressure P when no misfire occurs is symmetrical with respect to TDC, as shown by the dashed line in FIG.
The calculated value P,'' can be obtained by performing linear interpolation between the time period θ and the third predetermined time θ.

Here, if the difference between the cylinder pressures 21' and P2' is ΔP, the calculated value P, l- of the third cylinder pressure is p, = p
2'-ΔP(θ,-θ,)/(θ,-θ2). However, ΔP=P,'-P.

It is.

Next, in step S3, the third cylinder pressure P is determined.

is detected, and the calculated value 23' of the third cylinder pressure and the detected value P
The deviation β″ from 3″ is calculated from β″−P) P3′ . . . (Step 84″).

According to Equation 0, since the offset component α is not present at all in the deviation β″, the deviation β″ becomes the explosion stroke pressure information from which the offset component α is removed.

Subsequently, after calculating the threshold TI('' for the deviation β'' (step S5''), the deviation β'' is compared with the threshold TH'' (step 56-). Then, if the deviation β'' is less than or equal to the threshold TH'' In step S8), the misfire state of the cylinder is determined and a misfire flag is set for that cylinder.

[Effects of the Invention] As described above, according to the first aspect of the present invention, the step of detecting the first and second in-cylinder pressures at the first and second predetermined times during the compression stroke; and a step of calculating an offset component of the pressure sensor based on the second cylinder pressure, and a step of calculating the offset component of the pressure sensor based on the second cylinder pressure, and
a step of detecting the in-cylinder pressure of the third cylinder; a step of obtaining explosion stroke pressure information based on the offset component and the third in-cylinder pressure; a step of calculating a threshold for the explosion stroke pressure information; and a step of determining the explosion stroke pressure information as the threshold. The offset component of the pressure sensor is determined based on the first and second cylinder pressures during the compression stroke. Since the removed explosion stroke pressure information is obtained and compared with the threshold, internal combustion reliability is not compromised even if the offset component of the pressure sensor is superimposed on the detected value of the cylinder pressure. This has the effect of providing an engine misfire detection method.

Further, according to the second aspect of the present invention, the first
and a step of detecting first and second in-cylinder pressures at a second predetermined time, a step of calculating an offset component of the pressure sensor based on the first and second in-cylinder pressures, and a second predetermined time. a step of calculating the integral value of the cylinder pressure up to a third predetermined time during the explosion stroke; a step of correcting the integral value based on the offset component; a step of calculating a threshold for the integral value; The method includes a step of comparing the integral value with a threshold, and a step of determining a misfire state of the cylinder when the corrected integral value is less than the threshold, based on the first and second cylinder pressures during the compression stroke. Since the explosion stroke pressure information from which the offset component of the pressure sensor has been removed is obtained and this explosion stroke pressure information is compared with the threshold, reliability is maintained even if the offset component of the pressure sensor is superimposed on the detected value of the cylinder pressure. This has the effect of providing a method for detecting a misfire in an internal combustion engine that does not impair the performance of the engine.

Further, a misfire detection method for an internal combustion engine according to a third aspect of the present invention includes the steps of: detecting first and second in-cylinder pressures at first and second predetermined times during a compression stroke; calculating a third in-cylinder pressure at a third predetermined time during the explosion stroke based on the second in-cylinder pressure;
a step of detecting a third in-cylinder pressure at a third predetermined time; a step of calculating a deviation between a calculated value and a detected value of the third in-cylinder pressure; a step of calculating a threshold for the deviation; and a step of determining a misfire state of the cylinder when the deviation is below a threshold, and an offset component of the pressure sensor is removed based on the first and second cylinder internal pressures during the compression stroke. Since the explosion stroke pressure information is obtained and compared with the threshold, the reliability of the internal combustion engine is not compromised even if the offset component of the pressure sensor is superimposed on the detected value of the cylinder pressure. This has the effect of providing a misfire detection method.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an embodiment of the first invention of the present invention, FIG. 2 is a waveform diagram analytically showing each step in FIG. 1, and FIG. 3 is a flowchart showing an embodiment of the first invention of the present invention. 4 is a waveform diagram analytically showing each step in FIG. 3. FIG. 5 is a flowchart diagram showing an embodiment of the third aspect of the present invention. The figure is a waveform diagram analytically showing each step in Fig. 5, and Fig. 7 is a configuration diagram showing a general misfire detection device for an internal combustion engine. (14)...ECU TH, TH', TH"...Threshold P...Cylinder pressure α・Offset component θ1 First predetermined time θ2・Second predetermined time θ,・Third predetermined time P1' First cylinder pressure P2'/second cylinder pressure P,'...Third cylinder pressure P3'' Calculated values β, β', β'' of third cylinder pressure Explosion stroke pressure information β ′...Integral value β“...Deviation S1...P1
Step S2 of detecting ' and P2'...Step S3 of calculating the offset component α-Step S4 of detecting P and '...Step S4' of calculating explosion stroke pressure information β...Correcting the integral value β' Step S4 “・
・Step S of calculating the deviation β″ between P,′ and P,−
5...Step S5' of calculating the threshold TH
...Step S5" of calculating the threshold TH'
... Step S6 of calculating the threshold TH''...
Step S6' to compare the explosion stroke pressure information with TH; Step 56'' to compare the corrected β' with TH'; Step S8 to compare the deviation β'' with T H''; Step S12 and P to determine the misfire state. Step S1 of calculating the calculated value P3'' of , '
3. Step of calculating integral value β' In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] (1) Detecting first and second in-cylinder pressures at first and second predetermined times during the compression stroke; and detecting an offset component of the pressure sensor based on the first and second in-cylinder pressures. a step of calculating, a step of detecting a third in-cylinder pressure at a third predetermined time during the explosion stroke, a step of obtaining explosion stroke pressure information based on the offset component and the third in-cylinder pressure, calculating a threshold for the explosion stroke pressure information; comparing the explosion stroke pressure information with the threshold; and determining a cylinder misfire condition when the explosion stroke pressure information is less than or equal to the threshold. A misfire detection method for an internal combustion engine. (2) detecting first and second cylinder pressures at first and second predetermined times during the compression stroke; and detecting an offset component of the pressure sensor based on the first and second cylinder pressures. calculating an integral value of the cylinder pressure from the second predetermined time to a third predetermined time during the explosion stroke; correcting the integral value based on the offset component; the step of calculating a threshold for the integral value; the step of comparing the corrected integral value with the threshold; and the step of determining a cylinder misfire state when the corrected integral value is less than or equal to the threshold. A misfire detection method for internal combustion engines. (3) detecting first and second cylinder pressures at first and second predetermined times during the compression stroke; and detecting the third cylinder pressure during the explosion stroke based on the first and second cylinder pressures. a step of calculating a third in-cylinder pressure at a predetermined time period; a step of detecting a third in-cylinder pressure at the third predetermined time period; and a deviation between the calculated value and the detected value of the third in-cylinder pressure. calculating a threshold for the deviation; comparing the deviation with the threshold; and determining a cylinder misfire condition if the deviation is less than or equal to the threshold. Engine misfire detection method.