JP2016118192A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exactly detect abnormality such as compression leakage, in a compression stroke of a cylinder of an internal combustion engine.SOLUTION: In a control device for an internal combustion engine, a polytropic index is calculated from the transition of fluctuations of in-cylinder pressure and an in-cylinder capacity in a compression stroke of a cylinder of an internal combustion engine. The calculated polytropic index is compared with a model value of the polytropic index estimated when the compression stroke is normally carried out, and on the basis of difference between them, the presence/absence of abnormality in the compression stroke of the cylinder is determined.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle or the like.

  In a compression stroke of a cylinder of an internal combustion engine, a “compression leakage” in which part of the intake air filled in the combustion chamber of the cylinder leaks out of the combustion chamber may occur (see, for example, the following patent document). In particular, recently, research and development has been progressing to further improve the fuel efficiency, aiming to further increase the compression ratio, and lowering the tension of the piston ring to reduce the friction between the cylinder bore and the piston. There is a tendency. Therefore, it can be said that the possibility of occurrence of compression leakage has increased.

JP 2014-080917 A

  An object of the present invention is to accurately detect an abnormality in a compression stroke of a cylinder of an internal combustion engine, typified by compression leakage.

  In order to solve the above-mentioned problems, in the present invention, a polytropic index is calculated from the transition of each variation in the cylinder pressure and the cylinder volume in the compression stroke of the cylinder of the internal combustion engine, and the calculated polytropic index is normally converted into the compression stroke. A control device for an internal combustion engine that compares the model value of the polytropic index that is assumed when the engine is operated and determines whether there is an abnormality in the compression stroke of the cylinder based on the difference between the two is configured. With such a configuration, it is possible to accurately detect a compression leak and other abnormalities that cause problems in the operation of the internal combustion engine.

  In addition, the type of abnormality can be estimated based on whether the calculated polytropic index is smaller or larger than the model value. If a severe compression leak that causes a problem in the operation of the internal combustion engine occurs, the calculated polytropic value falls below the model value of the polytropic index when normal. On the contrary, if the calculated polytropic value exceeds the model value, it can be determined that some abnormality other than the compression leakage has occurred in the compression stroke of the cylinder.

  Also, when the difference between the polytropic index calculated at a certain point in the compression stroke and the model value corresponding to that point is greater than the threshold, the polytropic index calculated at a point in the past or future than that point is compared with the model value. Then, it is possible to estimate the type of abnormality based on whether or not the difference between the two is less than the threshold value. If the polytropic index calculated for a time point in the past or in the future from the time point matches the model value corresponding to the time point, it is considered an abnormality related to the crank angle sensor signal indicating the time point in the compression stroke.

  According to the present invention, it is possible to accurately detect an abnormality in the compression stroke of a cylinder of an internal combustion engine, typified by compression leakage.

The figure which shows schematic structure of the internal combustion engine and control apparatus in one Embodiment of this invention. The figure which illustrates transition of the in-cylinder pressure in a compression stroke. The figure which illustrates each transition of the polytropic index calculated when the abnormal compression leakage has occurred in the compression stroke, and the model value of the polytropic index when the compression stroke is normally operated. The figure which illustrates each transition of the polytropic index calculated when the abnormality relevant to the crank angle sensor signal has occurred in the compression stroke, and the model value of the polytropic index when the compression stroke is operating normally. The figure which illustrates each transition of the polytropic index calculated when the abnormality relevant to the crank angle sensor signal has occurred in the compression stroke, and the model value of the polytropic index when the compression stroke is operating normally.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type four-stroke engine (gasoline engine), and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode. The ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  An external EGR (Exhaust Gas Recirculation) device 2 realizes a so-called high-pressure loop EGR. The EGR device 2 includes an external EGR passage 21 that communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21. And an EGR valve 23 that controls the flow rate of the EGR gas flowing through the EGR passage 21. The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface of the ECU 0 is output from a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle that is an output shaft of the internal combustion engine, and a crank angle sensor that detects the engine speed. A crank angle signal b, an accelerator pedal depression amount, or an opening degree of the throttle valve 32 is detected as an accelerator opening degree (ie, a required load), an accelerator opening degree signal c output from a sensor, and an intake passage 3 (in particular, a surge tank 33). ) The intake air temperature / intake pressure signal d output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure, the water temperature signal e output from the water temperature sensor for detecting the cooling water temperature indicating the temperature of the internal combustion engine, An outside air temperature signal f outputted from an outside air temperature sensor for detecting the air temperature, an atmospheric pressure signal g outputted from an atmospheric pressure sensor for detecting the atmospheric pressure, Cylinder pressure signal h or the like to be output from the cylinder pressure sensor for detecting the cylinder pressure cylinder 1 (the combustion chamber pressure) is input.

  The crank angle sensor senses the rotation angle of a rotor that is fixed to the shaft end of the crankshaft and rotates integrally with the crankshaft. The rotor is formed with teeth or protrusions at predetermined angles along the rotation direction of the crankshaft. Typically, each time the crankshaft rotates 10 °, teeth or protrusions are placed. The crank angle sensor faces the outer periphery of the rotor, detects that individual teeth or protrusions pass near the sensor, and transmits a pulse signal as a crank angle signal b each time. However, the crank angle sensor does not output 36 pulses during one revolution of the crankshaft. Some of the teeth or protrusions of the rotor of the crankshaft are missing. Each missing tooth portion corresponds to a specific rotational phase angle of the crankshaft. Due to the missing tooth portion, a part of the pulse train of the crank angle signal b is also lost. Based on this missing pulse, the absolute angle (posture) of the crankshaft, in other words, the current position of the piston of each cylinder 1 can be known.

  From the output interface of the ECU 0, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the throttle valve 32, and an opening operation for the EGR valve 23. The signal l and the like are output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed and the intake air amount, the required fuel injection amount, fuel injection timing (including the number of fuel injections for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR amount) ) Etc. are determined. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

  Further, the ECU 0 controls an electric motor (starter motor or ISG (Integrated Starter Generator), not shown) at the time of starting the internal combustion engine (a cold start or a return from an idling stop). The signal o is input, and cranking is performed to rotationally drive the crankshaft of the internal combustion engine by the electric motor. Cranking ends when the internal combustion engine starts from the first explosion to a continuous explosion and the engine speed, that is, the rotation speed of the crankshaft, exceeds a judgment value determined according to the coolant temperature, etc. (assuming that the explosion has been completed) To do.

  Thus, the ECU 0 of the present embodiment diagnoses whether each cylinder 1 of the internal combustion engine has an abnormality during the compression stroke.

  In order to accurately determine the presence or absence of an abnormality during the compression stroke, the ECU 0 determines whether the cylinder pressure (combustion chamber pressure) and the cylinder volume (combustion chamber volume) vary during the compression stroke of the target cylinder 1. A polytropic index related to a change in the state of intake air charged in the combustion chamber of the cylinder 1 is calculated. The in-cylinder pressure is the pressure of the intake air filled in the combustion chamber of the cylinder 1, and the in-cylinder volume is the volume of the intake air filled in the combustion chamber of the cylinder 1. Then, the calculated polytropic index is compared with a model value of the polytropic index assumed when the compression stroke is normally performed.

Changes in the pressure, density and temperature of the intake air by compressing the intake air (or mixture) in the combustion chamber of the cylinder 1 are regarded as a polytropic process. Then, if the cylinder pressure at the time point i in the compression stroke of the cylinder 1 is P _i and the cylinder volume at the same time point i is V _i , the change in the state of intake air from the time point (i−1) to the time point i The polytropic index n _i is
n _i = −log (P _i / P _i-1 ) / log (V _i / V _i-1 )
Is required. The subscript i represents the calculation opportunity of the polytropic index n _i , but the subscript i is replaced with the current crank angle (CA), that is, the rotation angle (posture) of the crankshaft, and the subscript (i−1) is replaced with the current crank angle. Alternatively, the crank angle may be replaced with a (past) crank angle that is back by a predetermined angle.

The in-cylinder pressure P _i can be obtained by referring to the in-cylinder pressure signal h provided from the in-cylinder pressure sensor. The in-cylinder volume V _i is geometrically determined from the current piston position of the target cylinder 1. The current piston position is determined by the current crank angle. The current crank angle can be obtained by referring to the crank angle signal b provided from the crank angle sensor. In the memory of the ECU 0, map data or a function expression that defines the relationship between the crank angle and the in-cylinder volume V _i of each cylinder 1 is stored in advance. The ECU searches the map using the current crank angle as a key or substitutes the current crank angle into the function formula to obtain the in-cylinder volume V _i of the target cylinder 1.

A typical abnormality in the compression stroke is a compression leak in which part of the intake air filled in the combustion chamber of the cylinder 1 leaks out of the combustion chamber. FIG. 2 shows the in-cylinder pressure during the compression stroke in a certain operation region [engine speed, accelerator opening (or intake pressure in the surge tank 33, intake air amount or fuel injection amount filled in the combustion chamber)]. It shows the transition of P _i. The horizontal axis is the crank angle, more specifically, the angle that goes back from the compression top dead center, and the right end thereof is BTDC 0 ° CA, that is, the compression top dead center. In FIG. 2, the broken line represents the transition of the in-cylinder pressure P _{i in} a normal case in which no compression leakage has occurred which causes a problem in the operation of the internal combustion engine. On the other hand, the solid line represents the transition of the cylinder pressure P _i when abnormal undergoing compression leakage such that operational problems of the internal combustion engine.

FIG. 3 shows the transition of the polytropic index n _i during the compression stroke under a certain operating region. 3, the broken line represents the transition of the polytropic exponent n _i of the normal case, the solid line represents the transition of the polytropic exponent n _i when undergoing abnormal compression leakage. The polytropic index n _i calculated when an abnormal compression leak occurs during the compression stroke is lower than the normal polytropic index n _i except for the vicinity of the compression top dead center, and does not exceed this.

If the calculated polytropic exponent n _i sometimes exceed the polytropic exponent n _i of the normal case, it is highly probable they are abnormal other than compressed leakage. 4 and 5 respectively show a case where the ECU 0 misidentifies the current crank angle, in other words, the position of the piston of each cylinder 1 due to a failure of the crank angle sensor or a failure in transmission / reception of the crank angle sensor signal b. The transition of the calculated polytropic index n _i is shown. The broken lines in FIGS. 4 and 5 are changes in the polytropic index n _{i in} the normal case, as in FIG. The solid line in FIG. 4, ECU0 a predetermined angle than the angle of rotation of the true crankshaft current crank angle is a transition of the polytropic exponent n _i when it knows (for example, 1 ° CA) advanced angle. And, the solid line in FIG. 5, ECU0 is transitive the polytropic exponent n _i when it knows the predetermined angle delayed angle than the angle of rotation of the true crankshaft current crank angle.

The misidentification of the crank angle by the ECU 0 affects the in _- cylinder volumes V _i and V _i−1 used for calculating the polytropic index n _i . If the ECU 0 misunderstands that the current crank angle is an angle advanced from the rotation angle of the true crankshaft, the values of the in-cylinder volumes V _i and V _{i-1 at} the calculation opportunity i are respectively actual (time points). i and the time (i-1)) of becomes smaller than the cylinder volume, an error is mixed into the polytropic exponent n _i as shown in FIG. This is calculated when, polytropic exponent n _i is expressed by the solid line, the compression stroke is assumed when Itonama normal, deviates the polytropic exponent n _i expressed by a broken line. In addition, the calculated polytropic index n _i exceeds or falls below the normal polytropic index n _i depending on the time during the compression stroke. According to the example shown in FIG. 4, in the period up to BTDC 60 ° CA Atari from BTDC100 ° CA Atari, polytropic exponent n _i calculated is below the polytropic exponent n _i of the normal case. On the other hand, the time to approach the subsequent compression top dead center, polytropic exponent n _i calculated tends to exceed the polytropic exponent n _i of the normal case.

On the other hand, if the ECU 0 mistakenly recognizes that the current crank angle is an angle delayed from the true crankshaft rotation angle, the in-cylinder volumes V _i and V _{i-1 at} the calculation opportunity i are respectively the actual cylinders. content becomes larger than the product, the error is mixed into the polytropic exponent n _i as shown in FIG. This is calculated when, polytropic exponent n _i is expressed by the solid line, the compression stroke is assumed when Itonama normal, deviates the polytropic exponent n _i expressed by a broken line. In addition, the calculated polytropic index n _i exceeds or falls below the normal polytropic index n _i depending on the time during the compression stroke. According to the example shown in FIG. 5, in a period of up to BTDC 60 ° CA Atari from BTDC100 ° CA Atari, polytropic exponent n _i being calculated exceeds the polytropic exponent n _i of the normal case. On the other hand, the time to approach the subsequent compression top dead center, polytropic exponent n _i calculated tends below the polytropic exponent n _i of the normal case.

As abnormalities other than those described above, it is possible that foreign matter exists in the combustion chamber of the cylinder 1 and the in-cylinder volumes V _i and V _i-1 are unduly reduced. The polytropic index n _i calculated in that case is higher than the normal polytropic index n _i except in the vicinity of the compression top dead center.

The normal polytropic index n _i under the condition that the temperature of the cylinder 1 of the internal combustion engine, the temperature and pressure of the intake air filled in the cylinder 1 are within the predetermined ranges, respectively, can be obtained experimentally by an actual machine test or the like. Is possible. In the memory of the ECU 0, the polytropic index n _i in the normal compression stroke when the cooling water temperature (or the lubricating oil temperature) of the internal combustion engine, the intake air temperature in the surge tank 33 and the intake air pressure are within predetermined ranges, respectively, is stored in advance. The model value _Ni is stored. This model value N _i is a time series that changes at each time point i, which is different at each time point i in the compression stroke.

In addition, during operation of the internal combustion engine, the ECU 0 performs a polytropic index in the compression stroke of the cylinder 1 when the cooling water temperature (or the lubricating oil temperature), the intake air temperature in the surge tank 33 and the intake pressure are within predetermined ranges. to calculate the n _i. Then, the calculated polytropic index n _i for each time point i is compared with the model value N _i for each time point i stored and held in the memory. Calculated polytropic exponent n _i and an absolute value of the difference between the model values N _i at the time i corresponding thereto | N _i -n _i | or both of the ratio N _i / n _i is over the entire compression stroke ( However, the time near the compression top dead center may be excluded.) If it is less than the threshold value, it is determined that the compression stroke of the cylinder 1 is normally performed.

Conversely, at any time point i in the compression stroke, the absolute value | N _i −n _i | of the difference between the calculated polytropic index n _i and the model value N _i or the ratio N _i / n _{i of the} both is equal to or greater than the threshold value. If it is enlarged, it is determined that some abnormality has occurred in the compression stroke of the cylinder 1.

Further, the ECU 0 can identify and specify the type of abnormality based on the magnitude relationship between the calculated polytropic index n _i and the model value N _i . That is, as shown in FIG. 3, when the calculated polytropic index n _i is equal to or less than the model value N _i for all the time points i (except the time near the compression top dead center) in the compression stroke, It is thought to be a compression leak. On the other hand, if the calculated polytropic index n _i is greater than or equal to the model value N _i for all time points i in the compression stroke (except for the time point near the compression top dead center), It is considered that a foreign object exists.

Alternatively, as shown in FIG. 4 or FIG. 5, when the calculated polytropic index n _i is mixed with a time when the calculated polytropic index n _i exceeds and falls below the model value N _i , the crank angle sensor signal It is considered that an abnormality related to b has occurred, and an error has occurred between the current crank angle recognized by the ECU 0 and the actual crank angle.

  The ECU 0 that has detected that an abnormality has occurred in the compression stroke of the cylinder 1 stores information (diagnosis code) indicating that fact in the memory. At this time, it is preferable to write information that can identify the type of the detected abnormality to help the investigation of the cause of the abnormality in the subsequent inspection and repair work.

  In addition, the fact that an abnormality has occurred in the compression stroke may be output in a manner that appeals to the driver's vision or hearing. For example, a warning light (engine check lamp) installed in a cockpit of a vehicle is turned on, displayed on a display, or a warning sound is output from a buzzer or a speaker.

In this embodiment, the polytropic index n _i is calculated from changes in the cylinder pressure P _i and the cylinder volume V _i during the compression stroke of the cylinder 1 of the internal combustion engine, and the calculated polytropic index n _i is normally compressed. Compared with the model value N _{i of the} polytropic index assumed when the stroke is operated, the abnormality in the compression stroke of the cylinder 1 is determined based on | N _i −n _i | or _Ni / n _i representing the difference between the two. The control device 0 for the internal combustion engine that determines the presence or absence is configured.

  According to the present embodiment, it is possible to accurately detect an abnormality in the compression stroke of the cylinder 1 of the internal combustion engine, represented by compression leakage. There is little concern that an abnormality in the compression stroke may be overlooked or that an abnormality has occurred even though no abnormality has occurred in the compression stroke.

In addition, according to the present embodiment, the type of abnormality can be estimated based on whether the calculated polytropic index n _i is smaller or larger than the model value N _i .

The present invention is not limited to the embodiment described in detail above. For example, assuming that there is an error α, that is, a time difference α between the current crank angle recognized by the ECU 0 and the actual crank angle, the true polytropic value n _i ′ at the time point i is
n _i ′ = −log (P _i− α / P _i-1- α) / log (V _i− α / V _i-1- α)
It is. Based on this fact, ECU0 it is determined that there is some abnormality in the compression stroke of the cylinder 1, than the time i for the past or future time point (i-alpha) recalculates the polytropic exponent n _i-alpha, A process of comparing the recalculated polytropic index n _i- α with the model value M _i corresponding to the time point i may be executed. Here, α may take a positive value or a negative value. | N _i −n _i- α | or N _i / n _{i -} α representing the difference between the polytropic index n _i- α recalculated by changing α and the model value M _i at the time point i is added to the entire compression stroke. If it falls below the threshold value (however, the time near the compression top dead center may be excluded), it becomes clear that the type of abnormality is a misrecognition of the current crank angle by ECU0.

On the other hand, if | N _i −n _i− α | or N _i / n _i− α expands beyond the threshold at any time point i in the compression stroke, other than misidentification of the current crank angle by ECU0. It can be determined that an abnormality has occurred in the compression stroke of the cylinder 1.

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be applied to control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder b ... Crank angle signal h ... In-cylinder pressure signal

Claims (3)

Calculate the polytropic index from the changes in the in-cylinder pressure and the in-cylinder volume during the compression stroke of the cylinder of the internal combustion engine, and the model value of the polytropic index that is assumed when the calculated polytropic index is normally operated And a control device for an internal combustion engine that determines whether there is an abnormality in the compression stroke of the cylinder based on the difference between the two. The control apparatus for an internal combustion engine according to claim 1, wherein the type of abnormality is estimated based on whether the calculated polytropic index is smaller or larger than the model value. When the difference between the polytropic index calculated for a certain point in the compression stroke and the model value corresponding to that point is greater than or equal to the threshold, the polytropic index calculated for a point in the past or future than that point is compared with the model value, The control apparatus for an internal combustion engine according to claim 1 or 2, wherein the type of abnormality is estimated based on whether or not the difference between the two is less than a threshold value.

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