JP2009133284A - Combustion diagnostic method and combustion diagnostic device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a combustion diagnostic method and a combustion diagnostic device of an internal combustion engine capable of clearly identifying and determining preignition and abnormality of a pressure sensor in a cylinder, and with heightened reliability by detecting preignition in a cylinder in a wide load range regardless of an operating condition. <P>SOLUTION: In this combustion diagnosis method of an internal combustion engine (engine) for diagnosing a combustion condition in a cylinder based on an in-cylinder pressure detection value detected by an in-cylinder pressure detector, preignition is determined when a standard deviation σP<SB>α</SB>of a change of the in-cylinder pressure at a predetermined crank angle α before ignition of the engine is calculated and the standard deviation σP<SB>α</SB>is not less than a standard deviation threshold value β, and when a differential pressure ΔP<SB>0</SB>of the in-cylinder pressures at a reference crank angle and a top dead center is calculated and a load factor in-cylinder differential pressure ΔP<SB>0</SB>/L found by dividing the differential pressure ΔP<SB>0</SB>with a load factor L on a driven machine driven by the engine is not less than a load factor in-cylinder differential pressure threshold value γ. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a combustion diagnostic method and a combustion diagnostic apparatus for an internal combustion engine including a gas engine and a diesel engine, and particularly detects occurrence of pre-ignition in a cylinder in a wide load range without being influenced by an operation state. The present invention relates to an internal combustion engine combustion diagnostic method and a combustion diagnostic apparatus.

  In an internal combustion engine, particularly a gas engine that uses clean gas such as city gas as the main fuel, it is essential to detect and diagnose the combustion state in the combustion chamber, and to control the combustion ignition timing and the fuel injection amount in accordance with the combustion diagnosis result. At the same time, it can reliably detect malfunctions related to combustion such as occurrence of knocking due to misfire or extinguishing in the combustion chamber and non-uniform mixture concentration, or premature ignition due to residual unburned fuel in the cylinder. It is required to deal with the situation.

As diagnostic devices for detecting and diagnosing the combustion state in the combustion chamber of the engine, techniques such as Patent Document 1 (Japanese Patent Laid-Open No. 10-238374) and Patent Document 2 (Japanese Patent Laid-Open No. 2007-32407) have been proposed. ing.
In Patent Document 1, in a premixed ignition internal combustion engine in which fuel is supplied during intake and premixed, the ignition timing is appropriately controlled over a wide load range, and fuel is supplied during intake and premixed. By providing a premixed fuel injector and a compression ratio variable mechanism that varies the volume of the combustion chamber to vary the compression ratio, the compression ratio can be varied according to the amount of premixed fuel based on the load state. It is shown that control is performed so that self-ignition does not occur before the ignition timing even in such a load state.

  Patent Document 2 discloses a technique for performing a combustion diagnosis based on the in-cylinder pressure detection value. Whether or not pre-ignition has occurred is determined based on the pre-ignition threshold value in which the in-cylinder pressure is set in advance. Judgment is made based on the reference pressure value, and the abnormality determination logic of the in-cylinder pressure detector is stopped when premature ignition occurs, and the process proceeds to the abnormality determination logic of the in-cylinder pressure detector when premature ignition does not occur. This avoids misdiagnosis due to premature ignition cause mixing when determining the abnormality of the in-cylinder pressure detector, thereby preventing the occurrence of combustion diagnosis errors.

JP-A-10-238374 JP 2007-32407 A

Pre-ignition generally means that if an unburned ignition source such as high-temperature soot remains in the cylinder, the ignition source will start earlier than the original ignition point in the next cycle. This refers to the phenomenon of ignition and combustion. As shown in FIG. 6, ignition and combustion is performed earlier than the original ignition point (point F). With respect to normal in-cylinder pressure changes as indicated by A, B, C, and D, In-cylinder pressure changes such as A1, B1, C1, and D1 that have high pressure fluctuations.
For this reason, if pre-ignition progresses, the in-cylinder pressure increases. For example, in the case of a gas engine with a sub chamber, a serious trouble such as sub chamber damage occurs in the worst case. Some may damage the cylinder liner, collide with the exhaust valve, or invade and damage the turbocharger.

  Therefore, it is necessary to appropriately detect this pre-ignition and control the combustion. However, as a combustion diagnostic device for that purpose, the in-cylinder pressure before ignition at 15 ° to 40 ° before top dead center is detected and determined. Has been done.

However, with such a determination method, the detected value of the in-cylinder pressure at a specific crank angle before ignition is used to determine the abnormality of the in-cylinder pressure sensor that detects the in-cylinder pressure. Even if it is a sudden rise, there are many cases where it is erroneously determined that the sensor is abnormal, and when it is erroneously determined, the determination of sensor abnormality is given priority over other determinations. This determination is ignored, and the operation is continued under predetermined operating conditions. As a result, there is a problem that even if the pre-ignition phenomenon occurs due to ignition from the early stage of compression, it is determined that the sensor is abnormal and pre-ignition cannot be detected.
Furthermore, since the in-cylinder pressure characteristic changes depending on the engine load, detection of pre-ignition in a wide load range is insufficient without being influenced by the driving situation.

Therefore, it is necessary to distinguish between sensor abnormality determination and pre-ignition that are determined by detecting the in-cylinder pressure before ignition, and to make a reliable determination regardless of the operating state of the engine.
However, as described above, the technique of Patent Document 1 includes the premixed fuel injector and the compression ratio variable mechanism that makes the volume of the combustion chamber variable so that it does not self-ignite before the ignition timing in any load state. No means has been proposed for distinguishing between sensor abnormality determination and pre-ignition that are determined by detecting in-cylinder pressure before ignition.

  Further, as described above, the technique of Patent Document 2 has been shown to prevent the occurrence of a combustion diagnosis error by avoiding a misdiagnosis due to premature ignition cause mixing at the time of abnormality determination of the in-cylinder pressure detector. However, since the determination is based only on the in-cylinder pressure detection value at a predetermined crank angle, the determination according to the engine load is not taken into consideration, so that it is not sufficient for the determination in a wide load range regardless of the driving situation. It is.

  Therefore, the present invention has been made in view of such a background, and it is possible to clearly identify and determine the determination of premature ignition and the determination of abnormality of the in-cylinder pressure sensor. It is an object of the present invention to provide a combustion diagnostic method and a combustion diagnostic device for an internal combustion engine that can detect the occurrence of ignition in a wide load range without depending on the operation state and thereby improve the reliability.

In order to solve the above-mentioned problems, a first invention of the present application relates to a combustion diagnosis method for an internal combustion engine, and relates to an internal combustion engine that diagnoses a combustion state in a cylinder based on a detected value of a cylinder pressure detected by a cylinder pressure detector. In the combustion diagnosis method of (engine), the standard deviation (σP _α ) of the change in in-cylinder pressure at a predetermined crank angle (α) before ignition of the engine is calculated, and the standard deviation (σP _α ) is the standard deviation threshold (β) Thus, the differential pressure (ΔP ₀ ) of the in-cylinder pressure between the reference crank angle and the top dead center is calculated, and the differential pressure (ΔP ₀ ) is calculated as the load factor (L) on the driven machine side driven by the engine. When the load factor in-cylinder differential pressure (ΔP ₀ / L) divided by is equal to or greater than the load factor in-cylinder differential pressure threshold (γ), it is determined that pre-ignition has occurred.

According to this invention, the standard deviation (σP _α ) of the change in the in-cylinder pressure at the predetermined crank angle (α) before the ignition of the engine is calculated, and the standard deviation (σP _α ) is equal to or greater than the standard deviation threshold (β). In addition to this one determination condition, in addition to this condition, a differential pressure (ΔP ₀ ) of the in-cylinder pressure between the reference crank angle and the top dead center is calculated, and the differential pressure (ΔP ₀ ) is driven by the engine. Pre-ignition is determined by adding a second determination condition in which the load factor in-cylinder differential pressure (ΔP ₀ / L) divided by the machine-side load factor (L) is greater than or equal to the load factor in-cylinder differential pressure threshold (γ). To do.

By looking at the standard deviation (σP _α ) of the in-cylinder pressure at the predetermined crank angle (α) before the ignition of the engine according to the first determination condition, it is possible to determine abnormality of the in-cylinder pressure sensor. By adding, it can be distinguished from the in-cylinder pressure sensor that premature ignition has occurred, and in addition, the load factor (L) on the driven machine side is taken into consideration, so a determination in a wide engine load range is possible. It becomes possible.

As shown in FIGS. 4 and 5, FIG. 4 shows the in-cylinder pressure change situation at low load (50%), and FIG. 5 shows the in-cylinder pressure change situation at high load (80%). It can be seen that as the load increases, both ΔP ₀ and ΔPmax increase both during normal operation and during pre-ignition.
ΔP ₀ indicates the relative differential pressure between the in-cylinder pressure P _{−180 at} 180 ° before top dead center and the in-cylinder pressure P ₀ at the top dead center at zero crank angle, and ΔPmax is at 180 ° before top dead center. The relative pressure difference between the cylinder pressure P- ₁₈₀ and the cylinder maximum pressure Pmax is shown.
Therefore, in-cylinder pressure characteristics increase and decrease depending on the load, so that the determination of pre-ignition can suppress the influence of the engine load indicating the engine operating state as much as possible and make a determination in a wide load range. The in-cylinder pressure P ₀ at the top dead center and the relative differential pressure ΔP ₀ between the in-cylinder pressure P ₋₁₈₀ at the reference crank angle (180 ° before the dead center) divided by the load factor L ( (ΔP ₀ / L).
In this way, it is possible to determine in a wide load range without being influenced by the driving situation by dividing by the load factor.

Specifically, the load factor can be calculated using an actual power generation output with respect to a rated power generation output of a generator driven by the engine.
As described above, it is possible to clearly discriminate between the determination of pre-ignition and the determination of abnormality of the in-cylinder pressure sensor, and it is possible to determine the occurrence of pre-ignition in the cylinder without depending on the operation status, and a wide load range. And the reliability of the combustion diagnosis result of the internal combustion engine is increased.

Preferably, the determination above the standard deviation threshold (β) and the determination above the load factor in-cylinder differential pressure threshold (γ) are performed for each combustion cycle of the engine. It may be determined that pre-ignition occurs when the set number of occurrences occurs during the reference cycle.
Thus, the reliability of determination improves by determining with premature ignition when the case where both determination results are more than a threshold value occurs more than a set number of times.

In addition, it is preferable to determine that the in-cylinder pressure detector is abnormal when both the determinations do not occur more than a set number of times during the reference cycle number.
As described above, when there is a cycle in which both the determinations have not reached the set number but both the determinations are equal to or greater than the threshold value, it is determined that the in-cylinder pressure detector is abnormal. Judgment can be made separately from ignition.

Further preferably, when a ratio determined to be pre-ignition reaches a predetermined value or more within a predetermined time after the determination of pre-ignition, fuel to the cylinder determined to be pre-ignition is supplied. It is good to stop and make a cylinder resting state.
Thus, by comprehensively judging the result of a predetermined time, it is possible to reliably determine the cylinder in which the pre-ignition has occurred, and to take a countermeasure to make the cylinder resting operation state early. As a result, in a gas engine with a sub chamber, it is possible to prevent the occurrence of serious troubles such as sub chamber loss, and a part of the sub chamber that is damaged can damage the cylinder liner or collide with the exhaust valve. It is possible to avoid problems such as intrusion and damage to the turbocharger.

Further preferably, the engine is a gas engine, the driven machine is a generator, and the load factor (L) is determined from the ratio of the generator output of the generator to the rated power output of the generator. Should be calculated.
In a gas engine with a sub chamber, premixed gas fuel is drawn into the main combustion chamber from the intake valve, and combustion is propagated to the premixed gas fuel by a torch which is a fire type generated in the sub chamber. For this reason, if an unburned ignition source such as hot soot remains in the cylinder, the ignition source will be turned off when premixed gas is drawn into the main combustion chamber from the intake valve in the next cycle. Pre-ignition is likely to occur earlier than the original combustion as a starting point, but in the present invention such pre-ignition can be reliably determined over a wide load range by detecting the power generation output of the generator, and the sub chamber Can be prevented.

The second invention of the present application relates to a combustion diagnostic apparatus for an internal combustion engine for carrying out the combustion diagnostic method for an internal combustion engine of the first invention, and the in-cylinder pressure detection value detected by the in-cylinder pressure detector. An internal combustion engine (engine) combustion diagnostic apparatus for diagnosing a combustion state in a cylinder based on an in-cylinder pressure detection value from the in-cylinder pressure detector and a crank angle detection value from a crank angle detector. A standard deviation calculation unit for calculating a standard deviation (σP _α ) of a change in the cylinder pressure at a predetermined crank angle α before ignition, and whether or not the standard deviation (σP _α ) is equal to or greater than a standard deviation threshold (β). Based on the standard deviation determination unit for determining, the in-cylinder pressure detection value from the in-cylinder pressure detector and the crank angle detection value from the crank angle detector, the differential pressure between the in-cylinder pressure at the reference crank angle and the top dead center ( An in-cylinder differential pressure calculation unit for calculating ΔP ₀ ), and a load factor in-cylinder differential pressure (ΔP ₀ //) obtained by dividing the differential pressure (ΔP ₀ ) by a load factor (L) on the driven machine driven by the engine. L) is a load factor in-cylinder differential pressure threshold (γ) or more, and the standard deviation (σP _α ) is set to a standard deviation threshold ( β) or more, and when the load factor in-cylinder differential pressure determining means determines that the load factor in-cylinder differential pressure (ΔP ₀ / L) is greater than or equal to the load factor in-cylinder differential pressure threshold (γ), An early ignition determination unit that determines excessive ignition is provided.

According to such an invention, the standard deviation calculation unit performs the predetermined crank angle (α) before ignition of the engine based on the in-cylinder pressure detection value from the in-cylinder pressure detector and the crank angle detection value from the crank angle detector. The standard deviation (σP _α ) of the change in in-cylinder pressure is calculated, and the in-cylinder pressure differential pressure (ΔP ₀ ) between the reference crank angle and the top dead center is calculated by the engine by the load factor in-cylinder differential pressure determination unit. The in-cylinder differential pressure (ΔP ₀ / L) divided by the load factor (L) of the driven machine to be driven is calculated, and the standard deviation (σP _α ) and the in-cylinder load factor are calculated by the pre-ignition determination unit. When both of the differential pressures (ΔP ₀ / L) are equal to or greater than the threshold value, it is determined as premature ignition. Therefore, it is possible to clearly identify and determine the premature ignition determination and the in-cylinder pressure sensor abnormality determination. , The occurrence of premature ignition in the cylinder It allows detection over a wide load range without being influenced, increases the reliability of the combustion diagnosis result of the internal combustion engine.

  In the apparatus invention, preferably, the standard deviation determination unit has a standard deviation threshold (β) or higher determination, and the load factor in-cylinder differential pressure determination unit has a load factor in-cylinder differential pressure threshold (γ) or higher. The determination is performed for each combustion cycle of the engine, and the pre-ignition determination unit determines pre-ignition when both of the determinations occur more than a set number of times in the reference cycle number, and both determination results However, when the number of times equal to or greater than the threshold value does not occur more than the set number of times during the reference cycle number, it is preferable to determine that the in-cylinder pressure detector is abnormal.

Thus, the reliability of determination improves by determining with premature ignition when the case where both determination results are more than a threshold value occurs more than a set number of times.
If there is a cycle in which both the determinations have not reached the set number of times but both the determinations are equal to or greater than the threshold value, it is determined that the in-cylinder pressure detector is abnormal, thereby detecting the abnormality in the in-cylinder pressure detector and premature ignition. It is possible to make a distinction.

Preferably, the apparatus invention further includes an operation control means for controlling the operation of the engine, and the operation control means outputs a determination result from the pre-ignition determination unit that the pre-ignition is determined at a constant rate within a predetermined time. When the above is received, it is preferable to stop the fuel to the cylinder determined to be prematurely ignited so that the cylinder is rested.
According to such an invention, the operation control means can reliably determine the cylinder in which the premature ignition has occurred, and can appropriately take a countermeasure for making the cylinder resting operation state early.

Preferably, in the apparatus invention, the engine is a gas engine, the driven machine is a generator, the power generation output of the power generator is detected, and the load is calculated from a ratio with the rated power output of the power generator. A load factor calculating means for calculating the rate (L) may be provided.
In such an invention, the load factor calculating means can detect the power generation output of the generator and calculate the load factor (L) from the ratio with the rated power generation output of the generator, so that pre-ignition can be reliably performed in a wide load range. Can be judged.

  According to the present invention, the determination of pre-ignition and the determination of abnormality of the in-cylinder pressure sensor can be clearly identified and determined, and the occurrence of pre-ignition in the cylinder is not affected by the driving situation, and a wide load It is possible to provide a combustion diagnostic method and combustion diagnostic apparatus for an internal combustion engine that can be detected in a range and have improved reliability.

  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.

The drawings referred to in the description of the embodiment are as follows.
FIG. 1 is a control flowchart of a combustion diagnostic apparatus according to an embodiment of the present invention. FIG. 2 is an overall configuration diagram illustrating a combustion diagnosis apparatus for a gas engine according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing the in-cylinder pressure change situation at the time of premature ignition. FIG. 4 is an explanatory diagram showing the in-cylinder pressure change state between when pre-ignition occurs at low load and when it is normal. FIG. 5 is an explanatory diagram showing the in-cylinder pressure change state between the occurrence of premature ignition under a high load and the normal time. FIG. 6 is an explanatory diagram showing the in-cylinder pressure change situation of premature ignition of the gas engine.

FIG. 2 is a configuration diagram showing the overall configuration of the gas engine combustion diagnostic apparatus 40 according to the embodiment of the present invention.
In FIG. 2, the gas engine 2 is a multi-cylinder four-cycle gas engine. A crankshaft 10 is provided.
The gas engine 2 includes a combustion chamber 12 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 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.

A gas mixer 24 is installed in the middle of the air supply pipe 16. The fuel gas supplied from the fuel gas pipe 26 through the gas amount adjusting valve 28 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 24, and this premixed gas is supplied to the combustion chamber 12 through the supply port 14 and the supply valve 18.
The ignition device 30 is composed of a pilot injection device that injects a pilot fuel 32 such as light oil into an auxiliary chamber (not shown) by an injection nozzle 34 to ignite and combust it, and injects the combustion flame into the combustion chamber 12.

The fuel control device 36 controls the opening or opening time of the gas amount adjusting valve 28 and also controls the operation of the gas engine by controlling the supply of the pilot fuel 32 to the injection nozzle 34.
In-cylinder in-cylinder pressure of the gas engine 2 is measured by an in-cylinder pressure detector (in-cylinder pressure sensor) 38 and input to the combustion diagnostic device 40.
Further, the detected value of the crank angle of the gas engine 2 detected by the crank angle detector 42 is input to the combustion diagnostic device 40.

  As for the engine load of the gas engine 2, the power generated by the generator 44 driven by the gas engine 2 is input to the combustion diagnostic device 40 as a load signal. Of course, even if the generator 44 is not installed, a load detector may be attached to the crankshaft 10 to detect the engine load.

The combustion diagnostic device 40 includes pre-ignition determination means 46 and operation control means 48. The pre-ignition determination means 46 further includes an in-cylinder pressure detection value from the in-cylinder pressure detector 38 and a crank angle detector. 42, a standard deviation calculator 50 for calculating a standard deviation σP _α of a change in the in-cylinder pressure at a predetermined crank angle α before ignition of the engine based on the detected crank angle value from 42, and the standard deviation σP _α is equal to or greater than the standard deviation threshold β Based on the standard deviation determination unit 52 for determining whether or not, the in-cylinder pressure detection value from the in-cylinder pressure detector 38 and the crank angle detection value from the crank angle detector 42, and the top dead center cylinder in-cylinder pressure calculation unit 54 for calculating a differential pressure [Delta] P ₀ pressure, load factor-cylinder differential pressure [Delta] P obtained by dividing the load factor L of the generator 44 which is driven differential pressure [Delta] P ₀ by the engine in a ₀ / L is load And the load factor-cylinder pressure difference determination unit 56 is equal to or larger cylinder difference pressure threshold gamma, with standard deviation .sigma.p _alpha to determine the standard deviation threshold β or more, the load factor-cylinder differential pressure [Delta] P ₀ It is configured to include an pre-ignition determination unit 58 that determines whether / L is equal to or greater than the load factor in-cylinder differential pressure threshold γ and determines pre-ignition of the engine, and a load factor calculation unit 60.
Further, the operation control means 48 controls the fuel control device 36 to control the fuel gas amount by supplying the pilot fuel 32 to each cylinder and controlling the gas amount adjusting valve 28.

Next, control of the pre-ignition determination by the combustion diagnostic device 40 will be described based on FIG.
The control flow in FIG. 1 is performed for each combustion cycle of the gas engine 2, and the combustion state for each cycle is determined by steps S1 to S5 in FIG.
Then, based on the determination result of the instantaneous pre-ignition of each cycle, comprehensive determination is performed in steps S6 to S10, and the operation control of the gas engine is performed based on the result. That is, steps S1 to 5 are referred to as instantaneous determination, and steps S6 to S10 are referred to as comprehensive determination. This instantaneous determination is performed by the pre-ignition determination means 46, and the comprehensive determination is performed by the operation control means 48.

First, starting at step S1, in step S2, the standard deviation calculator 50 determines the engine 2 based on the in-cylinder pressure detection value from the in-cylinder pressure detector 38 and the crank angle detection value from the crank angle detector 42. A standard deviation σP ₋₄₀ of a change in in-cylinder pressure at a predetermined crank angle α before ignition, for example, 40 degrees before top dead center is calculated. A control flow is executed for each combustion cycle, and the standard deviation σP- ₄₀ is determined by, for example, the standard deviation in 16 cycles.
The standard deviation determination unit 52 determines whether or not the standard deviation σP- ₄₀ of the change in the in-cylinder pressure at 40 degrees before the top dead center is a standard deviation threshold β, for example, 0.1 or more. If the standard deviation σP- ₄₀ is greater than or equal to the standard deviation threshold β = 0.1, the process proceeds to the next step S3, and if it does not exceed 0.1, the process proceeds to step S9, and to other knocking determination or misfire determination. Proceed with

The change state of the in-cylinder pressure at 40 degrees before the top dead center is shown in FIG. As can be seen from this change characteristic, the in-cylinder pressure changes suddenly as shown in the H region of FIG. 3 due to the occurrence of premature ignition. The change in the in-cylinder pressure due to the occurrence of this pre-ignition is detected by calculating the standard deviation σP- _40, and is used as a determination factor.

The reason why the temperature is set to 40 degrees before the top dead center is that the ignition timing of the gas engine is about 10 degrees to 20 degrees before the top dead center. It was.
In addition, for the standard deviation threshold β of 0.1, a bench test is performed in advance with the same model engine, and an engine in which pre-ignition has occurred and an engine in which pre-ignition has not occurred are compared. In the case of this embodiment in which a standard deviation threshold is set in advance, β = 0.1 is set from the test result. An example of the test results is shown in Table 1.

As can be seen from Table 1, when the premature ignition occurs, the standard deviation σP- ₄₀ varies as much as 10 times or more in the standard deviation. In this embodiment, the standard deviation σP- ₄₀ is reliably determined by setting to 0.1. be able to.

Next, the process proceeds to step S3 in the flowchart of FIG. 1, and the in-cylinder differential pressure calculation unit 54 determines the in-cylinder pressure detection value from the in-cylinder pressure detector 38 and the crank angle detection value from the crank angle detector 42. A differential pressure ΔP ₀ = P ₀ −P ₋₁₈₀ between the reference crank angle, the in-cylinder pressure P _{−180 at} 180 degrees before the top dead center, and the in-cylinder pressure P ₀ at the top dead center is calculated.
Then, a load factor in-cylinder differential pressure ΔP ₀ / L obtained by dividing the calculated differential pressure ΔP ₀ by the engine load, that is, the load factor L of the generator 44 on the driven machine driven by the gas engine 2 is obtained. The load factor L is calculated from the ratio of the actual generated power to the rated power output of the generator 44.

Then, the load factor in-cylinder differential pressure determination unit 56 determines whether or not the load factor in-cylinder differential pressure ΔP ₀ / L is a load factor in-cylinder differential pressure threshold γ, for example, 20 or more. If the load factor in-cylinder differential pressure ΔP ₀ / L is greater than or equal to the load factor in-cylinder differential pressure threshold γ = 20, the process proceeds to the next step S4, and if it does not exceed 20, the process proceeds to step S8. Judged as abnormal.

  For the load factor in-cylinder differential pressure threshold γ = 20, a bench test is performed in advance, and a threshold is set by comparing an engine in which pre-ignition has occurred with an engine in which pre-ignition has not occurred. In the case of the form, γ = 20 was set from the test result. An example of the test results is shown in Table 1 above. As can be seen from the results of Table 1, the load factor in-cylinder differential pressure threshold γ is found to exceed 20 when premature ignition occurs, so if it is 20 or more, it is determined that premature ignition has occurred. can do.

Next, the process proceeds to step S4 in the flowchart. When the determination result in step S3 is YES in the pre-ignition determination unit 58, that is, the condition A that the load factor in-cylinder differential pressure threshold γ is 20 or more is satisfied. Is determined whether the number of occurrences of this YES has reached the set number N.
Since the control routine is determined for each combustion cycle, for example, 10 cycles are set as the determination reference block, and it is determined whether the determination of YES has reached, for example, 4 times during the 10 cycles. If it has reached, it is determined in step S5 that pre-ignition has occurred, and if the determination of YES has not reached four times, the process proceeds to step S8 where it is determined that the in-cylinder pressure sensor 38 is abnormal.

Thus, since the pre-ignition is determined when the determination of YES in step 3 reaches four times during 10 cycles, the reliability of the determination is improved.
In addition, if there is a cycle in which both of the determinations are equal to or greater than the threshold value, the abnormality of the in-cylinder pressure sensor 38 is determined to be abnormal by determining that the in-cylinder pressure sensor 38 is abnormal. It is possible to distinguish the judgment from ignition.

  Next, proceeding to step S6, the operation control means 48 receives the determination result of premature ignition from step S5, and then determines the result of premature ignition from step S5 for a set time T, for example, 5 to 13 seconds. To calculate the pre-ignition ratio. When the calculated ratio is equal to or greater than the set reference value P = 60%, the process proceeds to step S7, and pre-ignition is determined as the final determination result of the combustion state of the gas engine 2.

As a result, the operation control means 48 sends a signal for stopping the supply of the gas fuel to the cylinder to be determined to the fuel control device 36 so as to put the target cylinder in a cylinder deactivation state. Then, the process ends at step S10 and returns.
As described above, the determination of pre-ignition is comprehensively made based on the ratio of the determination result of pre-ignition within the set time T, for example, 5 to 13 seconds. Appropriate measures for setting the cylinder operating state can be taken.

  In step S6, if the pre-ignition occupancy ratio does not reach the set reference value P = 60%, for example, the process proceeds to step S8, where it is determined that the in-cylinder pressure sensor 38 is abnormal, and the process ends in step S10 and returns. . When the abnormality of the in-cylinder pressure sensor 38 is determined in step S8, the fuel supply is not stopped and the operation is maintained under the predetermined operation conditions.

According to the control flow of the above embodiment, the standard deviation σP- ₄₀ of the in-cylinder pressure at 40 degrees before top dead center corresponding to before the ignition of the engine in step S2 is compared with the standard deviation threshold value of 0.1, Abnormality of the in-cylinder pressure sensor 38 can be determined, and further, in step 3, the load factor in-cylinder differential pressure ΔP ₀ / L is further compared with the load factor in-cylinder differential pressure threshold value 20 to detect the occurrence of premature ignition. It can be determined, and it can be determined that pre-ignition has occurred, distinctly from the abnormality of the in-cylinder pressure sensor 38.

Furthermore, considering the load factor L of the generator 44, which is the engine load, the load factor in-cylinder differential pressure ΔP ₀ / L is newly set as a determination factor, and the value is used as an evaluation factor for determination. It is possible to provide a highly reliable combustion diagnostic method and combustion diagnostic apparatus for an internal combustion engine by enabling determination in a wide load range regardless of the situation.

  According to the present invention, the determination of pre-ignition and the determination of abnormality of the in-cylinder pressure sensor can be clearly identified and determined, and the occurrence of pre-ignition in the cylinder is not affected by the driving situation, and a wide load It is possible to provide a combustion diagnostic method and combustion diagnostic apparatus for an internal combustion engine that can be detected in a range and have improved reliability, which is advantageous when applied to a combustion diagnostic apparatus for a gas engine.

It is a control flowchart of the combustion diagnostic apparatus of embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram showing a combustion diagnosis device for a gas engine that shows an embodiment of the present invention. It is explanatory drawing which shows the cylinder pressure change condition at the time of premature ignition. It is explanatory drawing which describes the in-cylinder pressure change situation at the time of premature ignition generation | occurrence | production at the time of low load, and normal time. It is explanatory drawing which describes the in-cylinder pressure change situation at the time of premature ignition generation | occurrence | production at the time of high load, and normal time. It is explanatory drawing which describes the cylinder pressure change condition of the premature ignition generation | occurrence | production of a gas engine.

Explanation of symbols

2 Gas engine (engine)
10 Crankshaft 36 Fuel control device 38 In-cylinder pressure sensor (in-cylinder pressure detector)
DESCRIPTION OF SYMBOLS 40 Combustion diagnostic apparatus 42 Crank angle detector 44 Generator 46 Pre-ignition determination means 48 Operation control means 50 Standard deviation calculation part 52 Standard deviation determination part 54 In-cylinder differential pressure calculation part 56 Load factor In-cylinder differential pressure determination part 58 Excessive Early ignition determination unit 60 Load factor calculation unit

Claims (10)

In the combustion diagnosis method for an internal combustion engine (engine) for diagnosing the combustion state in the cylinder based on the in-cylinder pressure detection value detected by the in-cylinder pressure detector,
The standard deviation (σP _α ) of the change in in-cylinder pressure at a predetermined crank angle (α) before the ignition of the engine is calculated, and the standard deviation (σP _α ) is equal to or greater than the standard deviation threshold (β) and above the reference crank angle. The in-cylinder pressure differential pressure (ΔP ₀ ) with respect to the dead point is calculated, and the differential pressure (ΔP ₀ ) is divided by the load factor (L) on the driven machine driven by the engine. A combustion diagnosis method for an internal combustion engine, wherein it is determined that pre-ignition has occurred when (ΔP ₀ / L) is equal to or greater than a load factor in-cylinder differential pressure threshold value (γ).   The determination above the standard deviation threshold (β) and the determination above the load factor in-cylinder differential pressure threshold (γ) are performed for each combustion cycle of the engine. 2. The combustion diagnosis method for an internal combustion engine according to claim 1, wherein pre-ignition is determined when the occurrence occurs more than a set number of times.   3. The combustion diagnosis method for an internal combustion engine according to claim 2, wherein when both of the determinations do not occur more than a set number of times during the reference cycle number, a determination is made that the in-cylinder pressure detector is abnormal. .   When the ratio determined to be premature ignition reaches a predetermined value or more within a predetermined time after the determination of premature ignition, the fuel to the cylinder determined to be premature ignition is stopped and the cylinder is stopped. The combustion diagnosis method for an internal combustion engine according to claim 2, wherein the combustion state is set to an operating state.   The engine is a gas engine, the driven machine is a generator, and the load factor (L) is calculated from a ratio with the rated power output of the generator by detecting the power generation output of the generator; The combustion diagnosis method for an internal combustion engine according to claim 1, characterized in that: In a combustion diagnostic apparatus for an internal combustion engine (engine) for diagnosing a combustion state in a cylinder based on a cylinder pressure detection value detected by a cylinder pressure detector,
Based on the in-cylinder pressure detection value from the in-cylinder pressure detector and the crank angle detection value from the crank angle detector, the standard deviation (σP _α ) of the change in in-cylinder pressure at a predetermined crank angle α before ignition of the engine is calculated. A standard deviation calculation unit to calculate,
A standard deviation determination unit for determining whether or not the standard deviation (σP _α ) is equal to or greater than a standard deviation threshold (β);
A cylinder for calculating a differential pressure (ΔP ₀ ) between the reference crank angle and the top dead center based on the in-cylinder pressure detection value from the in-cylinder pressure detector and the crank angle detection value from the crank angle detector. An internal differential pressure calculator,
The load factor in-cylinder differential pressure (ΔP ₀ / L) obtained by dividing the differential pressure (ΔP ₀ ) by the load factor (L) on the driven machine driven by the engine is equal to or greater than the load factor in-cylinder differential pressure threshold (γ). A load factor in-cylinder differential pressure determination unit that determines whether or not
The standard deviation determining means determines that the standard deviation (σP _α ) is equal to or greater than a standard deviation threshold (β), and the load factor in-cylinder differential pressure determining means determines the load factor in-cylinder differential pressure (ΔP ₀ / L) as a load factor. An internal combustion engine combustion diagnostic apparatus comprising: an early ignition determination unit that determines whether the engine is prematurely ignited when it is determined that the pressure difference is in-cylinder differential pressure threshold (γ) or more.   The determination that the standard deviation determination unit is greater than or equal to the standard deviation threshold value (β) and the determination that is greater than or equal to the load factor in-cylinder differential pressure threshold value (γ) are performed for each combustion cycle of the engine. 7. The internal combustion engine according to claim 6, wherein the pre-ignition determination unit determines pre-ignition when both of the determinations occur more than a set number of times in the reference cycle number. Combustion diagnostic device.   The pre-ignition determination unit determines that the in-cylinder pressure detector is abnormal when the number of times that both the determinations are equal to or greater than the threshold value does not occur more than the set number of times during a reference cycle number. A combustion diagnostic apparatus for an internal combustion engine as described.   An operation control means for controlling the operation of the engine, and the operation control means receives the pre-ignition from the pre-ignition determination unit when the pre-ignition is received at a predetermined ratio or more within a predetermined time. 8. The combustion diagnosis apparatus for an internal combustion engine according to claim 7, wherein the determined fuel is stopped and the cylinder is rested.   The engine is a gas engine, the driven machine is a generator, a load factor for detecting the power generation output of the generator and calculating the load factor (L) from a ratio with the rated power generation output of the generator 7. A combustion diagnostic apparatus for an internal combustion engine according to claim 6, further comprising a calculating means.

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