JP2013032726A - Abnormality diagnostic device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality diagnostic device for an internal combustion engine capable of accurately and quantitatively computing a heat load applied on a combustion chamber component part based on actual in-combustion chamber pressure data and the like.SOLUTION: The abnormality diagnostic device for the internal combustion engine includes an in-cylinder pressure sensor for detecting pressure in a combustion chamber, a crank angle sensor for detecting an angle of a crank shaft for actuating a piston, a supply air temperature sensor for detecting temperature of supply air supplied into the combustion chamber, a supply air pressure sensor for detecting pressure of the supply air, and a computing means. The computing means has: a storage part for storing specification data for the internal combustion engine as a diagnosis target, physical properties of combustion gas, pressure in the combustion chamber, a crank angle, supply air temperature, and supply air pressure; and a computing part for determining an index relatively indicating the magnitude of heat flux between combustion gas in the combustion chamber and a combustion chamber wall surface, and comparing the index with a predetermined reference value to determine presence/absence of abnormality of a cylinder unit comprising the internal combustion engine on the basis of the data stored in the storage part.

Description

  The present invention relates to an abnormality diagnosis apparatus for an internal combustion engine, and more particularly to an apparatus for diagnosing a cylinder condition before occurrence of an abnormality based on actual cylinder pressure data and the like.

  As a method for diagnosing abnormalities in an internal combustion engine, a method for detecting deterioration of so-called cylinder conditions such as abnormal wear, scuffing, cracks, burnout, etc. of combustion chamber components such as cylinder liners, pistons, piston rings, exhaust valves, etc. There are methods such as mist detector and cylinder liner temperature measurement. However, any of these methods can be detected only after an abnormality occurs.

  On the other hand, there is also an abnormality diagnosis device that performs abnormality diagnosis based on in-cylinder pressure data (combustion chamber pressure data), etc., and detects the risk of causing damage or deterioration of combustion chamber components and performance deterioration. . In such a device, for example, permissible values are set empirically for each engine for data such as pressure in the combustion chamber, fuel injection amount, torque, and exhaust gas temperature, and the presence or absence of abnormality is diagnosed based on this permissible value. It is to do.

  Examples of such an abnormality diagnosis device include those disclosed in Patent Documents 1 to 4. The device disclosed in Patent Document 1 obtains the indicated torque from the calculation based on the in-cylinder pressure sensor, and diagnoses the presence or absence of an abnormality in the fuel injection system from the indicated torque value.

  The apparatus disclosed in Patent Document 2 detects the pressure in the combustion chamber and the crank angle, and calculates the differential pressure between the detected pressure in the combustion chamber and the reference pressure in correspondence to each crank angle. Then, the combustion chamber pressure ratio between the differential pressure at each crank angle and the differential pressure at an arbitrary crank angle is obtained, and knocking, misfire, flame extinction, excessive increase in the pressure in the combustion chamber, etc. are diagnosed based on this value. It is.

  Further, the device disclosed in Patent Document 3 is based on the pressure difference between the average value of the reference in-cylinder pressure (combustion chamber pressure) detected by the in-cylinder pressure detector and the reference in-cylinder pressure. The combustion state is diagnosed.

  Further, the device disclosed in Patent Document 4 estimates or detects the input or output of the internal combustion engine, and corrects the throttle opening, fuel injection pulse width, fuel injection timing, ignition timing, exhaust gas recirculation amount, and the like. A correction device for performing the above is provided, and a fuel consumption is evaluated by recording a correction amount every predetermined time by the correction device. Then, abnormality determination is performed by the abnormality diagnosis means based on the fuel consumption.

JP 2006-138293 A JP 2007-170405 A JP 2007-23781 A JP 2007-303426 A

  However, in recent years, deterioration of cylinder conditions often occurs due to an increase in output rate, changes in fuel properties, aging of parts, and the like, and there are many cases where follow-up measures are followed.

In particular, problems related to tribology make it difficult to identify the cause because there are a variety of influencing factors such as mechanical load, thermal load, fuel properties, lubrication conditions, material characteristics, and surface roughness. For this reason, considerable time and cost may be required to investigate the cause and take measures to solve the problem.
One of the main causes of the deterioration of the cylinder condition is a thermal load caused by combustion gas.

  However, as described above, the conventional abnormality diagnosis technique for diagnosing this heat load is to perform abnormality diagnosis based on data such as pressure in the combustion chamber, fuel injection amount, torque, exhaust gas temperature, etc. It is not an indicator that can be done, and it is not accurate enough. For this reason, the actual condition is that the deterioration of the cylinder condition, in particular, accidental damage related to tribology, etc., will not stop.

  Of course, the deterioration of the cylinder condition may be caused by factors other than heat load. For example, catalyst particles used during oil production may remain in the fuel, causing abnormal wear of cylinder liners, piston rings, injection valves, etc. However, this has a very clear cause and is easy to take countermeasures.

  In the present invention, based on actual cylinder pressure data (combustion chamber pressure data) and the like, the heat load applied to the combustion chamber component is accurately and quantitatively calculated and diagnosed, and the heat of the combustion chamber component due to the combustion gas is calculated. An object of the present invention is to provide an internal combustion engine abnormality diagnosis device that prevents deterioration of cylinder conditions caused by a load.

  In order to achieve the above object, an abnormality diagnosis apparatus for an internal combustion engine according to the present invention includes an in-cylinder pressure sensor that detects a pressure in a combustion chamber, a crank angle sensor that detects an angle of a crankshaft that operates a piston, and the combustion An air supply temperature sensor for detecting an air supply temperature supplied to the room, an air supply pressure sensor for detecting the pressure of the air supply, and an arithmetic means, wherein the arithmetic means is an internal combustion engine to be diagnosed. Specification data, physical properties of combustion gas, combustion chamber pressure detected by the cylinder pressure sensor, crank angle detected by the crank angle sensor, supply air temperature detected by the supply air temperature sensor, and supply air pressure Based on the data stored in the storage unit, the storage unit storing the supply air pressure detected by the sensor, between the combustion gas in the combustion chamber and the combustion chamber wall surface An index that relatively represents the magnitude of the heat flux is calculated, and the calculation unit that compares the index with a previously determined reference value to determine whether there is an abnormality in units of cylinders that constitute the internal combustion engine, It is characterized by having.

  Further, in the abnormality diagnosis device for an internal combustion engine having the above-described characteristics, the arithmetic unit calculates the average of the indices obtained for each cylinder at the time of the first determination after the first determination of determining whether there is an abnormality in each cylinder. It is preferable to compare the average index as a value with the index and perform the second determination for determining whether there is an abnormality in each cylinder constituting the internal combustion engine.

  By performing the diagnosis in this way, the absolute value diagnosis for each cylinder is performed in the first determination, and the variation diagnosis between the cylinders is performed in the second determination, thereby improving the accuracy of abnormality detection as the internal combustion engine. Can do.

  Further, in the abnormality diagnosis apparatus for an internal combustion engine having the above-described characteristics, the calculation unit obtains the index by a function including a term determined based on a pressure value and a term determined based on a temperature. Good.

  With this configuration, the heat flux between the combustion chamber and the wall surface in the internal combustion engine that is substantially difficult to calculate can be relatively represented by a function determined based on the pressure value and the temperature.

Further, in the abnormality diagnosis apparatus for an internal combustion engine having the above-described characteristics, the function is a value representing a relative value of the heat flux at the crank angle at the combustion start timing in each cylinder, and the heat flux at the combustion end timing. A function for obtaining an integrated value up to a value relatively representing the magnitude, or an accumulated value of a value relatively representing the magnitude of the heat flux during one rotation of the crankshaft is preferable.
By using the function configured in this way, it is possible to obtain a quantitative value with little variation for each measurement. Therefore, the accuracy of abnormality diagnosis can be improved.

  Further, in the abnormality diagnosis apparatus for an internal combustion engine having the above-described characteristics, the function is a value representing a relative value of the heat flux at the crank angle at the combustion start timing in each cylinder, and the heat flux at the combustion end timing. It may be a function for obtaining an average value up to a value relatively representing the magnitude, or an average value of values relatively representing the magnitude of the heat flux during one rotation of the crankshaft.

  Even when a function configured in this way is used, a quantitative value with little variation for each measurement can be obtained. Therefore, the accuracy of abnormality diagnosis can be improved.

Further, in the first determination, the calculation unit obtains a difference between the exponent and a reference value obtained in advance, and is normal when the difference is within a predetermined first threshold range, When the difference is not within the range of the first threshold value, it may be determined as abnormal.
By performing such a diagnosis, an absolute value diagnosis for each cylinder can be performed.

Further, in the second determination, the calculation unit obtains a difference between the average index and the index obtained for each cylinder, and the difference is within a predetermined second threshold range. It is desirable to determine that the abnormality is normal and the difference is not within the second threshold range.
By performing such a diagnosis, it is possible to detect an abnormality based on the variation between the cylinders that may cause a detection failure in the absolute value diagnosis.

  According to the abnormality diagnosis apparatus for an internal combustion engine having the above-described features, it is possible to accurately and quantitatively calculate the heat load applied to the combustion chamber components based on actual combustion chamber pressure data and the like. Then, by performing abnormality diagnosis based on the index related to the heat load, it is possible to accurately detect the abnormal state. That is, it is possible to prevent the deterioration of the cylinder condition due to the thermal load of the combustion chamber components due to the combustion gas.

It is a block diagram which shows the structure of the internal combustion engine which concerns on embodiment, and an abnormality diagnosis apparatus. It is a flowchart for demonstrating the flow of the abnormality diagnosis by a calculating part.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an abnormality diagnosis device for an internal combustion engine according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of an internal combustion engine (two-cycle diesel engine) provided with an abnormality diagnosis device for an internal combustion engine according to the present embodiment.

  First, the internal combustion engine 10 used in this embodiment will be described. FIG. 1 is a part of a power system constituting the internal combustion engine 10, and the internal combustion engine 10 according to the embodiment has a plurality of cylinders 14. The internal combustion engine is basically configured of an engine body 12 and a crankshaft 32 that transmits power generated by the engine body 12 to a drive system.

  The engine body 12 is configured based on a cylinder 14, a cylinder head 18, and a piston 26. On the inner surface of the cylinder 14, a sliding surface for sliding a piston 26, which will be described in detail later, is formed. Further, the inner surface of the cylinder 14 sealed by a cylinder head 18 to be described in detail later constitutes a combustion chamber 16 in which fuel (mixed gas) for generating power is burned. The cylinder 14 is provided with an air inlet 14 b for sending external air (hereinafter referred to as air supply) to the combustion chamber 16.

  The cylinder head 18 is a lid that covers the upper opening of the combustion chamber 16 in the cylinder 14 that is formed in a cylindrical shape. The cylinder head 18 is provided with a fuel injection valve 20 and an exhaust port 22. The fuel injection valve 20 plays a role of injecting fuel into the combustion chamber 16 at a timing when a piston 26, which will be described in detail later, reaches top dead center. The fuel sprayed in the compressed and heated gas burns as a mixed gas with the supply air, and pushes down the piston 26 by the expansion action of the gas to generate power. The fuel injection from the fuel injection valve 20 is continuously performed from the crank angle at which the piston 26 reaches several deg before and after the top dead center to the crank angle from about 15 to 20 deg after the top dead center. Is called.

  The exhaust port 22 is a passage for discharging the burned gas (exhaust gas) generated in the cylinder. An exhaust valve 24 is provided at the opening on the combustion chamber 16 side in the exhaust port 22. The exhaust valve 24 opens and closes at a predetermined timing and distributes the exhaust gas in the combustion chamber to the exhaust port.

  The piston 26 slides in a space constituting the combustion chamber 16 in the cylinder 14. The cross-sectional shapes of the piston 26 and the combustion chamber 16 are circular, and the diameter of the piston 26 is slightly smaller than the diameter of the combustion chamber 16. This is because, if the diameters of both are the same, loss of kinetic energy due to friction may increase or metal may bite. For this reason, a piston ring 28 is provided on the outer periphery of the piston 26. The outer shape of the piston ring 28 is formed larger than the diameter of the combustion chamber 16 in a free state, and the piston ring 28 is biased against the wall surface of the combustion chamber 16 in the combustion chamber 16. For this reason, the exhaust gas can be prevented from being blown from the side surface of the piston 26. In addition, as shown in FIG. 1, the piston ring 28 is provided with two or more (3-4 pieces) along the sliding direction.

  The crankshaft 32 is a crank-shaped shaft with which the rod 30 that transmits the power of the piston 26 is engaged, and plays a role of transmitting the power obtained by sliding of the piston 26 to the drive system. Sliding by the piston 26 is a reciprocating motion in the combustion chamber 16. By transmitting this to the crankshaft 32 via the piston rod 29, the cross head 31, and the rod 30, it can be converted into a rotational motion. The internal combustion engine 10 according to the embodiment is a so-called two-cycle engine that completes a cycle such as air supply, compression, combustion, and exhaust while the crankshaft 32 rotates once.

  The internal combustion engine 10 according to the embodiment includes a plurality of cylinders 14 as described above, and a crankshaft 32 connected to the piston 26 via a piston rod 29, a crosshead 31, and a rod 30 for each cylinder 14. The shift angle is different. With such a configuration, power can be efficiently obtained, and vibration (swing) caused by the movement of the piston 26 can be suppressed.

  Next, an abnormality diagnosis device for an internal combustion engine according to this embodiment (hereinafter simply referred to as an abnormality diagnosis device 40) will be described. The abnormality diagnosis device 40 according to the present embodiment includes an in-cylinder pressure sensor 42, a supply air temperature sensor 44, a supply air pressure sensor 46, a crank angle sensor 48, a calculation unit 50, and an output unit 56.

  The in-cylinder pressure sensor 42 is a sensor provided so that the pressure in the combustion chamber 16 can be detected. Specifically, it may be provided outside the pressure detection through-hole 14 a provided in the combustion chamber 16. With this configuration, the pressure in the combustion chamber 16 can be detected in real time.

The air supply temperature sensor 44 is a sensor provided in the air supply reservoir 34 to which the air supply air passage 36 connected to the air supply port 14 b provided for each cylinder 14 constituting the combustion chamber 16 converges. Thereby, the initial temperature of the gas supplied into the combustion chamber 16 can be detected in real time. By branching the air supply air passage 36 from the air supply reservoir 34, it is possible to supply a gas having a common temperature and a common pressure to each of the plurality of combustion chambers 16.
The air supply pressure sensor 46 is also a sensor provided in the air supply reservoir 34 and plays a role of detecting the initial pressure of the gas supplied into the combustion chamber 16 in real time.

  The crank angle sensor 48 is a sensor that detects the rotation angle of the crankshaft 32. The sensor for detecting the rotation angle of the crankshaft 32 may be a rotary encoder or the like. Of these various sensors, the in-cylinder pressure sensor 42 is provided for each cylinder 14 constituting the internal combustion engine 10. As for the crank angle sensor 48, for each cylinder 14, the top dead center, the bottom dead center, and the like are stored in the storage unit 52 of the calculation means 50 described later in detail.

  The calculation means 50 includes at least a storage unit 52 and a calculation unit 54. The storage unit 52 stores the specification data of the internal combustion engine 10 (engine) to be diagnosed, the physical property value of the combustion gas, and the various sensors described above (in-cylinder pressure sensor 42, supply air temperature sensor 44, supply air pressure sensor 46, crank It is responsible for storing data detected by the angle sensor 48). The data detected by the various sensors is stored in association with the angle data (θ) obtained by the crank angle sensor 48.

  The specification data of the internal combustion engine 10 may be, for example, the bore diameter of the combustion chamber 16, the stroke of the piston 26, and the minimum volume (top clearance volume) of the combustion chamber 16. This is because the volume of the combustion chamber 16 for each crank angle can be calculated with such data.

  Since the combustion gas is a mixed gas of air and fuel, the physical property value of air and the physical property value of fuel may be stored. As the physical property values of air, the density, gas constant, specific heat, etc. may be cited from a general physical property table. Further, the physical property value of the fuel may be a density, a lower heating value, a carbon / hydrogen ratio (C / H ratio), a specific heat, or the like, and may be measured in advance based on the fuel used.

Hereinafter, the function of the calculation unit 54 and the flow of abnormality diagnosis will be described with reference to FIG.
The calculation unit 54 plays a role of performing calculations for extracting various data stored in the storage unit 52 and performing abnormality diagnosis. In order to perform abnormality diagnosis, it is desirable to obtain a heat flux q (W / m ² ) between the combustion gas in the cylinder 14 and the wall surface of the combustion chamber 16. However, it is extremely difficult to obtain the heat flux q between the wall surfaces in the internal combustion engine being driven. For this reason, as an alternative value of the heat flux q based on actual measurement, an index ΣQ (θ) that relatively represents the magnitude of the heat flux q is obtained, and this index ΣQ (θ) is calculated in advance during normal operation. Determination based on the difference from the average value of the index (reference value ΣQ ₀ (θ): first reference value) may be performed. The normal operation means a state where an output corresponding to the rotational speed of the internal combustion engine 10 is obtained. In the case of a marine diesel engine, an output (kw) having a value proportional to the cube of the rotation speed (rpm) can be obtained.

で示すことができる。ただし、αは熱伝達率（Ｗ／ｍ^２・ｋ）、Ｔは燃焼室内ガス温度（ｋ）、Ｔｗａｌｌは燃焼室壁面表面温度（ｋ）である。なお、燃焼室壁面は、等熱流束壁であるものとする。また、Ｔｗａｌｌには実際上、高低の温度分布が存在し、実測することも困難である。このため、仮定値として、機関冷却水温度以上の予め定められた一定温度を与えることができる。ここで、熱伝達率α（Ｗ／ｍ^２・ｋ）は、

で示すように、ＰとＴを含む関数で推定することができる（数式２は、Ｅｉｃｈｅｌｂｅｒｇの式を用いた場合の例）。ただし、Ｃｍはピストン速度（ｍ／ｓ）、Ｐは燃焼室内圧力（ｋＰａ）である。上記気筒内圧力センサ４２では、燃焼室１６内の圧力をアナログデータ（電圧または電流等の変化）として得ることができる。このため、得られたアナログデータを、燃焼室内圧力値としてのデジタルデータに変換することで、燃焼室内圧力Ｐを得ることができる。一方、燃焼室内ガス温度Ｔは、理想気体の状態方程式である数式３を利用して求めることができる。

The heat flux q (W / m ² ) is

Can be shown. Where α is the heat transfer coefficient (W / m ² · k), T is the combustion chamber gas temperature (k), and Twall is the combustion chamber wall surface temperature (k). Note that the combustion chamber wall surface is an isothermal flux wall. In addition, there is actually a high and low temperature distribution in Twall, which is difficult to measure. For this reason, a predetermined constant temperature equal to or higher than the engine coolant temperature can be given as an assumed value. Here, the heat transfer coefficient α (W / m ² · k) is

As shown by, the function can be estimated by a function including P and T (Equation 2 is an example in the case of using the Eichenberg equation). However, Cm is a piston speed (m / s), P is a combustion chamber pressure (kPa). In the cylinder pressure sensor 42, the pressure in the combustion chamber 16 can be obtained as analog data (change in voltage or current). For this reason, the combustion chamber pressure P can be obtained by converting the obtained analog data into digital data as the pressure value in the combustion chamber. On the other hand, the combustion chamber gas temperature T can be obtained by using Equation 3 which is an ideal gas equation of state.

  That is, since the bore diameter of the combustion chamber 16, the stroke of the piston 26, and the top clearance volume are known, the volume V of the combustion chamber 16 can be obtained. Note that G is the total amount of the charged air and the combustion gas in the combustion chamber calculated based on the supply air temperature and the supply air pressure, and R is a gas constant (gas constant). Here, the total amount of combustion gas and the gas constant are values for a mixed gas of air and fuel.

と定めれば、数式１、２との関係において、

が成り立つ。ここで、定数Ｃについては、診断対象とする内燃機関毎に定まる一定の値である。このため、固有（診断対象とする）内燃機関の状態を相対的に診断する場合には、除することができる。よって、圧力値に基づいて定まる項（Ｐ）と、温度に基づいて定まる項（Ｔ）により構成される関数で表される値Ｑ（θ）について、熱流束の大きさを相対的に表す値とすることができる。 Thus, by calculating the combustion chamber gas temperature T using the ideal gas equation of state (Formula 3), the terms P and T in the heat transfer coefficient α shown in Formula 2 can be obtained. Then, based on the calculated combustion chamber pressure P and combustion chamber gas temperature T (P and T terms in the heat transfer coefficient α), a value Q (θ) relatively representing the magnitude of the heat flux can be obtained. it can. Here, for a value Q (θ) that relatively represents the size of the heat flux,

In the relationship with Equations 1 and 2,

Holds. Here, the constant C is a constant value determined for each internal combustion engine to be diagnosed. For this reason, it can be excluded when relatively diagnosing the state of the inherent (to be diagnosed) internal combustion engine. Therefore, a value that relatively represents the magnitude of the heat flux with respect to a value Q (θ) represented by a function composed of a term (P) determined based on the pressure value and a term (T) determined based on the temperature. It can be.

  Therefore, in the calculation unit 54, first, a cycle calculation for obtaining P and T is performed for each cylinder 14 unit (S110, S120), and based on this, a value Q (relatively representing the magnitude of the heat flux) θ) is obtained (S130).

と示すことができる。なお、ａは開始クランク角度（例えば１８０°）、ｂは終了クランク角度（例えば２２０°）をそれぞれ示す。このようにして算出可能とする、熱流束の大きさを相対的に示す指数ΣＱ（θ）は、実測値として得難い燃焼室壁面表面温度（Ｔｗａｌｌ）については、代替値として、予め定められた一定温度（機関冷却水温度以上の一定温度）と仮定することができる。よって、測定値から容易に求められるデータ（例えばＰ、Ｔ）に基づいて算出することができる。少なくとも、サイクル中において変化する、圧力値に基づいて定まる項（Ｐ）と、温度に基づいて定まる項（Ｔ）に基づいて指数ΣＱ（θ）を求めれば、異常事態の発生を算出数値の変動量として検出することが可能となるからである（Ｓ１４０）。 As described above, the calculation unit 54 that has calculated Q (θ) for each crank angle is an integrated value of Q (θ) between predetermined crank angles using the calculated Q (θ). Then, ΣQ (θ) is obtained as an index that relatively represents the size of the heat flux. The predetermined range of the crank angle is a predetermined angle from the time when fuel is injected into the combustion chamber until combustion occurs until the exhaust is exhausted. For example, in this embodiment, the crank angle is 180 ° (top dead center) to 220 °. The angle is up to. Where ΣQ (θ) is

Can be shown. Note that a represents a start crank angle (for example, 180 °), and b represents an end crank angle (for example, 220 °). The index ΣQ (θ) that relatively indicates the magnitude of the heat flux that can be calculated in this way is a predetermined constant as an alternative value for the combustion chamber wall surface temperature (Twall) that is difficult to obtain as an actual measurement value. It can be assumed that the temperature (a constant temperature higher than the engine coolant temperature). Therefore, it can be calculated based on data (for example, P, T) easily obtained from the measured value. If an index ΣQ (θ) is calculated based on at least a term (P) determined based on the pressure value and a term (T) determined based on the temperature, which changes during the cycle, the occurrence of an abnormal situation is calculated. This is because it can be detected as a quantity (S140).

Next, the computing unit 54 performs a first diagnosis (absolute value diagnosis). In the first diagnosis, first, a difference (first difference) between the exponent ΣQ (θ) obtained by the above calculation and the reference value ΣQ ₀ (θ) obtained in advance is obtained. After obtaining the difference, it is determined whether or not the difference exceeds a predetermined threshold (threshold in the first diagnosis). The determination is abnormal when the difference exceeds the threshold, and is normal when the difference is equal to or less than the threshold. When this is expressed by a mathematical formula, it is as shown in the mathematical formula 7.

By performing such a calculation, the diagnosis for each cylinder 14 is completed. Here, the threshold value in the first diagnosis may be about ± several% (for example, 5%) with the value of the reference value ΣQ ₀ (θ) as a base point, and can be determined by an empirical rule.

  By performing the absolute value diagnosis in units of the cylinders 14 as described above, it is possible to detect that there is an abnormal factor when the following abnormal state occurs. First, there is a case where the friction resistance of the hull increases due to dirt on the hull, and all the cylinders 14 are in a torque rich state. Specifically, the fuel injection amount is large for the rotation speed.

  Next, there is a case where the performance of the supercharger is lowered, the supply air pressure is lowered, or the amount of charged air is insufficient in all the cylinders 14. Specifically, the fuel mixing balance is lost and the temperature of the combustion gas is rising.

  Further, the cooling performance of the air is lowered, the supply air temperature is increased, or the charge air temperature is increased in all the cylinders 14 and the combustion gas temperature is increased due to this (S150). .

で求めれば良い。なお、ｎはシリンダ数（シリンダ単位に定められた番号）である。演算部５４は、平均指数を求めた後、平均指数とシリンダ毎の指数ΣＱ（θ）との差分（第２差分）を求める。差分を求めた後、当該差分が、予め定められた閾値（第２診断における閾値）を超えているか否かを判定する。判定は、差分が閾値を超えていた場合には異常、差分が閾値以下であった場合には、正常とされる。なお、閾値（第２診断における閾値）は、平均指数を基準として±数％（例えば５％）程度として定めれば良い。

このような演算を行うことにより、内燃機関全体における各シリンダの異常診断が終了する。 Next, the computing unit 54 performs a second diagnosis (variation diagnosis between each cylinder). In the second diagnosis, an average index ΣQ _A (θ) that is an average value of the indices ΣQ (θ) calculated in each of the plurality of cylinders 14 is obtained. The average index ΣQ _A (θ) is

Find it in Note that n is the number of cylinders (a number determined for each cylinder). After calculating the average index, the calculation unit 54 determines a difference (second difference) between the average index and the index ΣQ (θ) for each cylinder. After obtaining the difference, it is determined whether or not the difference exceeds a predetermined threshold (threshold in the second diagnosis). The determination is abnormal when the difference exceeds the threshold, and is normal when the difference is equal to or less than the threshold. The threshold value (threshold value in the second diagnosis) may be determined as about ± several% (for example, 5%) with reference to the average index.

By performing such calculation, the abnormality diagnosis of each cylinder in the entire internal combustion engine is completed.

  By performing such a diagnosis, it is possible to detect an abnormal state that could not be detected as an abnormal state in the absolute value diagnosis. Specifically, there are abnormalities caused by variations in the fuel injection amount due to poor adjustment, and variations in the fuel injection amount caused by fuel injection pumps or leakage outside the system. In addition, there is a variation in working gas temperature or combustion chamber pressure due to an exhaust valve malfunction or the like. In any state, in absolute value diagnosis, there is a possibility that it is within the reference value, and it may be possible to diagnose an abnormality for the first time when viewed as a variation of the whole internal combustion engine (S160).

  After completing each calculation, the result of diagnosis is output to the output means 56, and the calculation unit 54 repeats the above calculation again. This is because the abnormality may be caused by a time-series change. The output means 56 may be a display or the like, or may be a patrol lamp or an alarm device. This is because it is possible to determine whether the output means is abnormal or normal (S170).

  According to the abnormality diagnosing device 40 having such a configuration, the temperature of the constituent members in the internal combustion engine 10 is compared with the prior art in which the heat load is expressed by the exhaust gas temperature and output, and the pressure in the combustion chamber 16 (in-cylinder pressure). By quantitatively indicating the thermal load based on the index ΣQ (θ) that relatively represents the magnitude of the heat flux that determines the state of change, there are few errors due to repeated calculations. For this reason, the accuracy of the determination based on the comparison with the reference value is high, and the abnormality diagnosis can be performed with high accuracy. Also, by performing absolute value diagnosis for each cylinder and variation diagnosis between cylinders, it is possible to compensate for abnormal states that cannot be detected mutually, thereby improving the accuracy of abnormality diagnosis. be able to.

  In the above-described embodiment, the value Q that relatively represents the magnitude of the heat flux in a predetermined crank angle range is used as an index that represents the magnitude of the heat flux between the combustion gas in the cylinder 14 and the wall surface of the combustion chamber. It demonstrated using (SIGMA) Q ((theta)) which is an integrated value of ((theta)). However, the index employed in the calculation according to the embodiment may be any index that relatively represents the magnitude of the heat flux, and thus a value Q (relatively representing the magnitude of the heat flux in a predetermined crank angle range. Q (θ) av. which is an average value of θ). May be used as an index. This is because even when such a method is adopted, there is no problem in performing the abnormality diagnosis according to the present embodiment. In addition, Q (θ) av. In the case of using Q (θ) av. Needless to say, it is determined by following the above.

  In the above embodiment, the exponent ΣQ (θ) or the exponent Q (θ) av. As the predetermined range of the crank angle for obtaining the above, the predetermined angle from the time when the fuel is injected into the combustion chamber 16 to the exhaust after the combustion occurs is described. However, the exponent ΣQ (θ) and the exponent Q (θ) av. The crank angle range for obtaining the value may be an integrated value or an average value of Q (θ) during one cycle, that is, during one revolution of the crankshaft. By increasing the width of the crank angle range, Q (θ) in a portion that does not contribute to combustion is also calculated, but by performing a diagnosis with an index including data for one cycle, a compression process other than the combustion stroke It is possible to diagnose abnormalities in the entire cycle including the above.

  In the above embodiment, the exponents ΣQ (θ) and Q (θ) av. Are obtained using Q (θ) as a value representing the magnitude of the heat flux. I was looking for. In this case, it is described that Q (θ) is obtained by a function including a term (P) determined based on the pressure value and a term (T) determined based on the temperature. However, Q (θ) may be obtained by another alternative expression shown as a value relatively representing the magnitude of the heat flux. For example, the equation includes various parameters that allow the engine state such as cylinder diameter, average piston speed, and cylinder volume to be known. Since Q (θ) is not a value indicating the heat flux itself, but a value that substitutes for the heat flux (a value that relatively represents the magnitude of the heat flux), the parameter that constitutes the arithmetic expression representing this is also Can have a width.

DESCRIPTION OF SYMBOLS 10 ......... Internal combustion engine, 12 ......... Engine body, 14 ......... Cylinder, 14a ......... Pressure detection through hole, 14b ......... Air supply port, 16 ......... Combustion chamber, 18 ......... Cylinder Head, 20 ......... Fuel injection valve, 22 ......... Exhaust port, 24 ......... Exhaust valve, 26 ......... Piston, 28 ......... Piston ring, 29 ......... Piston rod, 30 ......... Rod, 31 ......... Crosshead, 32 ......... Crankshaft, 34 ......... Air supply reservoir, 36 ......... Air supply passage, 40 ......... Abnormality diagnosis device, 42 ......... In-cylinder pressure sensor, 44 ... ... Supply air temperature sensor, 46 ......... Supply air pressure sensor, 48 ......... Crank angle sensor, 50 ......... Calculation means, 52 ......... Storage section, 54 ......... Calculation section, 56 ......... Output means .

Claims (7)

An in-cylinder pressure sensor for detecting the pressure in the combustion chamber;
A crank angle sensor that detects the angle of the crankshaft that operates the piston;
A supply air temperature sensor for detecting a supply air temperature supplied into the combustion chamber;
An air supply pressure sensor for detecting the pressure of the air supply;
Computing means,
The calculation means includes: specification data in an internal combustion engine to be diagnosed, physical properties of combustion gas, pressure in the combustion chamber detected by the cylinder pressure sensor, crank angle detected by the crank angle sensor, and supply air temperature sensor. A storage unit that stores the detected supply air temperature and the supply air pressure detected by the supply air pressure sensor, and between the combustion gas in the combustion chamber and the combustion chamber wall surface based on the data stored in the storage unit Calculating an index relatively representing the magnitude of the heat flux of, and comparing the index and a reference value determined in advance to determine whether there is an abnormality in units of cylinders constituting the internal combustion engine; An abnormality diagnosis apparatus for an internal combustion engine, comprising: The calculation unit, after the first determination to determine whether there is an abnormality in the cylinder unit,
Comparing the index with an average index that is an average value of the indexes obtained for each cylinder at the time of the first determination, and performing a second determination for determining whether there is an abnormality in each cylinder constituting the internal combustion engine. The abnormality diagnosis device for an internal combustion engine according to claim 1, characterized in that:   3. The abnormality of the internal combustion engine according to claim 1, wherein the arithmetic unit obtains the index by a function including a term determined based on a pressure value and a term determined based on a temperature. Diagnostic device.   The function is an integrated value from a value relatively representing the heat flux at the crank angle at the combustion start timing in each cylinder to a value relatively representing the heat flux at the combustion end timing, or the crank The abnormality diagnosis device for an internal combustion engine according to claim 3, wherein the abnormality diagnosis device is a function for obtaining an integrated value of values relatively representing the magnitude of the heat flux during one rotation of the shaft.   The function is an average value from a value relatively representing the heat flux at the crank angle at the combustion start timing in each cylinder to a value relatively representing the heat flux at the combustion end timing, or the crank 4. The abnormality diagnosis device for an internal combustion engine according to claim 3, wherein the abnormality diagnosis device is a function for obtaining an average value of values relatively representing the magnitude of the heat flux during one rotation of the shaft.   In the first determination, the calculation unit obtains a difference between the exponent and a reference value obtained in advance, and the difference is normal when the difference is within a predetermined first threshold range. The abnormality diagnosis device for an internal combustion engine according to any one of claims 2 to 5, wherein the abnormality is determined when the engine is not within the first threshold range.   In the second determination, the calculation unit obtains a difference between the average index and the index obtained for each cylinder, and is normal when the difference is within a predetermined second threshold range, The abnormality diagnosis device for an internal combustion engine according to any one of claims 2 to 6, wherein the abnormality is determined when the difference is not within a range of a second threshold value.

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