JP2010014065A - Combustion state determination method and device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine a combustion state in a cylinder having a broken in-cylinder pressure sensor and a cylinder having no in-cylinder pressure sensor even if the in-cylinder pressure sensor is broken or the in-cylinder pressure sensors are not installed to the whole cylinders. <P>SOLUTION: A combustion state determination method for an engine comprises a standard correlation drawing forming means 44 for obtaining in-cylinder maximum pressure data from an in-cylinder pressure detection value detected from the in-cylinder pressure sensor 38 and forming a standard correlation drawing from a correlative value by calculating the correlative value between cylinders wherein one cylinder is at a designated combustion state including a normal combustion state in advance on the basis of the maximum pressure data, an actual correlation drawing forming means 46 for forming an actual correlation drawing from correlative values between remained cylinders on the basis of the in-cylinder maximum pressure data of each of remained cylinders during an actual operation, and a determination means 48 for determining the combustion state of one cylinder in pattern comparison between the standard correlation drawing and the actual correlation drawing. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a determination method and a determination apparatus for a combustion state in a gas engine and a diesel engine. In particular, even if a cylinder pressure sensor fails, it is possible to determine misfire in a cylinder or abnormal decrease in cylinder pressure. It is an invention to do.

  In gas engines and diesel engines, for stable operation, spontaneous combustion of end gas due to premature ignition due to surface ignition such as high-temperature parts in the combustion chamber or deposited unburned carbon, exfoliated carbon, and non-uniform mixture concentration Reliably detect the occurrence of fire and knocking and take prompt action, and reliably detect excessive increases or abnormal drops in the maximum pressure in the combustion chamber, that is, the maximum in-cylinder pressure, and take immediate action Therefore, it is required to maintain engine durability and performance stability.

As a diagnostic apparatus for detecting and diagnosing the combustion state in the combustion chamber of the engine, a technique such as Patent Document 1 (Japanese Patent Laid-Open No. 2007-170405) has been proposed.
In Patent Document 1, as shown in FIG. 18, the differential pressure ΔP (ΔP = P-P _b of the compression start previous reference pressure P _b which includes an intake pressure and in-cylinder pressure detection value P in the combustion chamber of the gas engine ) Corresponding to the crank angle, and using the in-cylinder pressure ratio ΔP / ΔP ₀ between the differential pressure ΔP at each crank angle and the differential pressure ΔP _{0 at} one or more arbitrary points in the compression stroke, A configuration for diagnosing a combustion state such as an in-cylinder pressure state is shown. As the in-cylinder pressure detection value P, the in-cylinder pressure ratio ΔP _max / ΔP ₀ using the in-cylinder maximum pressure P _max and the in-cylinder pressure ratio ΔP ₁ / ΔP ₀ using P ₁ in the combustion stroke Whether or not is appropriate.

Further, as an example of a technique for determining misfire based on a pressure signal from an in-cylinder pressure sensor, there is JP-A-2006-152895. Patent Document 2 discloses a technique for extracting a pressure component generated by combustion from the output of a pressure sensor installed in a cylinder and detecting the combustion state based on this component, and is obtained from the output of the pressure sensor. detecting a misfire by calculating the combustion parameter Cr is a correlation between in-cylinder pressure P _C to be. It is shown that the combustion parameter Cr is calculated as a product of the in-cylinder pressure discrete value P _C (i) obtained at a predetermined rate and a reference signal Fe (i) synchronized therewith.

  Further, in Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-2329), the calculation is based on the indicated torque heat quantity calculated by multiplying the combustion chamber pressure detected by the in-cylinder pressure sensor by the combustion chamber volume and the fuel supply amount. A technique is shown in which the indicated thermal efficiency is obtained from the ratio to the quantity of heat supplied to the fuel, and the misfire of the internal combustion engine is determined by comparing the indicated thermal efficiency with a preset misfire determination value.

JP 2007-170405 A JP 2006-152895 A JP 2008-2329 A

However, in any of the techniques disclosed in Patent Documents 1, 2, and 3, it is necessary to provide each cylinder with at least one in-cylinder pressure sensor in order to determine the combustion state.
Further, the determination method of the combustion state in Patent Documents 1, 2, and 3 is to calculate and determine the pressure ratio, the combustion parameter, the heat amount, and the like based on the pressure in the combustion chamber of the determination target cylinder. For cylinders with in-cylinder pressure sensors damaged, or cylinders with in-cylinder pressure sensors determined to be abnormal, the combustion state cannot be grasped, and a misfire condition can be detected until a new in-cylinder pressure sensor is replaced. Therefore, there is a possibility that appropriate avoidance operation for the cylinder is not performed quickly.

  Furthermore, since it is necessary to provide each cylinder with at least one in-cylinder pressure sensor, a multi-cylinder engine such as V12 or V16 has a large number of in-cylinder pressure sensors, a large number of wires, and maintenance. In addition, there is a problem that the cost is high for an engine not provided with an in-cylinder pressure sensor.

  Therefore, the present invention has been made in view of such a background, and the in-cylinder pressure sensor can be used even if the in-cylinder pressure sensor fails or no in-cylinder pressure sensor is installed for all the cylinders. It is an object of the present invention to provide an engine combustion state determination method and apparatus capable of determining a combustion state even for a cylinder in which an in-cylinder pressure sensor is not installed with respect to a cylinder having a malfunction.

  In order to solve the above-described problem, a first aspect of the present invention provides a combustion state determination method for an engine that determines a combustion state in a cylinder based on a detected in-cylinder pressure value detected by an in-cylinder pressure sensor. In-cylinder maximum pressure data is obtained from the detected internal pressure value, and a cross-correlation value between the cylinders when one cylinder is in a predetermined combustion state including a normal combustion state is calculated in advance from the data. A reference cross-correlation diagram is created by displaying as a correlation diagram, and an actual cross-correlation diagram is created from the cross-correlation values between the cylinders based on the in-cylinder maximum pressure data of the remaining cylinders during actual operation. The combustion state of the one cylinder is determined by pattern matching between an actual cross-correlation diagram and the reference cross-correlation diagram.

  The second aspect of the invention relates to a combustion state determination device for carrying out the combustion state determination method, wherein the combustion state in the cylinder is determined based on the in-cylinder pressure detection value detected by the in-cylinder pressure sensor. In the engine combustion state determination device for determining, in-cylinder maximum pressure data is acquired from the in-cylinder pressure detection value, and one cylinder in advance is in a predetermined combustion state including a normal combustion state based on the data. Based on reference cross-correlation diagram creation means for calculating a cross-correlation value, displaying the calculation result as a cross-correlation diagram and creating a reference cross-correlation diagram, and in-cylinder maximum pressure data of each remaining cylinder during actual operation An actual cross-correlation diagram creating means for creating an actual cross-correlation diagram from the cross-correlation values between the remaining cylinders, an actual cross-correlation diagram by the actual cross-correlation diagram creating means, and a basis by the reference cross-correlation diagram creating means By pattern matching between the cross-correlation diagram and further comprising a judging means for judging the combustion state of said one cylinder.

According to the combustion state determination method and apparatus of the present invention, the in-cylinder pressure obtained from another healthy cylinder with respect to the cylinder in which the in-cylinder pressure sensor has failed and the cylinder without the in-cylinder pressure sensor. Since information is statistically comprehensively evaluated and determined, it is possible to grasp and determine a combustion state that cannot be observed with high detection accuracy.
As a result, it is possible to perform an avoidance measure against abnormal combustion (stopping of fuel supply, etc.) for the failed cylinder while operating the engine until the failed sensor is replaced, and to ensure safe operation of the engine.

That is, since the multi-cylinder engine has a piston connected to one crankshaft, the cylinders operate while interfering with each other.
For this reason, even if the in-cylinder pressure sensor of a specific cylinder has failed or no in-cylinder pressure sensor is installed, the in-cylinder pressure sensor will fail if a combustion abnormality occurs. Or in-cylinder pressure in the cylinder in which the in-cylinder sensor is installed.
Therefore, by processing the pressure information from the in-cylinder pressure sensor of the cylinder in which the in-cylinder pressure sensor is not broken or in which the in-cylinder sensor is installed, using the cross-correlation value which is a statistical processing method, The combustion state can also be determined for a cylinder in which the in-cylinder pressure sensor is broken or in which the in-cylinder pressure sensor is not installed.

  In this determination, first, in-cylinder maximum pressure data is acquired from the in-cylinder pressure sensor, and a cross-correlation value between the cylinders when one cylinder is in a predetermined combustion state including a normal combustion state is calculated in advance from the data. Then, the calculation result is displayed as a cross-correlation diagram to create a reference cross-correlation diagram. Then, in actual operation, the in-cylinder pressure sensor is broken, or an actual cross-correlation diagram is created from the cross-correlation values between the remaining cylinders based on the in-cylinder maximum pressure data of each cylinder other than the cylinder not installed, The combustion state of the one cylinder is determined by pattern matching between the actual cross-correlation diagram and the reference cross-correlation diagram, that is, pattern matching.

The in-cylinder maximum pressure P _max of a cylinder that has not failed due to combustion control is kept substantially constant. However, if there is a misfired cylinder, the ignition order has the greatest effect on the preceding and succeeding cylinders, and the ignition order is It has little effect on the farthest cylinders.
Therefore, it is possible to indirectly identify which cylinder is misfiring by examining the degree of influence between each cylinder with respect to P _max using the cross-correlation value.

As the cross-correlation value, a cross-correlation value of a statistical method is used.
Assuming that the data sequence of the cylinder Kx in the most recent N cycle is X and the data sequence of the cylinder Ky is Y, the cross-correlation values ρ _{x and y} are ρ _{x, y} = Cov (X, Y) / (σ _x × σ _y ), Where σ _x and σ _y are standard deviations of the data string X of the cylinder Kx and the data string Y of the cylinder Ky, and Cov (X, Y) = Σ (X _j −μ _x ) × (Y _j −μ _y ) is the covariance of X and Y.

The cross-correlation diagram is created as follows.
The cross-correlation values ρ _{x and y} calculated by the equation (1) are plotted at the intersections corresponding to the cylinder numbers on the coordinates with the cylinder numbers on the vertical axis and the horizontal axis in the firing order, and A cross-correlation diagram is created by a diagram drawn by connecting correlation values.
10 and 11 show examples of reference cross-correlation diagrams that are created in this way and serve as normal references. Then, the reference cross-correlation diagram pattern and the actual cross-correlation diagram pattern obtained during actual operation are collated, that is, by pattern matching, the in-cylinder pressure sensor 38 fails or the combustion state of the cylinder not installed Determine.

  In this method invention, preferably, the combustion state is a misfire or a decrease in compression pressure, and the pattern of the actual cross-correlation diagram matches the pattern of the reference cross-correlation diagram at the time of misfire or a decrease in compression pressure of a specific cylinder. In this case, it may be determined that the specific cylinder is misfired or the compression pressure is reduced, and when the actual cross-correlation diagram pattern matches the reference cross-correlation diagram pattern at normal time, the normal cylinder state may be determined. .

  In the apparatus invention, it is preferable that the combustion state is a misfire or a decrease in compression pressure, and the combustion state determination means uses the reference when the pattern of the actual cross-correlation diagram is a misfire or a decrease in compression pressure of a specific cylinder. When the pattern of the cross-correlation diagram matches, the specific cylinder may be determined to be in a misfire or a reduced compression pressure state, and the combustion state determination means may determine the reference cross-correlation diagram when the actual cross-correlation diagram pattern is normal. If the pattern matches, it is good to determine that the state is normal.

  As a result, it is possible to obtain from other healthy cylinders that the combustion state is misfiring or that the compression pressure is reduced even for a cylinder in which the in-cylinder pressure sensor has failed, and even for a cylinder in which the in-cylinder pressure sensor is not installed. Can be determined reliably and quickly based on the in-cylinder pressure information.

  In addition, not only abnormal combustion such as misfire or reduced compression pressure, but also the fact that the combustion state is in a normal state can be confirmed by the above pattern matching, so that the reliability of the in-cylinder pressure sensor itself for failure determination can be improved. it can. That is, even if it is determined that the in-cylinder pressure sensor itself is out of order, if it is determined that the normal state is obtained from the comparison based on the pattern, the determination of misfire and engine control are continued with the signal from the sensor being valid. Can do.

  In the apparatus invention, preferably, the in-cylinder pressure sensor is installed every other ignition order, and the engine is a V-type multi-cylinder engine, and the in-cylinder pressure sensor is provided only in one bank. It should be installed.

  As a result, only half the in-cylinder pressure sensor is used, the cost is reduced, and a space such as wiring is not required, so that the space around the engine can be effectively used and the apparatus can be made compact. Furthermore, since the number of parts used is reduced, the reliability of the entire engine is improved.

  According to the present invention, even if the in-cylinder pressure sensor fails or no in-cylinder pressure sensor is installed for all the cylinders, the in-cylinder pressure sensor is further applied to the cylinder in which the in-cylinder pressure sensor has failed. It is possible to provide an engine combustion state determination method and apparatus capable of determining a combustion state even for cylinders that are not installed.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Only.

(First embodiment)
FIG. 1 is a configuration diagram showing the overall configuration of a combustion state determination device 4 for an engine 2 according to the first embodiment of the present invention.
In FIG. 1, an engine 2 is an example of a gas engine, and is a multi-cylinder, 12-18 cylinder V type four-cycle gas engine. The engine is not limited to a gas engine.
A piston 8 is fitted in the cylinder 6 so as to be slidable in a reciprocating manner, and a crankshaft 12 for converting the reciprocating motion of the piston 8 into rotation through a connecting rod 10 is provided.
The engine 2 includes a combustion chamber 14 defined between the upper surface of the piston 8 and the inner surface of the cylinder 6, an air supply port 16 and an air supply pipe 18 connected to the combustion chamber 14, and the air supply port 16. And an exhaust port 22 connected to the combustion chamber 14 and an exhaust valve 24 that opens and closes the exhaust port 22.

A gas mixer 26 is installed in the middle of the air supply pipe 18. The fuel gas supplied from the fuel gas pipe 28 through the gas amount adjusting valve 30 and the compressed air supplied from a supercharger (not shown) (not provided with a supercharger). In this case, non-supercharged air) is mixed by the gas mixer 26, and this premixed gas is supplied to the combustion chamber 14 through the supply port 16 and the supply valve 20.
The ignition device 32 includes a pilot injection device that injects a pilot fuel 34 such as light oil into an auxiliary chamber (not shown) by an injection nozzle 36 to ignite and burn it, and jets this combustion flame into the combustion chamber 14.

An in-cylinder pressure sensor 38 is installed in the combustion chamber 14 of each cylinder K (1-12) as shown in FIG. FIG. 2 is a plan view of the engine showing the case of the V12 cylinder.
The combustion state determination device 4 receives the in-cylinder pressure detection values detected by the in-cylinder pressure sensors 38 and the detection value of the crank angle of the engine 2 detected by the crank angle sensor 40.

  The combustion state determination device 4 acquires in-cylinder maximum pressure data Pmax from the in-cylinder pressure detection value, and based on the data, a cross-correlation between cylinders when one cylinder is in a predetermined combustion state including a normal combustion state in advance. A cross-correlation value calculating unit for calculating a value; and a reference cross-correlation diagram creating unit for displaying a calculation result as a cross-correlation diagram to create a reference cross-correlation diagram.

  Further, the cross-correlation value between the remaining cylinders is calculated by the same method as the cross-correlation value calculating means 42 based on the in-cylinder maximum pressure data of the other remaining cylinders during actual operation, and the calculated result is used. The actual cross-correlation diagram creating means 46 for creating the actual cross-correlation diagram, and the pattern of the actual cross-correlation diagram by the actual cross-correlation diagram creating means 46 and the reference cross-correlation diagram by the reference cross-correlation diagram creating means 44 are collated. A judging means 48 for judging the combustion state of one cylinder is provided.

Here, the principle of the combustion state determination method of the present invention will be described.
In the multi-cylinder engine, since the piston 8 is connected to one crankshaft 12, the cylinders operate while interfering with each other.
For this reason, even when the in-cylinder pressure sensor 38 of a specific cylinder has failed or when the in-cylinder pressure sensor 38 is not installed, if a combustion abnormality occurs in the cylinder, the other cylinder The internal pressure sensor 38 is not malfunctioning or affects the in-cylinder pressure in the cylinder K in which the in-cylinder sensor 38 is installed. Therefore, the pressure information from the in-cylinder pressure sensor 38 of the cylinder K in which the in-cylinder pressure sensor 38 is not broken or in which the in-cylinder sensor 38 is installed is processed using the cross-correlation value which is a statistical processing method. Thus, even when the in-cylinder pressure sensor 38 is out of order or when the in-cylinder pressure sensor 38 is not installed, the combustion state in the cylinders K can be determined.

That is, the in-cylinder maximum pressure P _max of a cylinder that has not failed due to the combustion control is kept substantially constant, but if there is a misfired cylinder, the ignition sequence has the greatest effect on the cylinders before and after that, and the ignition It has little effect on the most distant cylinders.
Therefore, it is possible to indirectly identify which cylinder is misfiring by quantitatively expressing the degree of influence between each cylinder with respect to _Pmax by using a cross-correlation value.

FIG. 3 shows the temporal transition of the in-cylinder pressure waveform of a specific cylinder (cylinder 1) and the temporal transition of the in-cylinder pressure waveform for the cylinder to be ignited next (cylinder 2). P1 _max is kept constant by combustion control to keep the in-cylinder maximum pressure constant, and the same waveform is shown every cycle. However, the maximum in-cylinder pressure is slightly increased and decreased due to slight engine rotation unevenness and the like. It appears. Further, it is shown that a similar waveform can be obtained for the next ignition cylinder 2.

FIG. 4 shows the in-cylinder pressure waveform when all the cylinders of the engine are operating in a normal combustion state, with the crank angle as the horizontal axis, and the cylinder 1 or cylinder of an n-cylinder multi-cylinder engine is shown. The state during one cycle up to n is shown in the firing order.
When the engine is operating at a constant speed and a constant load as shown in FIGS. 3 and 4, the in-cylinder pressure waveforms of all the cylinders have substantially the same shape without a range of combustion variations.
FIG. 5 is a diagram showing a tendency with respect to fluctuations in the in-cylinder pressure waveform in which the ignition order is adjacent in the normal combustion state. The degree of influence is large only in the adjacent in-cylinder pressure waveform, and the tendency of increase and decrease in P _max is similar. However, the degree of influence decreases as the ignition order goes away, and the influence is reduced most in the farthest cylinder h.

Next, FIGS. 6, 7, and 8 are diagrams corresponding to FIGS. 3, 4, and 5, for example, in-cylinder pressure waveforms of all cylinders when the cylinder 2 misfires.
The in-cylinder maximum pressure of each cylinder that has not misfired is kept substantially constant by combustion control that keeps the maximum pressure constant. However, in the cylinder 2 that has misfired, the maximum cylinder pressure decreases. Furthermore, the maximum in-cylinder pressure for each cycle slightly changes due to the influence of slight engine rotation unevenness and the like. When the in-cylinder pressure of the cylinder that is misfiring is reduced with respect to the slight change caused by the uneven rotation, the cylinders whose ignition order is adjacent are most affected, and P _max is lower than usual and misfires. It is shown that when the in-cylinder pressure of the cylinder rises, the cylinder whose ignition order is adjacent is most affected, and P _max rises more than usual, and the influence appears more noticeably than other cylinders. That is, the pressure fluctuation tendency of the cylinder whose ignition order is adjacent to the cylinder 2 becomes the same tendency as the pressure fluctuation of the misfired cylinder 2, and the pressure fluctuation of the cylinder 2 in the cylinder h where the ignition order is farthest. Are unrelated and have the least impact.

Therefore, in order to realize a quantitative relative comparison with other cylinders, the cross-correlation value of the statistical method is used.
Assuming that the data string of the cylinder Kx of the most recent N cycles is X and the data string of the cylinder Ky is Y, the cross-correlation values ρ _{x, y} are expressed by the equation (1).
ρ _{x, y} = Cov (X, Y) / (σ _x × σ _y ) (1)
Here, σ _x , σ _y = standard deviation of the data string X of the cylinder Kx and the data string Y of the cylinder Ky.
Cov (X, Y) = Σ (X _j −μ _x ) × (Y _j −μ _y )... Covariance of X and Y.

A cross-correlation value ρ _{x, y} is calculated for the mutual combination of all the cylinders Kx and Ky during normal combustion. For example, in the case of the V16 cylinder, there are 256 combinations of all cylinders.
For example, the cross-correlation value table shown in FIG. Then, the respective cross-correlation values ρ _{x, y} are plotted at the intersections corresponding to the cylinder numbers on the coordinates where the cylinder numbers are taken in the firing order on the vertical and horizontal axes, and the equal cross-correlation values of the plotted cross-correlation values are A cross-correlation diagram is created by a diagram drawn by connection.

Examples of cross-correlation diagrams created in this way are shown in FIGS.
FIG. 10 shows the results of a cross-correlation diagram when all cylinders are normally burning. The vertical axis and the horizontal axis indicate cylinder numbers in order of ignition, and there is a strong correlation only with the cylinders whose ignition order is adjacent during normal combustion. The cross-correlation value of the combination part of the same cylinder is the strongest and becomes 1, and the strongest cross-correlation value is shown linearly.

FIG. 11 shows a cross-correlation diagram of all cylinders when the cylinder 4 misfires, for example. A characteristic pattern is that the region where the cross-correlation value is weak spreads in four directions from the intersection of the cylinders 11 and 11. This is a manifestation of a weak influence state in a cylinder in the vicinity where the firing order is farthest from the cylinder 4.
12 assumes that the cylinder pressure sensor 38 of the cylinder 4 becomes unusable due to a failure, that is, the cylinder 4 misfires on the assumption that the information of the cylinder pressure sensor 38 of the cylinder 4 cannot be used. The cross-correlation diagram in a state is shown.
Even if the cylinder 4 is in an unusable state, if the cylinder 4 is misfired, the intersection of the cylinder 11 and the cylinder 11 which is a characteristic pattern in the case where the cylinder 4 is misfired also in FIG. A pattern in which a cross-correlation region having a weak cross-correlation is spreading in all directions appears.

Accordingly, when it is determined that the in-cylinder pressure sensor 38 is out of order, the pressure information of the cylinder 4 cannot be obtained. Therefore, only the cross-correlation diagram as shown in FIG. 12 can be obtained. A distinctive pattern of misfire can be identified.
When misfire occurs, the balance is lost, and the influence of the interaction between the cylinders becomes stronger (the cross-correlation value of the misfire state of the cylinder 4 in FIGS. 11 and 12 is stronger than the whole in FIG. 10, and the whole becomes black. It is possible to clearly grasp the characteristic tendency that the cylinder whose ignition order is farthest from the misfired cylinder 4 is weaker than the other cylinders.

It should be noted that the failure determination of the in-cylinder pressure sensor 38 is within the allowable range of the standard deviation during a predetermined cycle of the differential pressure ΔP ₀ = (P ₀ −P _b ) at the pressure P ₀ (see FIG. 2) at the specific crank angle before combustion. Judgment is made based on whether or not it is within.

As described above, a cross-correlation diagram when each cylinder misfires is set as a reference cross-correlation diagram in advance, and is acquired in advance when the in-cylinder pressure sensor is determined to be abnormal during actual operation. Whether or not misfire has occurred can be determined by pattern matching with the pattern of the reference cross-correlation diagram.
As a pattern matching method, a special method is not used, but pattern matching can be performed by Mahalanobis Taguchi method.

Next, control in the combustion state determination device 4 will be described with reference to a control flowchart shown in FIG. The determination of the misfire state will be described.
First, when control is started in step S1, the cylinder K to be determined is set to cylinder 1 in step S2. In step 3, it is determined whether the cylinder 1 is determined to be abnormal in the cylinder pressure sensor 38. This sensor abnormality is determined from the fluctuation range of the standard deviation of ΔP ₀ as described above. If the sensor is not abnormal, a misfire determination is performed using the in-cylinder pressure sensor 38 of the cylinder 1 in step S4, and it is determined whether or not the misfire determination result is a misfire state in step S5. In step S6, the process proceeds as it is without performing the combustion control, and when it is not in the misfire state, the combustion control is performed in step S7. Then, in step S8, the cylinder of the next cylinder number is set as a determination target, and in step S9, it is determined whether the cylinder number K has reached the number of N cylinders of the engine, that is, whether all the cylinders have been checked. If so, the determination ends in step S10.

Further, if it is determined in step S3 that the in-cylinder pressure sensor of cylinder 1 is abnormal, the process proceeds to step 11 and the cross-correlation is performed from the in-cylinder pressure signals for the past m cycles of the N-1 cylinder excluding cylinder 1. Calculate the value and create an actual cross-correlation diagram.
Next, in step 12, the reference cross-correlation diagram when the cylinder 1 for which the actual cross-correlation diagram has been prepared in advance is in a misfire state is collated with the pattern.

  In step S13, if the characteristic pattern of the cross-correlation diagram, that is, the occurrence pattern of the weak cross-correlation region as described above appears in the same manner as a result of the collation, the cylinder 1 is in a misfire state. The process proceeds to step S6 and combustion control is not performed. If the characteristic part of the cross-correlation diagram is different in step S13, it is determined that there is no misfire state, and the process proceeds to step S7 where combustion control is performed. Thereafter, in step S8, the cylinder of the next cylinder number is set as a determination target. In step S9, it is determined whether the cylinder number K has reached the number of N cylinders of the engine. If it has been reached, the determination is ended in step S10.

  13 is configured to be executed by the reference cross-correlation diagram creating unit 44, the actual cross-correlation diagram creating unit 46, and the determining unit 48 in the combustion state determination device 4. .

According to the first embodiment described above, for the cylinder in which the in-cylinder pressure sensor 38 has failed, the cross-correlation value is calculated from the in-cylinder pressure information obtained from another healthy cylinder, and the cross-correlation diagram is obtained from the calculation result. Is created by evaluating the cross-correlation diagram based on a reference cross-correlation diagram as a reference and pattern matching, so that it is possible to grasp and determine the combustion state that cannot be directly observed with high detection accuracy.
As a result, even before the failed in-cylinder pressure sensor is replaced, the engine can be operated while avoiding abnormal combustion (stopping fuel supply, etc.) for the failed cylinder, and the engine can be operated safely. It can be secured.

(Second Embodiment)
Next, a second embodiment will be described.
In the first embodiment, the method for determining the misfire state without using the abnormal in-cylinder pressure sensor 38 when the in-cylinder pressure sensor 38 is determined to be abnormal has been described. In the second embodiment, Without installing in-cylinder pressure sensors in all cylinders of the multi-cylinder engine, every other cylinder is installed in order, and combustion is performed for the cylinders that are not installed using the method described in the first embodiment. The state is determined.

  FIG. 14 shows a plan view of a V12 cylinder engine corresponding to FIG. 2, and the combustion state determination device 4 has only one bank on the right side, for example, odd-numbered cylinders (1, 3, 5,...). An in-cylinder pressure sensor 38 is installed, and the in-cylinder pressure detection value detected by each in-cylinder pressure sensor 38 and the detected value of the crank angle of the engine 2 detected by the crank angle sensor 40 are input.

  In the combustion state determination device 4, the reference cross-correlation diagram creating means 44 creates in advance a reference cross-correlation diagram during normal operation when the cylinder pressure sensor 38 is installed only in one bank of the V16 engine. An example of the reference cross-correlation diagram during normal operation is shown in FIG. Further, in this state, for example, a reference cross-correlation diagram when the cylinder 4 is in a misfire state is shown in FIG.

  As can be seen from the reference cross-correlation diagram of FIG. 16, it is possible to recognize the same pattern as in the case where in-cylinder pressure sensors are installed in all the cylinders of the first embodiment and the cylinders 4 are misfired. That is, when the cylinder 4 is misfired, there is a pattern in which a region where the cross-correlation value is weak in a cross shape spreads in four directions from the intersection of the cylinder 11 and the cylinder 11 which are in the vicinity of the ignition cylinder farthest from the cylinder 4. Appears.

  Accordingly, as shown in FIGS. 15 and 16, the pattern of the reference cross-correlation diagram can be clearly distinguished with a significant difference between the normal combustion and the misfire state. Since it can be determined as a characteristic pattern similar to the case where the in-cylinder pressure sensor is installed in the cylinder, the misfire state of the specific cylinder can be determined even when the in-cylinder pressure sensor is installed only in one bank.

  As a result, the cylinder pressure sensor 38 to be used can be cut in half, and the cost can be reduced, and a space such as wiring can be eliminated, and the space around the engine can be effectively used and the apparatus can be made compact. Furthermore, since the number of parts used is reduced, the reliability of the entire engine is improved.

(Third embodiment)
Next, a third embodiment will be described.
In the first embodiment and the second embodiment, the determination method when the compression pressure is reduced as in the misfire combustion state has been described. In the third embodiment, it is determined that the inside of the cylinder is in the normal combustion state and the cylinder is This improves the reliability of the abnormality determination of the internal pressure sensor.

Based on the normal reference cross-correlation diagram patterns shown in FIGS. 10 and 15, as shown in FIG. 17, the reference cross-correlation diagram is collated in step S <b> 12 of the flowchart of FIG. 13. If the state pattern is determined, the process may return to step S4 to determine the misfire state based on the output value of the in-cylinder pressure sensor 38.
As described above, the determination of the abnormality of the in-cylinder pressure sensor 38 can be improved by determining even when the combustion state is normal by comparing the reference cross-correlation diagram and the actual cross-correlation diagram.
Subsequently, the misfire determination and the engine control can be continued by making the signal from the in-cylinder pressure sensor 38 effective.

  According to the present invention, even if the in-cylinder pressure sensor fails or no in-cylinder pressure sensor is installed for all the cylinders, the in-cylinder pressure sensor is further applied to the cylinder in which the in-cylinder pressure sensor has failed. Since it is possible to determine the combustion state even for cylinders that are not installed, it is useful when applied to a combustion state determination method and determination device for an internal combustion engine such as a gas engine or a diesel engine.

1 is an overall configuration diagram of an engine combustion state determination apparatus according to a first embodiment of the present invention. It is explanatory drawing which shows the planar view of a multi-cylinder engine of V12 cylinder. It is explanatory drawing which shows the time transition of the cylinder pressure waveform of the cylinder 1 and the cylinder 2. FIG. It is explanatory drawing which shows the cylinder pressure waveform when all the cylinders of an engine are operate | moving in a normal combustion state. It is explanatory drawing which shows the tendency with respect to the fluctuation | variation of the cylinder pressure waveform to which the ignition order adjoined in the case of a normal combustion state. FIG. 4 is a diagram corresponding to FIG. 3 when a cylinder 2 misfires. FIG. 5 is a diagram corresponding to FIG. 4 when a cylinder 2 misfires. FIG. 6 is a diagram corresponding to FIG. 5 when a cylinder 2 misfires. It is explanatory drawing which shows the illustration of a cross correlation value table | surface. It is a cross-correlation diagram between the cylinders when all the cylinders are normally burning. It is a cross-correlation diagram of all the cylinders when the cylinder 4 is misfired. FIG. 6 is a cross-correlation diagram when the cylinder 4 is misfired and the cylinder pressure sensor of the cylinder 4 cannot be used. It is a flowchart of the determination control in a combustion state determination apparatus. FIG. 3 is a diagram corresponding to FIG. 2 of a second embodiment of the present invention. It is a cross-correlation diagram of the normal combustion state in the second embodiment. It is a cross-correlation diagram when the cylinder 4 in the second embodiment misfires. FIG. 14 is a diagram corresponding to FIG. 13 of a third embodiment of the present invention. It is explanatory drawing which shows the relationship between the in-cylinder pressure observed and the combustion state.

Explanation of symbols

2 Engine 4 Combustion state determination device 6 Cylinder 12 Crankshaft 38 In-cylinder pressure sensor 40 Crank angle sensor 42 Cross-correlation value calculation means 44 Reference cross-correlation diagram creation means 46 Real cross-correlation diagram creation means 48 Determination means

Claims (10)

In the engine combustion state determination method for determining the combustion state in the cylinder based on the in-cylinder pressure detection value detected by the in-cylinder pressure sensor,
In-cylinder maximum pressure data is acquired from the in-cylinder pressure detection value, and a cross-correlation value between cylinders when one cylinder is in a predetermined combustion state including a normal combustion state is calculated in advance from the data, and the calculation result Is created as a cross-correlation diagram and a reference cross-correlation diagram is created, and an actual cross-correlation diagram is created from the cross-correlation values between the cylinders based on the in-cylinder maximum pressure data of the remaining cylinders during actual operation. An engine combustion state determination method comprising: determining a combustion state of the one cylinder by pattern matching between the actual cross-correlation diagram and the reference cross-correlation diagram.   The cross-correlation value is calculated using a cross-correlation value calculation formula used for statistical processing, and the cross-correlation value of the calculation result is plotted at the intersection of the cylinder numbers on the coordinates with the cylinder numbers on the vertical and horizontal axes, respectively. 2. The engine combustion state determination method according to claim 1, wherein the cross-correlation diagram is created by a diagram drawn by connecting equal cross-correlation values of the plotted cross-correlation values.   When the combustion state is misfire or the compression pressure is reduced, and the pattern of the actual cross-correlation diagram matches the pattern of the reference cross-correlation diagram at the time of misfire or compression pressure drop of the specific cylinder, the specific cylinder is misfired 3. The engine combustion state determination method according to claim 1 or 2, wherein the determination is a compression pressure drop state.   The engine combustion state determination method according to claim 1 or 2, wherein when the actual cross-correlation diagram pattern matches the normal cross-correlation pattern pattern, the normal state is determined. In a combustion state determination device for an engine that determines a combustion state in a cylinder based on an in-cylinder pressure detection value detected by an in-cylinder pressure sensor,
In-cylinder maximum pressure data is acquired from the in-cylinder pressure detection value, and a cross-correlation value between cylinders when one cylinder is in a predetermined combustion state including a normal combustion state is calculated in advance from the data, and the calculation result A reference cross-correlation diagram creating means for creating a reference cross-correlation diagram by displaying as a cross-correlation diagram;
Real cross-correlation diagram creating means for creating a real cross-correlation diagram from cross-correlation values between the remaining cylinders based on the in-cylinder maximum pressure data of the remaining cylinders during actual operation;
And determining means for determining the combustion state of the one cylinder by pattern matching between the actual cross-correlation diagram by the actual cross-correlation diagram creating means and the reference cross-correlation diagram by the reference cross-correlation diagram creating means. An engine combustion state determination device.   The reference cross-correlation diagram creating means and the actual cross-correlation diagram creating means obtain the cross-correlation value by the calculation formula of the cross-correlation value used for the statistical processing, respectively, and the cylinder numbers on the coordinates with the cylinder numbers on the vertical axis and the horizontal axis 6. The engine combustion state determination device according to claim 5, wherein the cross-correlation value is plotted at an intersection of the cross-correlation values, and a cross-correlation diagram is created by a diagram drawn by connecting equal cross-correlation values of the cross-correlation values. .   The combustion state is a misfire or a decrease in compression pressure, and the combustion state determination means determines that the actual cross-correlation diagram pattern matches the pattern of the reference cross-correlation diagram at the time of misfire or a decrease in compression pressure of a specific cylinder. 6. The engine combustion state determination device according to claim 5, wherein the specific cylinder is determined to be in a misfire or a compression pressure drop state.   6. The engine combustion state determination according to claim 5, wherein the combustion state determination unit determines that the state is normal when the pattern of the actual cross-correlation diagram matches the pattern of the reference cross-correlation diagram at normal time. apparatus.   6. The engine combustion state determination device according to claim 5, wherein the in-cylinder pressure sensor is installed every other ignition order.   6. The engine combustion state determination device according to claim 5, wherein the engine is a V-type multi-cylinder engine, and the in-cylinder pressure sensor is installed only in one bank.

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