JP2009203883A - Failure cause estimating method and device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure cause estimating method and device for an internal combustion engine providing quick correspondence action by accurately specifying a failure cause from occurred states of abnormal combustion such as misfire, extinction, and knocking determined on the basis of a cylinder pressure detected value in a combustion chamber. <P>SOLUTION: In the failure cause estimating method for the internal combustion engine including a gas engine composed so as to mix air with fuel gas and carry out combustion in the combustion chamber of the engine, the cylinder pressure and a crank angle of the engine in the combustion chamber are detected, a first failure state is determined on the basis of the cylinder pressure at a constant crank angle in a compression stroke and a combustion stroke, a second failure state is determined by different determination references being a pressure in a crank angle different from the cylinder pressure or a cylinder pressure in the same crank angle, and an occurrence portion of the failure cause is estimated on the basis of whether or not the second failure state has occurred after the first failure state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a failure cause estimation method and an estimation device for an internal combustion engine including a gas engine and a diesel engine, and in particular, is an invention for estimating the cause of failure such as misfire, extinguishing, knocking, and the like.

In an internal combustion engine, particularly a gas engine whose main fuel is clean gas such as city gas, when the main fuel gas is not sufficiently supplied into the combustion chamber, or the pilot fuel is sufficiently supplied to the sub-chamber ignition device. If the air supply amount fluctuates due to failure of the air supply supercharger, misfiring, extinguishing, knocking, etc. may occur due to insufficient ignition fuel or fluctuations in the gas fuel mixture concentration .
Accordingly, it is required to reliably identify the occurrence of such a failure and take prompt action to maintain the durability and performance stability of the engine.

  For example, the cause of misfire occurrence is estimated by measuring the misfire occurrence rate and using this occurrence rate occurrence pattern. That is, a load map is created from the engine speed and the load, and a pattern is identified as to which region on the load map has a high misfire rate. For example, when the misfire rate is high in a high rotation and high load region, it is estimated that the cause is an insufficient fuel discharge amount.

On the other hand, as techniques for detecting a combustion state such as misfire, extinguishing, knocking, etc. in a combustion chamber of an internal combustion engine, Japanese Patent Application Laid-Open No. 2005-9457 (Patent Document 1) and Japanese Patent Application Laid-Open No. 9-178617 (Patent Document 2). Etc. are known.
In Patent Document 1, a compression pressure ratio between a reference in-cylinder pressure during a compression stroke and a compression pressure at a top dead center is calculated based on the in-cylinder pressure detection value and the crank angle detection value in the combustion chamber. A technique is described in which a combustion state is diagnosed using a compression pressure ratio to determine abnormal combustion such as pre-ignition, misfire, knocking, and the like.

  Further, in Patent Document 2, misfire is detected from the rotation fluctuation of the crankshaft, the misfire rate of the misfire number with respect to the number of ignitions in a predetermined operation region according to the engine rotation speed and the engine load is calculated, and the cause of misfire is calculated. Is shown for each predetermined operating region based on the misfire rate.

JP 2005-9457 A JP-A-9-178617

However, Patent Document 1 discloses a method for diagnosing the combustion state based on the in-cylinder pressure detection value in the combustion chamber and determining abnormal combustion such as pre-ignition, misfire, knocking, etc. A method for estimating the cause of the occurrence is not shown, and it is not sufficient for identifying the cause.
Further, Patent Document 2 discloses a method for estimating the cause of misfire based on the misfire rate for each predetermined operating region. However, the failure is uniquely determined from the engine operating state determined from the engine speed and the engine load. The cause of the problem may not be identified. For example, a misfire may occur due to an abnormality in the ignition coil even in a high-speed and high-load operation region, so that it may not be sufficient to identify the cause of the failure, and an erroneous determination may occur.

  Therefore, the present invention has been made in view of such a background, and it is possible to accurately determine the cause of failure from the occurrence of abnormal combustion such as misfire, extinguishing, knocking, etc., determined based on the in-cylinder pressure detection value in the combustion chamber. It is an object of the present invention to provide a failure cause estimation method and apparatus for an internal combustion engine that can be promptly dealt with by specifying well.

  In order to solve the above problems, the present invention relates to a failure cause estimation method for an internal combustion engine including a gas engine configured to mix fuel gas with air and burn the fuel gas in the combustion chamber of the engine. The internal pressure and the crank angle of the engine are detected, the first failure state is determined based on the in-cylinder pressure at a constant crank angle in the compression stroke and the combustion stroke, and the pressure at a crank angle different from the in-cylinder pressure or the same A second failure state is determined based on different determination criteria that are in-cylinder pressure at a crank angle, and a failure cause occurrence portion is estimated based on a combination of the occurrence of the first failure state and the occurrence of the second failure state. It is characterized by.

  An apparatus for carrying out such a method invention includes a failure cause estimating apparatus for an internal combustion engine including a gas engine configured to mix fuel gas with air and burn the fuel gas in the combustion chamber of the engine. An in-cylinder pressure detector for detecting the in-cylinder pressure and a crank angle detector for detecting the crank angle of the engine are provided, and during the compression stroke and the combustion stroke from the in-cylinder pressure detector and the crank angle detector. The first failure determination means for determining the first failure state based on the detected value of the in-cylinder pressure at a constant crank angle, and the second failure state by a pressure different from the in-cylinder pressure or the same and different determination criteria A second failure determination means for determining a failure cause and a failure cause occurrence portion is estimated based on a combination of the occurrence of the first failure state and the occurrence of the second failure state Characterized in that a disabled part estimation means.

According to this method and apparatus invention, the first failure is based on the in-cylinder pressure at a constant crank angle during the compression stroke and during the combustion stroke based on the in-cylinder pressure detection value in the combustion chamber and the engine crank angle detection value. Determine the state. Specifically, the presence or absence of occurrence of flame extinction or occurrence of knocking is determined. Further, the second failure state is subsequently determined based on a pressure different from the in-cylinder pressure or the same and different criteria. Specifically, it is determined whether flame extinction has occurred and a misfire has occurred, whether knocking has occurred, and there has been a drop in in-cylinder pressure in the compression stroke near the top dead center.
Whether or not the first failure state has occurred and whether or not the second failure state has occurred, more specifically, whether the flame has extinguished and misfired, or knocking has occurred and the in-cylinder pressure in the compression stroke has decreased The failure part is estimated by the above.

  In this way, because the failure location of the engine is estimated on the basis of different failure conditions that occur subsequently, the failure phenomenon that appears in the engine is less than the estimation of the failure occurrence location according to the operating region based on the engine speed and engine load. Since it is directly detected and determined, the specific accuracy of the cause of the failure is improved.

  Preferably, in the method invention, when the first failure state and the second failure state occur in a plurality of cylinders at a certain rate or more, it may be estimated that a failure occurs in a common part of the plurality of cylinders, and the device Also in the present invention, the failure part estimation means may estimate that a failure occurs at a common part of a plurality of cylinders when the first failure state and the second failure state occur in a plurality of cylinders at a certain rate or more.

  According to this method and apparatus invention, when the first failure state and the second failure state occur at a certain rate or more in a plurality of cylinders, it is estimated that a failure occurs at a common part of the plurality of cylinders. When the pilot fuel is supplied to the sub chamber ignition device of the engine by a common rail, if the pilot fuel supply abnormality occurs in a plurality of cylinders, it can be identified as a failure of the common rail. In addition, when an abnormality occurs in the air supply system, the cause site can be identified with a high probability such as a failure of the air supply reservoir of common parts or a supercharger.

  Further, specifically, in the method invention, the internal combustion engine is a gas engine in which fuel gas is mixed with air and supplied to the combustion chamber of the engine, and pilot fuel is supplied to the sub-chamber ignition device for ignition. The first failure state is the occurrence of flame extinction, the second failure state is the occurrence of misfire, and in the case of the occurrence of extinction and the occurrence of misfire, it is assumed that the fuel gas supply system part to the combustion chamber has failed, and the extinction occurs. When there is no misfire and there is no occurrence of misfire, it is estimated that the pilot fuel supply system part has failed.

  In the apparatus for carrying out the method, the internal combustion engine is a gas engine that mixes fuel gas with air and supplies the fuel gas to the combustion chamber of the engine, and supplies pilot fuel to the sub-chamber ignition device for ignition. The first failure state is the occurrence of flame extinction, the second failure state is the occurrence of misfire, and the failure site estimation means is configured to detect a failure of a fuel gas supply system to the combustion chamber in the case of the occurrence of flame extinction and the occurrence of misfire. It is estimated that when there is a flame extinction and there is no misfire, it is estimated that the pilot fuel supply system has failed.

  According to such a method and apparatus invention, when the occurrence of extinction in the first failure state and the occurrence of misfire in the second failure state, it is assumed that the gas supply system portion of the main fuel to the combustion chamber has failed, and the extinction If there is an occurrence and no misfire occurs, it is estimated that the pilot fuel supply system has failed.

That is, if the main fuel gas is supplied from the air supply passage, ignition is not normally performed, but the main fuel gas may self-ignite and may become after-burning (extinguishing). Since it is determined that misfire does not occur, when the fire extinguishing state is determined without causing misfire, pilot fuel is not sufficiently supplied to the sub-chamber ignition device instead of the main fuel gas supply system. It can be judged. For this reason, it is estimated that the pilot fuel supply system has failed. Conversely, if misfire has occurred, it is assumed that the main fuel gas supply system has failed.
Furthermore, the failure location can be more reliably identified by adding the method of occurrence ratio of common parts of the plurality of cylinders to the determination method.

  More specifically, in the method invention, the internal combustion engine is a gas engine configured to mix fuel gas with supercharged air from a supercharger and supply the fuel gas to a combustion chamber of the engine, and the first failure If the state is knocking occurrence, the second failure state is a drop in compression pressure near the top dead center of the crank angle, and if there is a knocking occurrence and a drop in compression pressure near the top dead center, It is estimated that, when knocking occurs and the compression pressure does not drop in the vicinity of the top dead center, it is estimated that the fuel gas supply system has failed.

  In an apparatus for performing the method, the internal combustion engine is a gas engine configured to mix fuel gas with supercharged air from a supercharger and supply the fuel gas to a combustion chamber of the engine, and the first failure state is When knocking occurs and the second failure state is a drop in compression pressure near the top dead center of the crank angle, the failure site estimation means supplies power when there is a occurrence of knocking and a drop in compression pressure near the top dead center. It is presumed that the gas system has failed, and when there is knocking and the compression pressure does not drop near the top dead center, it is estimated that the fuel gas supply system has failed.

According to this method and apparatus invention, if there is a knocking occurrence in the first failure state and a compression pressure drop near the crank angle top dead center in the second failure state, it is estimated that the supply system has failed. If knocking occurs and the compression pressure does not drop near the top dead center, it is assumed that the fuel gas supply system has failed.
In other words, the occurrence of knocking occurs in a gas engine because the amount of air is reduced compared to the amount of gas in the main fuel and the gas fuel is in an excess state. Whether it is due to a system failure or not is determined by whether or not a drop in in-cylinder pressure occurs near the top dead center of the crank angle in the compression stroke.

Therefore, if knocking occurs and the compression pressure drops near the top dead center of the crank angle, a sufficient amount of air is not secured for the fuel gas due to a failure of the air supply system, and the gas amount is reduced to air. It can be estimated that the number of
In addition, in the determination of the failure of the air supply system, by adding the method of the occurrence rate in the common parts of the plurality of cylinders, if the failure occurs in common in the plurality of cylinders, the failure of the turbocharger of the common parts, For example, since it can be presumed to be due to supercharged air surging, the failure part can be identified more reliably.
If knocking occurs but the compression pressure does not drop near the top dead center of the crank angle, it may be specified as a failure of the gas fuel supply system, for example, a failure of the gas supply valve. it can. In this case as well, the failure location can be more reliably identified by adding a method of occurrence ratio in common parts of a plurality of cylinders.

  According to the present invention, it is possible to promptly cope with the problem by accurately identifying the cause of the failure from the occurrence state of abnormal combustion such as misfire, flame extinguishing, knocking, etc. determined based on the in-cylinder pressure detection value in the combustion chamber. An internal combustion engine failure cause estimation method and apparatus can be provided.

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

FIG. 1 shows an overall configuration of a failure cause estimating apparatus 3 for a gas engine 2 for a generator as an example of an internal combustion engine.
The gas engine 2 is a multi-cylinder four-cycle gas engine, a piston 6 fitted in the cylinder 4 so as to be slidable back and forth, and a crankshaft that converts the reciprocating motion of the piston 6 into rotation via a connecting rod 8. 10 is provided. The generator 11 is driven by the crankshaft 10.

  The gas engine 2 includes a combustion chamber 12 that is defined between the upper surface of the piston 6 and the inner surface of the cylinder 4, an air supply port 14 and an air supply pipe 16 that are connected to the combustion chamber 12, and the air supply port. 14 is provided with an air supply valve 18 for opening and closing 14, an exhaust port 20 connected to the combustion chamber 12, and an exhaust valve 22 for opening and closing the exhaust port 20.

In the middle of the air supply pipe 16, there is provided a gas injection device 24 for injecting fuel gas into air (supply air) flowing through the air supply pipe 16a and mixing it with air. A fuel gas supply pipe 26 is connected to the gas injection device 24 via a gas supply electromagnetic valve 28. The gas supply electromagnetic valve 28 is opened and closed by a control signal from a gas supply valve controller 30 to adjust the gas injection amount. The
The fuel gas and air premixed by the gas injection device 24 are supplied into the combustion chamber 12 through the supply port 14 and the supply valve 18.

  Further, an air supply reservoir 30 is provided upstream of the gas injection device 24, and air obtained by cooling the pressurized air from the supercharger 32 with an air cooler 34 is stored in the air reservoir 30. Air is supplied to the air supply pipes 16a, 16b, 16c. Further, in order to adjust the supply air pressure pressurized by the supercharger 32, a supply air release adjusting valve 36 is installed on the upstream side of the supply air reservoir 30, and is released to the atmosphere via the air supply discharge pipe 38. ing.

  A sub-chamber ignition device 40 is provided facing the combustion chamber 12, and is configured so that pilot fuel such as light oil is injected into the sub-chamber by the injection injector 42 to be ignited and combusted, and this combustion flame is ejected to the combustion chamber 12. Has been. A liquid fuel supply pipe 44a for supplying pilot fuel such as light oil is connected to the sub chamber ignition device 40, and the liquid fuel supply pipe 44a is supplied from a common rail 46 common to a plurality of cylinders. The pressure in the common rail 46 is kept constant, and the liquid fuel supply pipes 44a, 44b, 44c,... Of each cylinder are connected. The sub chamber ignition device 40 is controlled by a pilot valve controller 47 to control the injection timing and injection amount of pilot fuel.

  The main controller 48 controls the gas supply valve controller 30 according to engine operating conditions such as an engine speed input from a rotation detector (not shown) and an engine load input from the load detector 50 to control the gas supply electromagnetic valve 28. The gas injection amount is controlled by controlling the operation, and further, the pilot valve controller 47 is controlled to adjust the injection timing and the injection amount of the sub chamber ignition device 40.

The in-cylinder pressure of each cylinder 4 is measured by the in-cylinder pressure detector 52 installed in each cylinder 4 and input to the failure cause estimating device 54. Further, the detected value of the crank angle of the gas engine 2 detected by the crank angle detector 56 is inputted to the failure cause estimating device 54.
The failure cause estimation device 54 includes a first failure determination unit 58, a second failure determination unit 60, and a failure part estimation unit 62, and estimates the cause of the failure when a combustion state abnormality occurs. The failure cause estimation result is output to the display device 64 and to the main controller 48.

In the failure cause estimation device 54, the in-cylinder as shown in FIG. 4 is determined based on the in-cylinder pressure detection value input from the in-cylinder pressure detector 52 and the crank angle detection value input from the crank angle detector 56. A pressure P-crank angle θ relationship diagram is obtained.
In the in-cylinder pressure diagram shown in FIG. 4, A is normal combustion, B is knocking, C is misfired (compression only and no afterburning state), D is extinguished (not burning normally) Indicates the occurrence of afterburning.

(First embodiment)
With reference to FIG. 2, a first embodiment will be described in which the occurrence of extinguishing is in a first failure state and the occurrence of misfire is in a second failure state.
When starting at step S1, in step S2, the in-cylinder pressure data from the in-cylinder pressure detector 52 of the cylinder a and the crank angle detection data from the crank angle detector 56 are read for each combustion cycle. In step S3, the in-cylinder pressure ratio is read. to calculate the _{P 1} / P _0. This P ₀ represents the in-cylinder pressure at the crank angle θ ₀ (near the top dead center in the compression stroke) shown in the in-cylinder pressure diagram of FIG. 6, and P ₁ represents the crank angle θ ₁ (after the top dead center). The in-cylinder pressure at 10 ° to 15 °) is shown.
(In the above underline part, the crank angle position of P ₀ is set to the vicinity of the top dead center position. This is to align with the top dead center position of the air supply surging drop judgment position P ₀ of the second embodiment below.
Of _{P 0,} P _1, asks you for confirmation about the crank angle. )

  FIG. 7 is an in-cylinder pressure diagram showing a state in which flame extinction has occurred in a plurality of cylinders, and ignition is not performed normally and there is no rise in in-cylinder pressure, but the main fuel gas may self-ignite, After the crank angle is zero (near the top dead center in the compression stroke), a post-burning portion occurs in the P region of FIG. In the case of misfire, since there is no in-cylinder pressure portion such as the P region after burning, the occurrence of fire extinction and the occurrence of misfire can be distinguished.

Therefore, the calculated cylinder pressure ratio _P 1 / _{P 0} antiphlogistic occurrence determination threshold Pgn (e.g., a threshold of 1.3) as compared with the case of less than antiphlogistic occurrence determination threshold Pgn, the process proceeds to step S4 in Yes, in step S4 further compared with the misfire occurrence determination threshold Pen (e.g., a threshold of 1.1) using a cylinder pressure ratio _P 1 / _{P 0.}

If it is less than the misfire occurrence determination threshold Pen, it is determined that a misfire has also occurred in Yes. Then, the process proceeds to step S5 to calculate the misfire occurrence ratio in a plurality of cylinders. That is, it is determined whether or not the number of cylinders X that are extinguished and misfired exceeds the reference number of cylinders Xs (for example, 3 cylinders).
If the number of determination reference cylinders is exceeded, the process proceeds to step S6, and it is determined that a failure has occurred at a common part of a plurality of cylinders. It is considered that the occurrence of flame extinction and misfire is caused by a failure in the fuel gas supply system part. Therefore, in the case of a part common to a plurality of cylinders, it is estimated that the supply air release adjustment valve 36 and the gas supply valve controller 30 are abnormal.
If the number of determination reference cylinders is not exceeded in step S5, the process proceeds to step S7, where it is considered that the cylinder a alone has a failure. Therefore, the gas supply solenoid valve 28 is used as a part for each cylinder due to a failure in the fuel gas supply system. Estimated to be abnormal.

Furthermore, if the in-cylinder pressure ratio P ₁ / P ₀ is not less than the misfire occurrence determination threshold Pen in step S4, it is determined that only flame extinguishing has occurred, and the process proceeds to step S8 where flame extinguishing occurs in a plurality of cylinders. Calculate the percentage. That is, it is determined whether or not the number of extinguishing cylinders Y exceeds the determination reference cylinder number Ys (for example, 3 cylinders).

If the number of determination reference cylinders is exceeded, the process proceeds to step S9, where it is determined that a failure has occurred at a common part of a plurality of cylinders. Since the occurrence of the flame extinguishing state is considered to be a failure of the pilot fuel supply system part, in the case of a common part of a plurality of cylinders, it is estimated that the common rail 46 is abnormal and the pilot valve controller 47 is abnormal.
If the number of determination reference cylinders is not exceeded in step S8, the process proceeds to step S10, where it is considered that the cylinder a alone has a failure. Therefore, the sub-chamber ignition device 40 is used as a part for each cylinder due to a failure in the pilot fuel supply system. It is estimated that there is an abnormality in the internal injector 42.

Then, after estimating the cause of the abnormality, the process returns again in step S11 to determine the next combustion cycle.
The series of procedures for the cylinder a shown in steps S2 to S10 is performed in the same manner for the other cylinders such as the cylinder b and the cylinder c.

Further, regarding the determination of the occurrence of extinguishing in step S3 and the determination of the occurrence of misfire in step S4, FIG. 2 shows the determination for each cycle, but as shown in step S31 of FIG. The flame extinction occurrence rate (the number of extinction occurrences / a certain number of cycles, for example, 4 times / 10 cycles) of the flame extinction occurrence cycle in the case is obtained, and it is determined that the extinction has occurred when the extinction occurrence rate exceeds the set extinction rate Good.
Similarly, for the misfire determination, as shown in step S41 of FIG. 3, the misfire occurrence rate of the misfire occurrence cycle in the constant number of combustion cycles (number of misfire occurrences / number of constant cycles, for example, 4 times / 10 cycles) is obtained. When the misfire occurrence rate exceeds the misfire occurrence rate set value, it may be determined that misfire has occurred.

As described above, in the first embodiment, the location of the cause of failure is specified as long as the gas fuel of the main fuel is supplied from the supply pipe 16a, the ignition is normal even if the pilot fuel is not supplied from the sub-chamber ignition device 40. Is not performed, but the main fuel gas may self-ignite and become after-burning (flame extinguishment). In this case, it is determined that the pilot fuel is not sufficiently supplied to the sub chamber ignition device 40 instead of the main fuel gas supply system. Based on this idea, it can be presumed that the pilot fuel supply system has failed if the fire is not extinguished only by extinguishing the flame. Furthermore, if misfire has occurred, it can be assumed that the gas fuel itself is not supplied and that the main fuel gas supply system has failed.
In addition, when the occurrence ratio in a plurality of cylinders is greater than a certain level, it is further ensured that the faulty part is specified by estimating that the common part is faulty.

  According to the first embodiment, it is possible to reliably identify the cause of the failure depending on the occurrence of the flame extinction and the subsequent occurrence of misfire. The result can be displayed on the display device 64, reflected in the control of the main controller 48, and appropriate countermeasures can be taken.

(Second Embodiment)
Next, referring to FIG. 4, a second embodiment will be described in which knocking occurs in the first failure state and in-cylinder pressure drop near the crank angle top dead center in the compression stroke occurs in the second failure state. To do.
When the process starts in step S1, in-cylinder pressure data from the in-cylinder pressure detector 52 of the cylinder a and crank angle detection data from the crank angle detector 56 are read in every combustion cycle in step S2. a is the pressure P _P knocking allowable pressure P _K or more, cylinder pressure change rate [Delta] P / [Delta] [theta] is, determines that the knocking in the case of more cylinder pressure variation rate threshold I _k.

When it is determined that knocking has occurred, the process proceeds to step S54, and the in-cylinder pressure ratio P ₀ / P ₋₁ is calculated. This P ₀ represents the in-cylinder pressure at the crank angle θ ₀ (near the top dead center in the compression stroke) shown in the in-cylinder pressure diagram of FIG. 4, and P ₋₁ represents the crank angle θ ₋₁ (top dead center). The in-cylinder pressure at −15 ° to 20 °) is shown.
(In the above underline part, the crank angle position of P ₀ is set to the vicinity of the top dead center position. This is to align with the top dead center position of the air supply surging drop judgment position P ₀ of the second embodiment below.
Of _{P 0,} P _1, asks you for confirmation about the crank angle. )

When the in-cylinder pressure ratio P ₀ / P ₋₁ is less than the supply pressure drop threshold Pno, it is determined that sufficient pressure is not generated in the cylinder during the compression stroke.
FIG. 8 is an in-cylinder pressure diagram showing a state in which in-cylinder pressure drops due to supercharged air surging and knocking occurs in a plurality of cylinders, and is compared with a normal combustion diagram L1. In the diagram L2 in the case where the occurrence of the depression occurs, a depression is seen in the compression stroke top dead center region Q where the crank angle is substantially zero. The occurrence of the sag is determined by the supply pressure sag threshold Pno.

Then, the process proceeds to step S55, calculates the knocking and the ratio of the number of cylinders drop occurs in the P ₀ in multiple cylinders. That is, it is determined whether knocking and cylinder number Z of the drop in P ₀ exceeds the determination reference cylinder number Zs (e.g. 3 cylinder).

If the number of determination reference cylinders is exceeded, the process proceeds to step S56, and it is determined that a failure has occurred at a common part of a plurality of cylinders. Knocking occurs when the amount of air is reduced compared to the amount of gas in the main fuel and the gas fuel is in an excessive state. Further, P ₀ falls because of a failure in the air supply system including the supercharger 32. Therefore, in the case of a portion common to a plurality of cylinders, it is estimated that the supply surging due to the abnormal rotation of the supercharger 32 occurs.
If the number of determination reference cylinders is not exceeded in step S55, the process proceeds to step S57, and it is considered that the cylinder a alone has a failure. Therefore, it is estimated that the intake valve and exhaust valve of the cylinder a are abnormal.

Furthermore, if the in-cylinder pressure ratio P ₀ / P ₋₁ is not less than the supply air pressure drop threshold value Pno in step S54, it is determined that only knocking has occurred, and the process proceeds to step S58, in which a plurality of cylinders are used. Calculate the occurrence rate of knocking. That is, it is determined whether the number of knocking cylinders W exceeds the determination reference cylinder number Ws (for example, 3 cylinders).

If the number of determination reference cylinders has been exceeded, the process proceeds to step S59, where it is determined that a failure has occurred at a common part of a plurality of cylinders. Knocking occurs because the amount of air is reduced compared with the amount of gas of the main fuel and the gas fuel is considered to be in an excessive state. It is estimated that the gas supply valve controller 30 is abnormal.
On the other hand, if the number of determination reference cylinders is not exceeded in step S58, the process proceeds to step S60, where it is considered that the cylinder a alone has a failure.

  Then, after estimating the cause of the abnormality, the process returns again in step S61 to determine the next combustion cycle. The series of procedures for the cylinder a shown in steps S52 to S60 is performed in the same manner for the other cylinders such as the cylinder b and the cylinder c.

  As described above, the occurrence of the cause of failure in the second embodiment is specified because the occurrence of knocking occurs in a gas engine because the amount of air is reduced compared to the amount of main fuel gas and gas fuel is in an excessive state. Whether it is due to a gas system failure or a gas fuel supply system failure is determined by whether or not a drop in the in-cylinder pressure in the compression stroke occurs near the top dead center of the crank angle.

Therefore, if knocking occurs and the compression pressure drops near the top dead center of the crank angle, a sufficient amount of air is not secured for the fuel gas due to a failure of the air supply system, and the gas amount is reduced to air. It can be estimated that the number of
In addition, in the determination of the failure of the air supply system, if the occurrence rate in a plurality of cylinders is more than a certain value, it can be estimated that the failure is caused by a turbocharger failure of common parts, for example, supercharged air surging. Specificity is more certain.

  Also, if there is no further decrease in compression pressure near the top dead center of the crank angle, it is considered that gas fuel is being supplied excessively with respect to the amount of air. When the generation ratio in a plurality of cylinders exceeds a certain level, it is estimated that there is an abnormality in the common component air supply discharge adjustment valve 36 and the gas supply valve controller 30. If it is not a common part, it can be estimated that the cylinder-specific gas supply solenoid valve 28 has failed.

  According to the second embodiment, it is possible to reliably identify the cause of the failure by detecting the occurrence of knocking and the subsequent decrease in the in-cylinder pressure at the compression top dead center. The result can be displayed on the display device 64, reflected in the control of the main controller 48, and appropriate countermeasures can be taken.

Further, determination of knocking in the step S53, for the determination of the drop in cylinder pressure P ₀ in step S54, in FIG. 4, although the determination for each one cycle, as shown in step S531 of FIG. 5, When the extinction rate of the extinction occurrence cycle within a certain number of combustion cycles (the number of extinction occurrences / a constant number of cycles, for example, 4 times / 10 cycles) is obtained, and the extinction occurrence rate exceeds the set extinction rate, the occurrence of extinction You may judge.
Similarly, regarding the determination of the drop in the in-cylinder pressure P ₀ , as shown in step S541 in FIG. 5, the misfire occurrence rate of the misfire occurrence cycle (the number of misfire occurrences / the number of constant cycles, for example, 4 times / 10 cycles), and when the misfire occurrence rate exceeds the misfire occurrence rate set value, it may be determined that misfire has occurred.

Further, the pressure ratio was calculated using the detected values of the in-cylinder pressures P ₁ and P ₀ in the first embodiment and the in-cylinder pressures P ₀ and P ₋₁ in the second embodiment. _b like, taken intake valve 18 and exhaust valve 22 is opened air supply pressure criteria substantially identical compression start previous cylinder pressure and the pressure P _b, and the detection value P and the reference pressure P _b of the in-cylinder pressure Pressure difference ΔP (ΔP ₁ = P ₁ −P _b , ΔP ₀ = P ₀ −P _b , ΔP ₋₁ = P ₋₁ −P _b ) is made to correspond to the crank angle θ input from the crank angle detector 56. Of course, it may be calculated and used.

  According to the present invention, it is possible to promptly take corrective action by accurately identifying the cause of failure from the occurrence state of abnormal combustion such as misfire, extinguishing, knocking, etc. determined based on the in-cylinder pressure detection value in the combustion chamber. Therefore, it is useful when applied to a failure cause estimation method and apparatus for an internal combustion engine.

1 is an overall configuration diagram of a failure cause estimation apparatus for an internal combustion engine according to the present invention. It is an estimation control flowchart of the failure cause estimation device according to the first embodiment. It is an estimation control flowchart which shows the partial modification of 1st Embodiment. It is an estimation control flowchart of the failure cause estimation device according to the second embodiment. It is an estimation control flowchart which shows the partial modification of 2nd Embodiment. It is an in-cylinder pressure diagram of a gas engine. FIG. 6 is an in-cylinder pressure diagram showing a flame extinguishing state in a plurality of cylinders. It is a cylinder pressure diagram which shows the supply surging state in multiple cylinders.

Explanation of symbols

2 Gas Engine 4 Cylinder 10 Crankshaft 11 Generator 12 Combustion Chamber 26 Gas Supply Pipe 30 Supply Air Pool 32 Supercharger 36 Supply Air Release Control Valve 40 Subchamber Ignition Device 46 Common Rail 52 In-Cylinder Pressure Detector 54 Failure Cause Estimation Device 56 Crank angle detector 58 First failure determination means 60 Second failure determination means 62 Failure part estimation means

Claims (8)

In a method for estimating the cause of failure of an internal combustion engine including a gas engine configured to mix fuel gas with air and burn the fuel gas in a combustion chamber of the engine,
The in-cylinder pressure in the combustion chamber and the crank angle of the engine are detected, the first failure state is determined based on the in-cylinder pressure at a constant crank angle in the compression stroke and the combustion stroke, and at a crank angle different from the in-cylinder pressure. Pressure or in-cylinder pressure at the same crank angle, a second failure state is determined based on different criteria, and a failure cause is generated based on a combination of the occurrence of the first failure state and the occurrence of the second failure state A failure cause estimation method for an internal combustion engine, characterized by estimating a part.   2. The cause of failure of an internal combustion engine according to claim 1, wherein when the first failure state and the second failure state occur in a plurality of cylinders at a certain rate or more, a failure at a common part of the plurality of cylinders is estimated. Estimation method.   The internal combustion engine is a gas engine in which fuel gas is mixed with air and supplied to the combustion chamber of the engine, and pilot fuel is supplied to the sub-chamber igniter to ignite, and the first failure state is the occurrence of flame extinction. When the second failure state is the occurrence of misfire, the occurrence of flame extinction and the occurrence of misfire, it is presumed that the fuel gas supply system part to the combustion chamber is faulty. 2. The failure cause estimation method for an internal combustion engine according to claim 1, wherein the failure is estimated as a failure in a pilot fuel supply system part.   The internal combustion engine is a gas engine configured to mix fuel gas with supercharged air from a supercharger and supply the fuel gas to a combustion chamber of the engine, wherein the first failure state is knocking occurrence, and the second failure state Is a drop in the compression pressure near the top dead center of the crank angle. If the occurrence of knocking and a drop in the compression pressure near the top dead center occur, it is assumed that there is a failure in the supply system. 2. The method for estimating the cause of failure of an internal combustion engine according to claim 1, wherein if there is no drop in the compression pressure in the vicinity, it is estimated that the fuel gas supply system part has failed. In a failure cause estimation device for an internal combustion engine including a gas engine configured to mix fuel gas with air and burn the fuel gas in a combustion chamber of the engine,
An in-cylinder pressure detector for detecting an in-cylinder pressure in the combustion chamber and a crank angle detector for detecting a crank angle of the engine are provided, and a compression stroke from the in-cylinder pressure detector and the crank angle detector is provided. And a first failure determination means for determining a first failure state based on a detected value of the in-cylinder pressure at a constant crank angle during the combustion stroke, and a pressure different from the in-cylinder pressure or the same and different determination criteria. A second failure determination unit that determines a second failure state; and a failure part estimation unit that estimates an occurrence part of a failure cause based on a combination of occurrence of the first failure state and occurrence of the second failure state. An apparatus for estimating a cause of failure of an internal combustion engine.   6. The failure part estimation means estimates that a failure occurs in a common part of a plurality of cylinders when the first failure state and the second failure state occur in a plurality of cylinders at a certain rate or more. The failure cause estimation device for an internal combustion engine as described.   The internal combustion engine is a gas engine in which fuel gas is mixed with air and supplied to the combustion chamber of the engine, and pilot fuel is supplied to the sub-chamber igniter to ignite, and the first failure state is the occurrence of flame extinction. The second failure state is a misfire occurrence, and the failure site estimation means estimates that a failure has occurred in the fuel gas supply system to the combustion chamber in the case of the occurrence of a flame extinction and the occurrence of a misfire. 6. The failure cause estimation apparatus for an internal combustion engine according to claim 5, wherein if there is no occurrence, the failure is estimated to be a failure of the pilot fuel supply system part.   The internal combustion engine is a gas engine configured to mix fuel gas with supercharged air from a supercharger and supply the fuel gas to a combustion chamber of the engine, wherein the first failure state is knocking occurrence, and the second failure state Is a drop in the compression pressure near the top dead center of the crank angle, and the failure site estimation means estimates that the supply system has failed when knocking occurs and the compression pressure falls near the top dead center. 6. The failure cause estimation apparatus for an internal combustion engine according to claim 5, wherein if there is an occurrence and a drop in the compression pressure in the vicinity of the top dead center does not occur, it is estimated that the fuel gas supply system part has failed.

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