JP4371168B2 - Abnormality diagnosis apparatus for in-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to an abnormality diagnosis apparatus for a direct injection internal combustion engine that determines an abnormality of a fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control.

  In an internal combustion engine, feedback control of the fuel injection amount, that is, air-fuel ratio feedback control is usually performed so that the actual air-fuel ratio matches the target air-fuel ratio, such as the theoretical air-fuel ratio. Here, for example, if any abnormality occurs in the fuel injection system, such as a fuel injection valve, it becomes difficult to supply a predetermined amount of fuel to the internal combustion engine. Therefore, the engine air-fuel ratio tends to greatly deviate from the target air-fuel ratio. As a result, the exhaust properties may be deteriorated. When such an abnormality occurs, the feedback correction amount for making the actual air-fuel ratio coincide with the target air-fuel ratio, that is, the air-fuel ratio correction amount becomes a very large value.

  Therefore, when executing the air-fuel ratio feedback control, the air-fuel ratio correction amount is monitored. When the air-fuel ratio correction amount increases excessively, it is determined that an abnormality has occurred in the fuel injection system. Is diagnosed (see, for example, Patent Document 1).

  By the way, the internal combustion engine is provided with a blow-by gas reduction device for processing gas leaking from the cylinder into the crankcase, so-called blow-by gas. Since blow-by gas is strongly acidic, it may cause rust on the metal part of the engine body or deteriorate the lubricating oil present in the body. This blow-by gas reducing device introduces fresh air into the engine body from the outside (more precisely, an air cleaner provided in the intake system), circulates it inside the crankcase, and finally returns to the intake system. By performing the processing, the blow-by gas is processed without being discharged to the outside.

The blow-by gas contains unburned fuel components. For this reason, if this is simply returned to the intake system, the fuel injection amount will be substantially changed. However, the concentration of the unburned fuel component contained in this blow-by gas is not so high and usually does not change greatly. For this reason, such fluctuations in the fuel injection amount can be dealt with in the air-fuel ratio feedback control as described above, and the adverse effects thereof can be suppressed to a level that can be ignored.
JP 2001-73853 A

  However, in a cylinder injection internal combustion engine in which fuel is directly injected into the cylinder from the fuel injection valve, unlike the intake port injection internal combustion engine, the injection hole of the fuel injection valve, the cylinder inner peripheral surface, Since the distance between the two is extremely short and the injected fuel can directly collide with the inner peripheral surface of the cylinder, the following problems cannot be ignored.

  That is, when the engine is cold, the atomization of fuel in the cylinder is difficult to promote, so that a part of the injected fuel remains attached to the cylinder inner circumferential surface (cylinder inner circumferential surface) without being used for combustion. It becomes the state of. The fuel adhering to the cylinder inner peripheral surface is mixed with the lubricating oil adhering to the cylinder inner peripheral surface for lubrication of the engine piston. As a result, dilution of the lubricating oil with the fuel, so-called fuel dilution occurs.

  The lubricating oil on the inner peripheral surface of the cylinder diluted with fuel is scraped off as the engine piston moves up and down and returned to the crankcase (more precisely, an oil pan formed as a part thereof). After that, it is again used for lubricating internal combustion engines such as engine pistons. Therefore, when such fuel dilution of the lubricating oil frequently occurs, the ratio of the fuel mixed in the lubricating oil in the crankcase, in other words, the entire lubricating oil used for lubricating the internal combustion engine gradually increases.

  When the ratio of the fuel contained in the lubricating oil increases in this way, a large amount of fuel evaporates from the lubricating oil, and the fuel concentration of the blow-by gas greatly increases. In particular, when the amount of fuel injection is relatively small, such as when the engine is under low load, when blow-by gas having a significantly increased fuel concentration is introduced into the intake system, the air-fuel ratio is attributed to this. The air-fuel ratio correction amount in the feedback control is excessively increased, and there is a possibility that a misdiagnosis indicating that there is an abnormality may be made despite no abnormality occurring in the fuel injection system.

  The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide a lubricating oil by fuel adhesion on the inner peripheral surface of a cylinder when diagnosing a fuel injection system abnormality based on an air-fuel ratio correction amount of air-fuel ratio feedback control. It is an object of the present invention to provide an abnormality diagnosis device for a direct injection internal combustion engine that can suppress as much as possible misdiagnosis caused by fuel dilution.

Hereinafter, means and effects for solving the above problems will be described.
According to a first aspect of the present invention, there is provided an in-cylinder provided with a determination means for determining abnormality of the fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control obtained based on a tendency of deviation between an actual air-fuel ratio and a target air-fuel ratio In the abnormality diagnosis device for an injection type internal combustion engine, an air-fuel ratio learning value is obtained for each of the engine load areas divided into a plurality of parts in order to compensate for a steady deviation tendency between the actual air-fuel ratio and the target air-fuel ratio. Restriction that restricts the determination operation that the determination means has an abnormality on the condition that the degree of deviation between the engine high load range value and the engine low load range value is large for each air-fuel ratio learning value obtained every time Means are provided.

  When the fuel evaporates from the lubricating oil, the rate of change of the fuel evaporation amount is extremely small as compared with, for example, the rate of change of the fuel injection amount accompanying a change in the engine operating state. Therefore, the correction amount for compensating the steady deviation tendency between the actual air-fuel ratio and the target air-fuel ratio, that is, the air-fuel ratio learning value reflects the deviation tendency of each air-fuel ratio due to the fuel evaporation amount. It becomes like this.

  Further, since the fuel injection amount from the fuel injection valve is relatively small at the time of engine low load, when the fuel evaporates from the lubricating oil, this fuel evaporation amount occupies the fuel amount supplied to the internal combustion engine. The ratio is larger than that during high engine load operation. Therefore, there is a difference in the deviation tendency between when the engine operating state is on the low load side and when it is on the high load side.

  In the invention described in claim 1, this point is taken into consideration, and on the condition that the difference between the engine high load range value and the engine low load range value is large for the air-fuel ratio learning value, A limitation is imposed on the determination operation for determining that there is an abnormality in the determination means. Therefore, it is possible to accurately determine that the amount of fuel evaporated from the lubricating oil is increasing, and to limit the determination operation that the determination means has an abnormality on the condition that this increases. As a result, the erroneous diagnosis caused by the fuel dilution of the lubricating oil can be suppressed as much as possible in the abnormality diagnosis of the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control.

  The divergence tendency is, for example, the difference between the engine high load range value KGH and the engine low load range value KGL (KGH-KGL) or the ratio (KGH / KGL) of the air-fuel ratio learning value. Can be requested. Even if the fuel is not evaporated from the lubricating oil, if there is a tendency of engine-specific divergence between the engine high load range value KGH and the engine low load range value KHL. It is also effective to make corrections to cancel the deviation tendency inherent in the engine with respect to the deviation and ratio.

  The invention according to claim 2 is the abnormality diagnosis apparatus for a direct injection internal combustion engine according to claim 1, wherein the limiting means has a large degree of deviation and the air-fuel ratio correction amount is an actual sky as the deviation tendency. The determination operation is limited on the condition that the fuel ratio is increased by a predetermined amount or more to compensate for the tendency to deviate to the rich side from the target air-fuel ratio.

  According to this configuration, in addition to the conditions concerning the degree of deviation, the amount of fuel evaporation due to fuel dilution increases as in the case of the invention according to claim 2, and the deviation of each air-fuel ratio actually occurs due to the increase. In this case, since the determination operation is restricted, it can be avoided that the determination operation is unnecessarily restricted.

  Further, the misdiagnosis related to the abnormality diagnosis of the fuel injection system becomes most prominent when the fuel injection amount from the fuel injection valve becomes relatively small. For this reason, according to a third aspect of the present invention, in the abnormality diagnosis device for a direct injection internal combustion engine according to the first or second aspect, the restriction is performed on the condition that the restriction means is at a low engine load. It is supposed to be added.

  According to this configuration, since the above-described limitation on abnormality determination is added on the condition that the engine is at low load, misdiagnosis can be suppressed as much as possible at such low engine load, while high engine load is high. In some cases, it is possible to avoid that the determination operation that is abnormal is unnecessarily limited.

  In addition, as a specific mode when the determination unit determines that there is an abnormality, a specific aspect is as follows. For example, as in the invention described in claim 4, the in-cylinder injection according to claims 1-3 The in-cylinder injection according to any one of claims 1 to 3, wherein, in the abnormality diagnosis device for an internal combustion engine, the limiting means prohibits the abnormality determination by the determination means, or according to the invention described in claim 5. In the abnormality diagnosis device for the internal combustion engine, a configuration in which the limiting means changes a condition for determining that the abnormality is present so that it is difficult to determine that the abnormality is present.

  According to the structure of Claim 4, it becomes possible to suppress a misdiagnosis more reliably. Further, according to the configuration of claim 5, by changing the condition for the determination means to determine that there is an abnormality, it is possible to avoid the above-described erroneous operation while avoiding excessively restricting the determination operation to be abnormal. Diagnosis can be suppressed.

  Further, as described above, when the degree of fuel dilution increases and the amount of fuel evaporated from the lubricating oil increases, the actual air-fuel ratio is greater than the target air-fuel ratio if there is no abnormality in the fuel injection system. There is a high possibility of showing a tendency to diverge toward the rich side. For this reason, even if an abnormality (rich abnormality) in which the actual air-fuel ratio greatly deviates to the rich side from the target air-fuel ratio occurs, is this caused by an abnormality in the fuel injection system that is the object of abnormality determination? It is difficult to determine whether or not the fuel evaporation from the lubricating oil is increasing.

  On the other hand, if there is an abnormality (lean abnormality) in which the actual air-fuel ratio deviates greatly from the target air-fuel ratio despite the increase in the amount of fuel evaporated from the lubricant, The fuel injection capability of the injection system has been reduced, and there is a high possibility that an abnormality that makes it difficult to supply a predetermined amount of fuel has occurred, and the possibility of erroneous diagnosis is rather low.

  In this respect, the invention according to claim 6 is the abnormality diagnosis device for the in-cylinder internal combustion engine according to any one of claims 1 to 5, wherein the limiting means deviates from the target air-fuel ratio to the rich side. It is assumed that the determination operation of the determination means that the rich abnormality is present is limited.

  According to this configuration, it is possible to suppress misdiagnosis as much as possible for the rich abnormality of the fuel injection system due to the fuel dilution of the lubricating oil, while quickly determining the lean abnormality that is difficult to be misdiagnosed. A diagnosis that there is an abnormality in the fuel injection system can be made.

  The temperature of the lubricating oil may be directly detected by an oil temperature sensor or the like, or may be obtained based on a parameter having a correlation with the lubricating oil temperature, such as an engine cooling water temperature. In addition, the initial value of the lubricating oil temperature is estimated based on the engine temperature at the time of starting the engine (for example, the engine cooling water temperature), and the total amount of heat of combustion after the engine is started (for example, the integrated value of intake air amount and fuel) The increase amount may be estimated based on the injection amount integrated value), and the current lubricating oil temperature may be determined based on the initial value and the increase amount.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described.
FIG. 1 shows a schematic configuration of an abnormality diagnosis apparatus according to the present embodiment, an internal combustion engine 10 to be diagnosed, a lubrication system 70 for supplying lubricating oil to the internal combustion engine 10, and the like.

As shown in FIG. 1, the internal combustion engine 10 is a cylinder injection type internal combustion engine that directly injects fuel from a fuel injection valve 20 into a combustion chamber 12 of each cylinder (cylinder) 17.
Inside each cylinder 17, an engine piston (hereinafter simply referred to as “piston”) 14 is provided so as to be able to reciprocate. A combustion chamber 12 is defined by a top surface of the piston 14 and a cylinder inner peripheral surface 18. Has been.

  An intake passage 11 and an exhaust passage 13 are connected to the combustion chamber 12. A throttle valve 26 is provided midway in the intake passage 11, and the intake air introduced into the combustion chamber 12 is metered by the throttle valve 26. The intake air introduced into the combustion chamber 12 when the intake valve 21 is opened is mixed with the fuel injected from the fuel injection valve 20 to become an air-fuel mixture. The air-fuel mixture is explosively burned by ignition of the spark plug 22 and then discharged from the combustion chamber 12 to the exhaust passage 13 when the exhaust valve 23 is opened. The exhaust passage 13 is provided with a catalyst device 27 having an exhaust purification function.

  The fuel injection valve 20 is connected to a delivery pipe 24, and fuel is supplied from the delivery pipe 24 with a predetermined pressure. The delivery pipe 24 is supplied with fuel of a predetermined pressure through a fuel pump (not shown). The fuel pressure in the delivery pipe 24, that is, the fuel injection pressure of the fuel injection valve 20 can be adjusted by appropriately changing the discharge amount of the fuel pump.

  Further, the lubrication system 70 of the internal combustion engine 10 includes an oil pan 74 formed as a part of the crankcase 19 and a lubricating oil supply device 72. The lubricating oil supply device 72 includes an oil pump, a filter, an oil jet mechanism (all not shown), and the like. The lubricating oil in the oil pan 74 is sucked by the oil pump through the filter and supplied to the oil jet mechanism. In order to lubricate between the piston 14 and the cylinder inner peripheral surface 18, the lubricating oil thus supplied to the oil jet mechanism is supplied from the mechanism to the cylinder inner peripheral surface 18. Thereafter, as the piston 14 reciprocates, the lubricating oil is scraped downward from the cylinder inner circumferential surface 18 and finally returned to the oil pan 74.

  Then, the scraped lubricating oil is mixed with the lubricating oil in the oil pan 74 and then used for lubricating the internal combustion engine 1 again. The lubricating oil supplied to the cylinder inner peripheral surface 18 and used for lubricating the piston 14 rises in temperature due to engine combustion heat and is then returned to the oil pan 74. Therefore, when the circulation of the lubricating oil by the lubricating system 70 is started as the engine is started, the average temperature of the entire lubricating oil gradually increases until the lubricating oil shifts to a thermal equilibrium state. become.

  Further, the internal combustion engine 10 is provided with a blow-by gas reduction device 80 for scavenging blow-by gas existing inside the crank case 19 and processing it. The blow-by gas reduction device 80 includes a communication passage 82 that communicates a portion upstream of the throttle valve 26 and the inside of the head cover 16 in the intake passage 11, and a portion downstream of the throttle valve 26 and the head cover 16 in the intake passage 11. A blow-by gas passage 84 communicating with the inside is provided.

  When intake negative pressure is generated in the intake passage 11 as the internal combustion engine 10 is operated, fresh air is introduced into the head cover 16 through the communication passage 82. The fresh air is mixed with the blow-by gas, circulated inside the internal combustion engine 10, and finally discharged to the intake passage 11 through the blow-by gas passage 84. The blow-by gas is processed through the scavenging process of the blow-by gas reduction device 80 without being discharged to the outside. A flow rate adjusting valve 86 for adjusting the flow rate of the blowby gas in the blowby gas passage 84 is provided in the middle of the blowby gas passage 84.

  The combustion mode of the internal combustion engine 10 is controlled according to the engine load state. For example, during high load operation, the combustion mode is set to homogeneous combustion. During this homogeneous combustion, the fuel injection amount and the like are controlled so that the air-fuel ratio A / F is close to the theoretical air-fuel ratio (for example, “A / F = 12 to 15”), and the fuel injection timing is during the intake stroke. (Intake stroke injection).

  On the other hand, during low load operation, the combustion mode is set to stratified combustion. In this stratified combustion, the fuel injection amount and the like are controlled so that the air-fuel ratio A / F is leaner than the stoichiometric air-fuel ratio (for example, “A / F = 17 to 40”), and the fuel injection timing is the compression stroke. It is set in the latter period (compression stroke injection).

  Further, during the medium load operation, the combustion mode is set to weak stratified combustion in order to smoothly switch the combustion mode between stratified combustion and homogeneous combustion while suppressing fluctuations in engine output and the like. In this weakly stratified combustion, combustion is performed with a weaker stratification degree than during stratified combustion. During weak stratified combustion, the fuel injection amount and the like are controlled so that the air-fuel ratio A / F is leaner than the stoichiometric air-fuel ratio (for example, “A / F = 15 to 25”). Performed in both compression strokes (two-stage injection).

  Note that when the engine is cold (for example, the period during which the engine coolant temperature THW is equal to or lower than the predetermined temperature THWL), the atomization of the injected fuel tends to be difficult to promote. For this reason, when the engine is cold, the combustion mode is set to homogeneous combustion and the intake stroke injection is executed regardless of the engine load state. As a result, compared with the stratified combustion in which the compression stroke injection is performed, a longer period from fuel injection to ignition is ensured, and atomization of the injected fuel is promoted as much as possible.

  Further, after the engine is warmed up (for example, after the engine cooling water temperature THW has become equal to or higher than the predetermined temperature THWL), the learning of the air-fuel ratio learning value has been completed during the current engine operation even during the low load operation. When a predetermined condition is satisfied such as when there is no engine, the combustion mode is set to homogeneous combustion regardless of the engine load state.

  The control relating to the combustion mode is performed by the electronic control unit 50. The electronic control unit 50 performs overall control of the internal combustion engine 10 such as air-fuel ratio control and fuel injection control. In addition to a calculation device, a drive circuit, and the like, calculation results of various controls and their calculation A memory 52 for storing a function map and the like used in is provided.

  Further, the internal combustion engine 10 is provided with various sensors for detecting the operation state. For example, an intake air amount sensor 42 that detects an intake air amount is provided upstream of the throttle valve 26 in the intake passage 11. A rotation speed sensor 43 that detects the rotation speed (engine rotation speed) is provided in the vicinity of the output shaft (not shown) of the internal combustion engine 10. An accelerator sensor 44 that detects the amount of depression (accelerator opening) is provided in the vicinity of the accelerator pedal 60. A water temperature sensor 45 for detecting the temperature of the engine cooling water is attached to the cylinder block (not shown). Further, an oxygen sensor 46 for detecting an air-fuel ratio based on the oxygen concentration of the exhaust is attached upstream of the catalyst device 27 in the exhaust passage 13. The detection results of these sensors 42 to 46 are taken into the electronic control unit 50. The electronic control unit 50 executes various controls according to the engine operating state based on these detection results.

  Next, among these various controls, a control procedure for calculating the fuel injection amount at the time of homogeneous combustion (fuel injection amount calculation processing, air-fuel ratio feedback control, air-fuel ratio learning processing), fuel injection valve 20 and delivery pipe 24, or this A control procedure (abnormality determination process, prohibition condition determination process) for diagnosing such an abnormality of the fuel injection system of the internal combustion engine 10 such as a fuel pump for supplying fuel to the engine will be described.

  Note that when the engine is cold, a part of the fuel injected from the fuel injection valve 20 into the combustion chamber 12 adheres to the cylinder inner peripheral surface 18, and this fuel adhesion causes fuel dilution in the entire lubricating oil, resulting in fuel evaporation. As described above, when the amount increases, there is a possibility that an erroneous diagnosis is eventually caused in the abnormality diagnosis of the fuel injection system.

  Therefore, in the abnormality diagnosis control of the fuel injection system according to the present embodiment, a history that the internal combustion engine 10 has been operated under a condition where the degree of fuel dilution increases, specifically, a history that a cold short trip has been made is monitored. Through this process (operation history monitoring process), it is monitored that such fuel dilution of the entire lubricating oil has occurred, and this is actually having an adverse effect on the air-fuel ratio feedback control. In such a situation, by prohibiting the abnormality diagnosis control, it is avoided as much as possible that an erroneous diagnosis indicating that the fuel injection system is abnormal is made.

[1. Operation history monitoring process]
First, the driving history monitoring process will be described.
The flowcharts of FIGS. 2 and 3 show the procedure of the operation history monitoring process. The electronic control unit 50 repeatedly executes a series of processes shown in these drawings with a predetermined time period T. Further, the timing chart of FIG. 4 shows an example of the control mode based on this process.

  In this series of processing, it is determined whether or not the operation of the internal combustion engine 10 has been stopped (step S100 in FIG. 2). Incidentally, even after the operation of the internal combustion engine 10 is stopped, electric power is continuously supplied to the electronic control device 50 until the predetermined period elapses, and the electronic control device 50 is in a state in which the operation is possible. The electronic control unit 50 performs post-processing necessary for the next engine operation, such as storing and holding the execution results of various controls during the engine operation in the memory 52 before the predetermined period after the engine stops. To do.

  When it is determined that the engine has been stopped (step S100: YES, timings t2, t4, and t6 in FIG. 4), the value of the engine cooling water temperature THW at the time of starting the engine (hereinafter referred to as “the engine starting water temperature THWST”). Is read from the memory 52, and it is determined whether or not the temperature is equal to or lower than a predetermined temperature THWL (step S110). Here, the combustion is terminated without being subjected to combustion with a part of the injected fuel adhering to the cylinder inner peripheral surface 18, that is, the engine is started under the situation where there is a concern about the fuel dilution as described above. Judgment is made whether or not.

  Here, when it is determined that the engine start water temperature THWST is equal to or lower than the predetermined temperature THWL (step S110: YES), that is, when the current engine start is performed under a situation where there is a concern about the occurrence of fuel dilution. (Timing t1, t3, t5, t7 in FIG. 4), it is further determined whether or not the intake air amount integrated value GASUM after the engine start is equal to or less than a predetermined amount GASUM (step S120).

  Even when the engine starting water temperature THWST is low, if the internal combustion engine 10 is continuously operated over a long period of time, the temperature of the combustion chamber 12 rises and atomization of the injected fuel is promoted. Therefore, the fuel adhesion on the cylinder inner peripheral surface 18 is also suppressed accordingly. Further, the temperature of the lubricating oil gradually rises due to the engine combustion heat, and the amount of fuel evaporated from the lubricating oil increases with the rise.

  Therefore, even if the engine starting water temperature THWST is low and the fuel dilution level temporarily increases in the early stage of engine operation, the fuel dilution level gradually increases due to the evaporation of fuel from the lubricating oil during the subsequent engine operation. It will decrease. Then, if the increase in the fuel dilution degree generated in the initial stage of the engine operation is canceled or exceeded through the decrease in the fuel dilution degree, the internal combustion engine 10 is under a situation where the fuel dilution degree is increased. There is no need to leave a history of driving, that is, a cold short trip.

  Here, the amount of combustion heat generated by each combustion explosion has a correlation with the amount of intake air at that time and the fuel injection amount set based on the amount of intake air, and the amount of combustion heat tends to increase as these increase. is there. For this reason, it is considered that the amount of combustion heat generated during the engine operation period has a correlation with the integrated value GSUM of the intake air amount.

  Therefore, by appropriately setting the predetermined amount GSUML in step S120, the temperature of the lubricating oil rises during operation of the engine and the fuel evaporates, thereby reducing the degree of fuel dilution generated in the initial stage of engine operation through a decrease in the degree of fuel dilution. It is possible to appropriately determine that the increase in the amount is offset or exceeded.

  Note that step S120 is always negatively determined after the time point at which execution of stratified combustion is permitted as the engine coolant temperature rises. That is, in this step S120, the combustion mode is set to homogeneous combustion when the engine is cold, and the intake air amount integrated value during the period in which the intake stroke injection is executed becomes a substantial comparison object with the predetermined amount GSUMML. ing.

  In step S120, when it is determined that the intake air amount integrated value GASUM is equal to or less than the predetermined amount GSUML (step S120: YES), it is determined that the current engine operation corresponds to a cold short trip. In this case, the dilution degree counter value C is counted up by a predetermined amount a (step S130, timings t2, t4, and t6 in FIG. 4). This dilution degree counter value C indicates the degree of progress of dilution of the entire lubricating oil by the fuel, and becomes larger as the fuel dilution degree increases, and becomes smaller as the fuel dilution degree decreases. As shown in FIG. The count-up process in step S130 is executed only once after the engine is stopped, under the condition that the process has not yet been performed after the engine stop is determined.

  When the dilution degree counter value C is incremented in this way, it is next determined whether or not the dilution degree counter value C is equal to or greater than the determination value CH (step S140). Here, when the dilution degree counter value C is equal to or larger than the determination value CH (step S140: YES), the fuel dilution degree of the entire lubricating oil is increased, and when the fuel dilution further proceeds, the air-fuel ratio feedback control is performed. As a result, it is determined that there is a possibility of adverse effects on the abnormality determination process executed based on the air-fuel ratio correction amount in the same control. Then, on the condition that such a determination is made, the fuel dilution occurrence flag XS is set to “ON” (step S150, timing t4 in FIG. 4). In the prohibition condition determination process described later, the fact that the fuel dilution occurrence flag XS is set to “ON” is one of the conditions for prohibiting the determination that there is an abnormality. . When the operation of the fuel dilution occurrence flag XS is performed in this way, this series of processing is once ended.

  On the other hand, when it is determined in the previous step S100 that the internal combustion engine 10 is in operation (step S100: NO), it is next determined whether or not the engine coolant temperature THW is equal to or higher than a predetermined temperature THWH. (Step S160 in FIG. 3).

  Here, by comparing the engine coolant temperature THW with the predetermined temperature THWH, it is determined whether or not the average temperature of the entire lubricating oil has risen to a predetermined temperature or higher. Finally, as the temperature rises, the lubricating oil It is determined whether or not the amount of fuel evaporated from the whole has risen to a predetermined amount and the degree of fuel dilution is reduced. That is, if the engine coolant temperature THW is increased, it can be considered that the amount of combustion heat generated after the engine is started is large. For this reason, it can be easily determined that the temperature of the entire lubricating oil has risen due to the heat of combustion, and the amount of fuel evaporation has increased to such an extent that the degree of fuel dilution has been reduced.

  Here, when it is determined that the engine coolant temperature THW is equal to or higher than the predetermined temperature THWH, in other words, the fuel evaporation amount increases to a predetermined amount or more as the temperature of the entire lubricating oil increases (step S160: YES), the dilution degree counter value C is counted down by a predetermined amount b (step S170, timings t8 and t9 in FIG. 4). The countdown process in step S170 is executed on the condition that a predetermined time has elapsed since the process was performed last time. That is, the dilution degree counter value C is counted down every time a predetermined time elapses after the engine coolant temperature THW becomes equal to or higher than the predetermined temperature THWH.

On the other hand, when it is determined that the engine coolant temperature THW is lower than the predetermined temperature THWH (step S170: NO), this countdown process is not executed.
Next, it is determined whether or not the dilution degree counter value C is equal to or smaller than a determination value CL (<determination value CH) (step S180). Here, when the dilution degree counter value C is equal to or less than the determination value CL (step S180: YES), the fuel dilution degree of the entire lubricating oil is small, and accordingly, fuel dilution is temporarily generated by fuel injection and the lubricating oil. Even if the overall fuel dilution degree has progressed, it is determined that the adverse effect on the abnormality determination process is almost negligible.

  Then, on the condition that such a determination is made, the fuel dilution occurrence flag XS is set to “OFF” (step S190, timing t9 in FIG. 4). Then, after the fuel dilution occurrence flag XS is turned off in this way, this series of processing is once ended.

  On the other hand, when the dilution degree counter value C is equal to or larger than the determination value CL (step S180: NO), the operation of the fuel dilution occurrence flag XS is not performed, and this series of processes is temporarily ended.

  On the other hand, when it is determined in each of steps S110 and S120 in FIG. 2 that the engine starting water temperature THWST exceeds the predetermined temperature THWL (step S110: NO), or when the intake air amount integrated value after engine startup is determined. When it is determined that the GSUM exceeds the predetermined amount GSUMML (step S120: NO), it is determined that the current engine operation does not correspond to the cold short trip. In these cases, the series of processing is temporarily terminated without performing the count-up processing of the dilution degree counter value C.

  If it is determined in step S140 that the dilution degree counter value C is less than the determination value CH (step S140: NO), since the current engine operation corresponds to a cold short trip, the dilution degree counter value Although C is counted up, it is determined that the adverse effect on the abnormality determination process due to the degree of fuel dilution has not yet been reached to the extent that it cannot be ignored. In this case, the series of processes is temporarily terminated without turning on the fuel dilution occurrence flag XS.

[2. Fuel injection amount calculation process]
Next, the fuel injection amount calculation process will be described.
FIG. 5 is a flowchart showing a control procedure for calculating the fuel injection amount. A series of processing shown in this flowchart is repeatedly executed by the electronic control unit 50 with a predetermined period.

  In this series of processing, first, parameters indicating the current engine operating state such as the intake air amount, the engine rotational speed, the engine cooling water temperature THW, etc. are read (step S200). Based on these parameters, the basic fuel injection amount QBASE is calculated (step S210).

Next, the final fuel injection amount QINJ is calculated based on the following arithmetic expression (step S230).

QINJ
← QBASE {1+ (FAF−1.0) + (KGi−1.0)} K1 + K2 (1)
(K1, K2: correction coefficient)

In the above equation (1), “FAF” is a feedback correction coefficient for compensating for a temporary deviation tendency of the actual air-fuel ratio with respect to the theoretical air-fuel ratio that is the target air-fuel ratio. On the other hand, “KGi” is an air-fuel ratio learning value for compensating for a steady deviation tendency of the actual air-fuel ratio with respect to the theoretical air-fuel ratio. The air-fuel ratio learning value KGi is obtained as a value corresponding to each of the plurality of divided engine load regions. Specifically, the engine load area is divided into five areas Ri (i = 1 to 5) based on the magnitude of the intake air amount.

  Here, the region R1 is the region on the lowest load side, and the region R5 is the region on the lowest load side. The subscript “i” of the air-fuel ratio learning value KGi indicates a correspondence relationship with this region Ri. That is, when calculating the fuel injection amount shown in the above equation (1), if the engine load region is in the region R3, for example, the air-fuel ratio learning value KG3 corresponding to the engine load region is selected.

  The air-fuel ratio learning value KGi is obtained through air-fuel ratio feedback processing and air-fuel ratio learning processing described later. At this time, if the degree of fuel dilution increases and the actual air-fuel ratio tends to deviate from the stoichiometric air-fuel ratio due to an increase in the amount of fuel evaporation from the lubricating oil, this tendency is the air-fuel ratio learned value KGi. It will be reflected in.

When the final fuel injection amount QINJ is calculated in this way, this series of processing is once ended.
[3. Air-fuel ratio feedback processing]
Next, the air-fuel ratio feedback process will be described with reference to FIGS.

  FIG. 7 is a flowchart showing the calculation procedure of the feedback correction coefficient FAF, and a series of processes shown in the flowchart are repeatedly executed by the electronic control unit 50 with a predetermined period.

In this series of processing, first, it is determined whether or not a condition for performing the air-fuel ratio feedback processing is satisfied (step S300). Here, as an execution condition of this air-fuel ratio feedback processing, for example,
(Condition 1) Not at engine start (Condition 2) Fuel cut not performed (Condition 3) Engine cooling water temperature THW is equal to or higher than a predetermined temperature (Condition 4) Activation processing of oxygen sensor 46 is completed be able to.

  When at least one of these conditions 1 to 4 is not satisfied, it is determined that the execution condition for the air-fuel ratio feedback processing is not satisfied (step S300: NO). In this case, the feedback correction coefficient FAF is set to “1.0” (step S340), and this series of processes is temporarily terminated. Therefore, in this case, feedback control of the fuel injection amount based on the feedback correction coefficient FAF is not substantially performed.

  On the other hand, when all of the above conditions 1 to 4 are satisfied and execution of the air-fuel ratio feedback process is permitted (step S300: YES), whether or not the output voltage Vox of the oxygen sensor 46 is smaller than a predetermined reference voltage Vr. Is determined (step S302).

  If the output voltage Vox is less than the reference voltage Vr (step S302: YES), the air-fuel ratio identification flag XOX is set to “0”, assuming that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio (step S310). ).

  Next, the value of the air-fuel ratio identification flag XOX is compared with the value XOXO in the previous control period of the air-fuel ratio identification flag XOX (hereinafter simply referred to as “previous value XOXO”) (step S312). If they match (step S312: YES), it is determined that the state where the air-fuel ratio is on the lean side of the stoichiometric air-fuel ratio continues. In this case, a predetermined integral amount a (a> 0) is added to the feedback correction coefficient FAF, and the added value (= FAF + a) is set as a new feedback correction coefficient FAF (step S314).

  On the other hand, when the value of the air-fuel ratio identification flag XOX is different from the previous value XOXO (step S312: NO), the air-fuel ratio is inverted from the rich side value to the lean side value with respect to the theoretical air-fuel ratio. Judged to be. In this case, a predetermined skip amount A (A> 0) is added to the feedback correction coefficient FAF, and the added value (= FAF + A) is set as a new feedback correction coefficient FAF (step S316). The skip amount A is set to a sufficiently large value as compared with the previous integration amount a.

  On the other hand, when the output voltage Vox of the oxygen sensor 46 is equal to or higher than the reference voltage Vr (step S302: NO), the air-fuel ratio identification flag XOX is set to “1” assuming that the air-fuel ratio is richer than the stoichiometric air-fuel ratio. It is set (step S320).

  Next, the value of the air-fuel ratio identification flag XOX is compared with the previous value XOXO (step S322). If they match (step S322: YES), it is determined that the state where the air-fuel ratio is on the richer side than the stoichiometric air-fuel ratio continues. In this case, a predetermined integration amount b (b> 0) is subtracted from the feedback correction coefficient FAF, and the subtraction value (= FAF−b) is set as a new feedback correction coefficient FAF (step S324). .

  On the other hand, when the value of the air-fuel ratio identification flag XOX is different from the previous value XOXO (step S322: NO), the air-fuel ratio is inverted from the lean side value to the rich side value based on the theoretical air-fuel ratio. Judged to be. In this case, a predetermined skip amount B (B> 0) is subtracted from the feedback correction coefficient FAF, and the subtraction value (= FAF−B) is set as a new feedback correction coefficient FAF (step S326). . The skip amount B is set to a sufficiently large value as compared with the previous integral amount b.

  Then, after executing the process of step S326 or the previous step S316, the air-fuel ratio learning process, that is, the calculation of the air-fuel ratio learned value KGi is performed (step S330). Thereafter, in preparation for the next process, the current air-fuel ratio identification flag XOX is stored as the previous value XOXO (step S332), and this series of processes is temporarily terminated.

  FIG. 6 shows a transition example of the feedback correction coefficient FAF calculated through such air-fuel ratio feedback processing. As shown in FIG. 6, when the output voltage Vox of the oxygen sensor 46 changes across the reference voltage Vr (skip timing), the feedback correction coefficient FAF is set so as to change relatively large. A period from when the output voltage Vox of the oxygen sensor 46 changes over the reference voltage Vr to when it changes over the reference voltage Vr again (integration period) while being increased or decreased based on the amounts A and B Then, the increase / decrease operation is performed based on the integration amounts a and b so as to change relatively gradually.

  Here, when the actual air-fuel ratio and the stoichiometric air-fuel ratio do not have a tendency to steadily deviate, the feedback correction coefficient FAF varies around the reference value “1.0”. It becomes like this. Therefore, the average value FAFAV of the feedback correction coefficient FAF is substantially equal to “1.0”. On the other hand, if the actual air-fuel ratio tends to steadily deviate from the stoichiometric air-fuel ratio to the rich side or the lean side due to, for example, a solid difference in injection characteristics in the fuel injection valve 20 or fuel evaporation from the lubricating oil, feedback is performed. The correction coefficient FAF varies around the value different from the reference value “1.0”. Therefore, the average value FAFAV of the feedback correction coefficient FAF converges to a value different from “1.0” according to the deviation tendency. Therefore, the steady deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio is monitored based on the deviation between the reference value (= “1.0”) of the feedback correction coefficient FAF and the average value FAFAV. Can do. In the process according to the previous step S330, the air-fuel ratio learning value KGi is calculated as a parameter for monitoring this steady deviation tendency.

[4. Air-fuel ratio learning process]
Next, the air-fuel ratio learning process will be described with reference to the flowchart of FIG. A series of processing shown in this flowchart is repeatedly executed by the electronic control device 50 with a predetermined period.

  In this series of processes, first, it is determined whether or not the execution condition of the air-fuel ratio learning process is satisfied (step S3302). An example of the execution condition is that the internal combustion engine 10 is in a completely warmed-up state. If the execution condition for the air-fuel ratio learning process is not satisfied (step S3302: NO), this series of processes is temporarily terminated.

  On the other hand, when the execution condition of the air-fuel ratio learning process is satisfied (step S3302: YES), the average value FAFAV of the feedback correction coefficient FAF is calculated according to the following arithmetic expression (2) (step S3304).

FAFAV ← (FAFB + FAF) / 2 (2)

In the above equation, “FAFB” is the value of the feedback correction coefficient FAF when the previous skip processing, that is, the increase / decrease operation based on the skip amounts A and B is performed. That is, here, the feedback correction coefficient FAF value FAFB when the output voltage Vox of the oxygen sensor 46 changes across the reference voltage Vr, and then the output voltage Vox of the oxygen sensor 46 again crosses the reference voltage Vr. An arithmetic average with the value of the feedback correction coefficient FAF when changed is calculated as the average value FAFAV.

  After the average value FAFAV of the feedback correction coefficient FAF is calculated in this way, the current feedback correction coefficient FAF is stored as the value FAFB at the previous execution of the skip process in preparation for the next calculation process (step S3306).

  Next, the average value FAFAV of the feedback correction coefficient FAF is compared with predetermined values α, β (β> 1.0> α) (steps S3308, S3310). When the average value FAFAV of the feedback correction coefficient FAF is less than the predetermined value α (step S3308: YES), it is determined that the actual air-fuel ratio tends to deviate to the rich side from the theoretical air-fuel ratio. The air-fuel ratio learning value KGi is learned to be a smaller value to compensate for the deviation tendency. That is, the predetermined value γ is subtracted from the current air-fuel ratio learned value KGi, and the subtracted value (KG−γ) is set as a new air-fuel ratio learned value KGi (step S3314).

  On the other hand, when the average value FAFAV of the feedback correction coefficient FAF is equal to or larger than the predetermined value β (step S3310: NO), it is determined that the actual air-fuel ratio tends to deviate from the theoretical air-fuel ratio toward the lean side. The air-fuel ratio learning value KGi is learned to be a larger value to compensate for the deviation tendency. That is, the predetermined value γ is added to the current air-fuel ratio learned value KGi, and the added value (KG + γ) is set as a new air-fuel ratio learned value KGi (step S3312). After the air-fuel ratio learning value KGi is updated in this step S3312 or the previous step S3314, this series of processing is once ended.

  On the other hand, when the average value FAFAV of the feedback correction coefficient FAF is greater than or equal to the predetermined value α and less than the predetermined value β, the average value FAFAV fluctuates in the vicinity of the reference value “1.0”. Therefore, it is determined that the actual air-fuel ratio does not tend to deviate from the stoichiometric air-fuel ratio. In this case, the series of processes is temporarily terminated without updating the air-fuel ratio learned value KGi.

[5. Abnormality judgment processing]
Next, the abnormality determination process will be described with reference to the flowchart of FIG. A series of processing shown in this flowchart is repeatedly executed by the electronic control device 50 with a predetermined period.

  In this series of processing, first, the air-fuel ratio correction amount FAFKGi is calculated based on the following arithmetic expression (3) (step S500). The subscript “i” indicates a correspondence relationship with each engine load region Ri, as with the air-fuel ratio learning value KGi.

FAFKGi ← FAF + KGi-2 (3)

The air-fuel ratio correction amount FAFKGi includes a feedback correction coefficient FAF that changes according to a temporary deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio, and an air-fuel ratio that changes according to a steady deviation tendency between these air-fuel ratios. The overall behavior with the learning value KGi is shown. In other words, it is a parameter that comprehensively evaluates the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio. Specifically, this air-fuel ratio correction amount FAFKGi is, for example, when the actual air-fuel ratio tends to deviate more than the stoichiometric air-fuel ratio as a deviation tendency between the actual air-fuel ratio and the stoichiometric air-fuel ratio. Becomes a negative value (air-fuel ratio correction amount FAFKGi <0). On the other hand, if the actual air-fuel ratio tends to deviate from the stoichiometric air-fuel ratio as a deviation tendency between the actual air-fuel ratio and the stoichiometric air-fuel ratio, that is, shows a lean tendency, a positive value (air-fuel ratio correction amount FAFKGi> 0). Therefore, when the actual air-fuel ratio and the theoretical air-fuel ratio coincide with each other, that is, when there is no difference between the air-fuel ratios, the reference value is “0”.

  In calculating the air-fuel ratio correction amount FAFKGi, since the air-fuel ratio learning value KGi is referred to, the actual air-fuel ratio and the stoichiometric air-fuel ratio are caused by fuel injection system abnormality or fuel evaporation from the lubricating oil due to fuel dilution. If there is a steady divergence tendency, the air-fuel ratio correction amount FAFKGi changes according to the divergence tendency.

  Note that, in calculating the air-fuel ratio correction amount FAFKGi, the feedback correction coefficient FAF is also referred to in addition to the air-fuel ratio learning value KGi for the following reason. That is, since the accuracy of the air-fuel ratio learning value KGi decreases when the conditions for executing the air-fuel ratio learning process execution condition are small, it is considered as a parameter for comprehensively evaluating the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio. In this case, the reliability of the air-fuel ratio correction amount FAFKGi may be reduced. For this reason, when the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio changes, the feedback correction coefficient FAF that can change relatively quickly in response to the change is also referred to when calculating the air-fuel ratio correction amount FAFKGi. I am doing so.

  When the air-fuel ratio correction amount FAFKGi is calculated in this way, it is next determined whether or not a condition for determining that the fuel injection system is abnormal (abnormality determination condition) is satisfied (steps S510 and S520).

Here, when any one of the following conditions (1) and (2) is satisfied, it is determined that the abnormality determination condition is satisfied.
(1) The predetermined time has passed with the air-fuel ratio correction amount FAFKGi being equal to or greater than the determination value JMAX2 (> 0) (lean abnormality).

(2) The predetermined time has elapsed with the air-fuel ratio correction amount FAFKGi being equal to or less than the determination value JMIN2 (<0) (rich abnormality).
Here, whether or not the predetermined time has passed is determined by a counter value that is counted up every predetermined time from the time when the air-fuel ratio correction amount FAFKGi becomes equal to or greater than the determination value JMAX2 or when the determination value JMIN2 or less. The determination is based on the fact that the duration counter value Cj) exceeds the predetermined value Cj1 (Cj> Cj1).

  If it is determined that the abnormality determination condition is satisfied (steps S510 and S520: YES), it is determined that an abnormality has occurred in the fuel injection system (step S530). Then, this series of processes is temporarily terminated.

  On the other hand, when the air-fuel ratio correction amount FAFKGi is within the abnormality determination region RJ [JMIN2 <FAFKGi <JMAX2] (step S510: NO), it is not determined that there is an abnormality in the current process, and the duration counter value After Cj is reset to “0” (S540), this series of processing is temporarily terminated.

  Further, when the air-fuel ratio correction amount FAFKGi is out of the abnormality determination region RJ, but the duration counter value Cj is less than the predetermined value Cj1 (step S520: NO), this series of processes is temporarily ended. The That is, in this case, although the air-fuel ratio correction amount FAFKGi shows a tendency to increase, this may be due to temporary fluctuations, and since this reliability is still low, an abnormality occurs. The decision that it is being held is put on hold.

[6. Prohibition condition judgment process]
Next, the prohibition condition determination process will be described with reference to the flowchart of FIG. A series of processing shown in this flowchart is repeatedly executed by the electronic control device 50 with a predetermined period.

  In this series of processing, first, it is determined whether or not a deviation between the actual air-fuel ratio and the theoretical air-fuel ratio due to fuel dilution actually occurs (step S600). More specifically, here, the degree of fuel dilution is large and the air-fuel ratio correction amount FAFKGi has increased by a predetermined amount or more to compensate for the rich tendency as a deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio. It is determined whether or not. Specifically, when both of the following conditions (1) and (2) are satisfied, it is determined that the situation is present.

(1) The fuel dilution flag XS is set to “ON”.
(2) The air-fuel ratio correction amount FAFKGi is equal to or smaller than the determination value JMIN1 (where JMIN2 <JMIN1 <0).

  Here, the condition (2) is that the air-fuel ratio correction amount FAFKGi is increased by a predetermined amount (JMIN1) or more to compensate the rich tendency as a deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio. This is a condition for judging.

  When it is determined that the above situation is present (step S600: YES), whether or not the internal combustion engine 10 is next operated in the engine low load range, specifically, the engine load range, It is determined whether or not the region Ri is located on the lowest load side among the regions Ri divided based on the magnitude of the intake air amount (step S610).

  If it is determined that the internal combustion engine 10 is operating in the engine low load range (step S610: YES), it is prohibited to determine that the fuel injection system is abnormal. Specifically, the previous duration counter value Cj is reset to “0” (step S620). That is, here, the duration counter value Cj is reset to “0” so as to be always determined to be negative in step S520 shown in FIG. Like to do.

  Incidentally, by executing such prohibition processing, when the degree of fuel dilution is large (the fuel dilution occurrence flag XS is “ON”), it is substantially prohibited to determine that the rich abnormality is present. It will be. That is, when the fuel dilution occurrence flag XS is set to “ON”, the previous [5. This is because even if the condition (2) of rich abnormality in the abnormality determination process] is satisfied, the condition (2) (FAFKGi ≦ JMIN1) is always satisfied, so that the abnormality is not determined in the end. . In this way, after the determination that there is an abnormality is prohibited, this series of processing is temporarily terminated.

Similarly, when a negative determination is made in the previous steps S620 and S610, this series of processing is once ended.
According to the apparatus according to this embodiment configured to diagnose an abnormality related to the fuel injection system with the aspect described above, the following operational effects can be obtained.

  (1) The degree of fuel dilution of the whole lubricating oil used for lubricating the internal combustion engine 10 is estimated based on the dilution degree counter value C, and the estimated fuel dilution degree of the whole lubricating oil is large (the occurrence of fuel dilution). Flag XS = “ON”), and therefore, the execution condition is that the amount of fuel evaporation from the lubricating oil is increasing, and a restriction is imposed on the determination that there is an abnormality in the fuel injection system. Banned.

Accordingly, it is possible to reliably suppress misdiagnosis due to the fuel dilution of the lubricating oil in the abnormality diagnosis.
(2) In particular, when performing such a prohibition, the execution condition is that not only the degree of fuel dilution is large, but also that the air-fuel ratio correction amount FAFKGi is increased by a predetermined amount or more to compensate for the rich tendency. . Therefore, when the fuel evaporation amount due to fuel dilution increases and the air-fuel ratio deviation actually occurs due to the increase, the determination that there is an abnormality is prohibited. Therefore, for example, when the air-fuel ratio correction amount FAFKGi compensates for the lean tendency, in other words, if there is no risk of misdiagnosis due to a large degree of fuel dilution, the above prohibition is not made.

Therefore, it can be avoided that the determination that there is an abnormality is prohibited unnecessarily.
(3) The history of the operation of the internal combustion engine 10, that is, the history of the cold short trip, is monitored under the condition where the fuel dilution degree increases, and the monitoring result is used when the dilution degree counter value C is operated. I try to refer to it. Accordingly, it becomes possible to estimate the degree of fuel dilution of the entire lubricating oil, which is generally difficult to detect directly, relatively easily.

  (4) Further, when the engine is stopped, such a cold short circuit is provided on the condition that the water temperature THWST at the time of starting the engine is equal to or lower than the predetermined temperature THWL and the integrated intake air amount GASUM after the engine is started is equal to or lower than the predetermined amount GSUMML. It is determined that a trip has been made. Therefore, the determination can be made accurate, and the reliability of the history of the operation of the internal combustion engine 10 under the situation where the degree of fuel dilution increases can be improved.

  (5) Further, when such a cold short trip is performed, the dilution degree counter value C is counted up, and whether or not the fuel dilution degree is reduced through comparison between the engine cooling water temperature THW and the predetermined temperature THWL. And the countdown is performed so that the dilution degree counter value C gradually decreases when the fuel dilution degree is in a state of decreasing. Therefore, whether the fuel dilution degree of the entire lubricating oil increases or decreases, this can be accurately estimated based on the dilution degree counter value C, and based on the dilution degree counter value C. The determination that there is an abnormality can be appropriately prohibited.

[Second Embodiment]
Next, a second embodiment of the present invention will be described.
In the present embodiment, the calculation procedure for the degree of fuel dilution of the entire lubricating oil is different from that in the first embodiment.

  That is, in this embodiment, the increase rate and the decrease rate of the fuel dilution degree of the entire lubricating oil are periodically calculated, and the currently estimated value of the fuel dilution degree is based on the calculated increase rate and decrease rate. And the updated value is learned as a new value of the fuel dilution degree.

Hereinafter, the calculation process of the fuel dilution degree by the apparatus of this embodiment will be described focusing on the differences from the first embodiment.
FIG. 11 is a flowchart showing a processing procedure of this fuel dilution degree calculation processing. The electronic control unit 50 repeatedly executes a series of processes shown in FIG. 11 with a predetermined time period T.

  In this series of processing, first, the fuel dilution amount ΔFD per unit time based on the following arithmetic expression (4), that is, the fuel newly mixed into the lubricating oil through the fuel injection performed during the time period T described above. Is calculated (step S700). The fuel dilution amount ΔFD corresponds to the increase rate of the fuel dilution degree when the fuel evaporation from the entire lubricating oil is not taken into consideration.

ΔFD ← Σf (QINJi, AINJi, THWi) (4)
i = 1, 2, 3,..., n

Here, f () is a function for obtaining the fuel dilution amount generated by one fuel injection, and the fuel injection amount QINJ, the fuel injection timing AINJ, and the engine cooling water temperature THW when the fuel injection is executed. Is the parameter. “I” indicates how many times the fuel injection corresponds to the previous control cycle.

For example, when the fuel injection is performed three times from the previous control cycle to the current control cycle, the calculation formula (4) can be expressed as the following formula (5).

ΔFD
← f (QINJ1, AINJ2, THW1) + f (QINJ2, AINJ2, THW2) + f (QINJ3, AINJ2, THW3) (5)

The function f () is obtained in advance through experiments or the like, and is stored as a function map in the memory 52 of the electronic control unit 50. The basic characteristics are as follows.

The value of the function f () increases as the fuel injection amount QINJ increases. The value of the function f () increases as the fuel injection timing AINJ is retarded. The function f () decreases as the engine coolant temperature THW decreases. The value of increases
The reason why the fuel injection amount QINJ, the fuel injection timing AINJ, and the engine coolant temperature THW are selected as the parameters of the function f () is as follows.

  That is, the fuel dilution caused by the fuel injection occurs when the fuel adhering to the cylinder inner peripheral surface 18 remains without being combusted. Therefore, as the amount of fuel adhering to the cylinder inner peripheral surface 18 increases, the lubrication increases. It is thought that the fuel dilution degree of the whole oil will also increase greatly. It is usually difficult to directly detect the amount of fuel adhering to the cylinder inner peripheral surface 18, but if a parameter having a correlation with the amount of fuel adhering is appropriately selected, this can be obtained by accurately estimating it. become able to.

The fuel injection amount QINJ, the fuel injection timing AINJ, and the engine coolant temperature THW are all representative examples of parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18.
For example, if the fuel injection amount QINJ increases, the amount of fuel attached to the cylinder inner peripheral surface 18 naturally increases.

  Further, when the fuel adheres to the cylinder inner peripheral surface 18, there is an upper limit for the amount of fuel that can adhere per unit area, in other words, the thickness of the fuel layer formed on the cylinder inner peripheral surface 18. . Therefore, if the fuel adhesion area increases, the thickness of the fuel layer will not reach the upper limit value, and more fuel can adhere to the cylinder inner peripheral surface 18. Then, this fuel adhesion area, that is, the area of the cylinder inner peripheral surface 18 exposed to the combustion chamber 12 without being covered by the piston 14 at the time of fuel injection is determined by the fuel injection timing AINJ, and assuming the intake stroke injection, The fuel injection timing AINJ increases as the retard timing is set. Accordingly, the fuel adhesion amount on the cylinder inner peripheral surface 18 increases as the fuel injection timing AINJ is set to a more retarded timing.

  Further, the fuel adhesion on the cylinder inner peripheral surface 18 or the like basically becomes noticeable when the atomization of the injected fuel is not promoted and its particle size is large. In addition, the degree of atomization greatly depends on the temperature of the combustion chamber 12 and the fuel when the fuel injection pressure is constant. Further, the temperatures of the combustion chamber 12 and the fuel have a correlation with the engine cooling water temperature THW. Therefore, as the engine coolant temperature THW is lower, the atomization of the fuel is not promoted, so that the amount of fuel adhering to the cylinder inner peripheral surface 18 increases.

  In the apparatus according to the present embodiment, in consideration of these points, the fuel injection amount QINJ, the fuel injection timing AINJ, and the engine coolant temperature THW are selected as parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18. I have to.

  Once the fuel dilution amount ΔFD is calculated in this way, the fuel evaporation amount per unit time ΔFV, that is, evaporation from the entire lubricating oil during the time period T, based on the following equation (6): The amount of fuel to be calculated is calculated (step S710). Further, this fuel evaporation amount ΔFV corresponds to the rate of decrease in the degree of fuel dilution when fuel dilution by fuel injection is not taken into consideration.

ΔFV ← g (THWST, QINJSUM) (6)

Here, g () is a function for obtaining the fuel evaporation amount ΔFV per time period T, and uses the engine start water temperature THWST and the fuel injection amount integrated value QINJSUM after the engine start as parameters. Incidentally, the engine starting water temperature THWST is used for estimating the initial temperature of the lubricating oil at the time of starting the engine, and the fuel injection amount integrated value QINJSUM after the engine starting is used to estimate the subsequent increase in the temperature of the lubricating oil. Is for. That is, the function g () is basically for estimating the lubricating oil temperature and converting the estimation result into the fuel evaporation amount. This function g () is obtained in advance through experiments or the like, and is stored as a function map in the memory 52 of the electronic control unit 50. The basic characteristics are as follows.

・ The value of g () increases as the engine coolant temperature THWST increases. ・ The value of g () increases as the fuel injection amount integrated value QINJSUM after the engine starts increases.
When the fuel dilution amount ΔFD and the fuel evaporation amount ΔFV per unit time are calculated in this way, the fuel dilution degree FDSUM is calculated based on the following equation (7) (step S720).

FDSUM ← FDSUM + ΔFD−ΔFV (7)

As shown in the calculation formula (7), the current fuel dilution degree FDSUM is updated based on the increase rate ΔFD and the decrease rate ΔFV of the fuel dilution degree FDSUM. The updated value is learned as a new fuel dilution degree FDSUM and stored in the memory 52 of the electronic control unit 50.

  Next, the fuel dilution degree FDSUM and the determination value FDSUMH are compared (step S730). Here, when the fuel dilution degree FDSUM is equal to or greater than the determination value FDSUMH (step S730: YES), the fuel dilution degree of the entire lubricating oil is increased, and when the fuel dilution further proceeds, the adverse effect is no longer ignored. It is determined that it will become so large that it cannot be done. Then, on the condition that such a determination is made, the fuel dilution occurrence flag XS is set to “ON” (step S740).

  On the other hand, when the fuel dilution degree FDSUM is less than the determination value FDSUMH (step S730: NO), the fuel dilution degree FDSUM and the determination value FDSUML (<FDSUMH) are compared (step S735). Here, when the fuel dilution degree FDSUM is equal to or less than the determination value FDSUML (step S735: YES), the fuel dilution degree of the entire lubricating oil is small, and accordingly, fuel dilution is temporarily generated by fuel injection and the entire lubricating oil is lost. Even if the degree of fuel dilution progresses, it is determined that the adverse effect on the internal combustion engine 10 due to this is almost negligible. Then, on the condition that such a determination is made, the fuel dilution occurrence flag XS is set to “OFF” (step S745).

  After the fuel dilution occurrence flag XS is operated in steps S740 and S745, or when both of the previous steps S730 and S735 are negative, this series of processes is temporarily terminated.

  Then, in the previous prohibition condition determination process (see FIG. 10), the determination relating to the condition (1) of step S600 is made using the fuel dilution occurrence flag XS operated through this fuel dilution degree calculation process. This is the same as the apparatus according to the first embodiment.

  According to the apparatus according to the present embodiment that diagnoses the abnormality relating to the fuel injection system with the aspect described above, in addition to those described in the first embodiment (1) and (2), The following effects can be obtained.

  (6) An increase rate (fuel dilution amount per unit time) ΔFD of the fuel dilution degree FDSUM is calculated for each predetermined time period T based on a parameter having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18. Yes. Then, the current fuel dilution degree FDSUM is updated based on the calculated increase speed ΔFD, and this is learned as a new fuel dilution degree FDSUM. Therefore, this can be accurately and accurately estimated as the fuel dilution degree FDSUM increases, and the effects described in (1) and (2) can be achieved more effectively. It becomes like this.

  (7) Further, in such learning, not only the increase rate (fuel dilution amount per unit time) ΔFD of the fuel dilution degree FDSUM but also the decrease rate (fuel evaporation amount per unit time) ΔFV is determined by the engine. It is calculated based on the lubricating oil temperature estimated from the starting water temperature THWST and the fuel injection amount integrated value QINJSUM after starting the engine. Based on both the increase rate ΔFD and the decrease rate ΔFV, the fuel dilution degree FDSUM is updated and learned. Therefore, it becomes possible to estimate this more accurately by combining both the increase and decrease of the fuel dilution degree FDSUM.

  (8) Further, as parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18, those having a stronger correlation with the fuel adhesion amount, such as the fuel injection amount, the fuel injection timing, and the engine temperature are selected. Therefore, the fuel dilution degree FDSUM can be estimated more accurately.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
In the present embodiment, in step S600 of the previous prohibition condition determination process (FIG. 10), it is determined whether or not a deviation between the actual air-fuel ratio and the theoretical air-fuel ratio due to fuel dilution actually occurs. The determination method is different from that of the first embodiment.

  In other words, in the first embodiment, the history of the operation of the internal combustion engine 10 under the situation where the degree of fuel dilution increases, that is, the history of the cold short trip is monitored, and the fuel dilution is performed based on the monitoring result. It was estimated that the degree was large. On the other hand, in the present embodiment, when the degree of deviation between the engine high load range value and the engine low load range value is large for the air-fuel ratio learning value KGi, it is estimated that the degree of fuel dilution is large. Yes.

Specifically, the condition (1) in the process of step S600 shown in FIG. 10 is changed as follows.

(1) | KG5-KG1 |> JKG

Here, as described above, “KG5” is the air-fuel ratio learned value KGi in the region R5 on the highest load side, and “KG1” is the air-fuel ratio learned value KGi in the region R1 on the lowest load side. “JKG” is a determination value for determining that the degree of deviation between the air-fuel ratio learning values KG1 and KG5 in these engine load regions is large.

  When the fuel evaporates from the lubricating oil, the rate of change of the fuel evaporation amount is extremely small, and the steady divergence tendency between the actual air-fuel ratio and the target air-fuel ratio is reflected in the air-fuel ratio learning value KGi. .

  Further, when the engine is under a low load, the fuel injection amount from the fuel injection valve 20 is relatively small. Therefore, when the fuel evaporates from the lubricating oil, this fuel evaporation accounts for the amount of fuel supplied to the internal combustion engine 10. The ratio of quantity becomes large compared with the engine high load operation. Therefore, the air-fuel ratio learning value KG1 at the time of engine low load is easily affected by the amount of evaporated fuel, and a difference in the tendency of deviation is seen as compared with the air-fuel ratio learning value KG5 at the time of engine high load operation.

  For this reason, the condition (1) is used to monitor the degree of divergence between the air-fuel ratio learning values KG1 and KG5, so that an abnormal condition can be obtained after accurately determining that the amount of fuel evaporation from the lubricating oil has increased. It is possible to prohibit the determination of being present.

As a result, also in this embodiment, it is possible to obtain the same operational effects as (1) and (2) described in the first embodiment.
The apparatus according to each embodiment described above can be implemented by changing a part of the configuration and the control procedure as follows.

  In each embodiment, the fact that the air-fuel ratio correction amount FAFKGi is equal to or less than the determination value JMIN1 is included in the condition for prohibiting the determination that there is an abnormality. Only the fact that XS is set to “ON” or that the difference between the air-fuel ratio learning values KG1 and KG5 in the engine load region is large (| KG5-KG1 |> JKG) is set as such a prohibition condition. It may be.

  In each of the above embodiments, the determination that there is an abnormality is prohibited, but instead of performing such a prohibition, for example, in step S510 of FIG. 9, the determination value JMIN2 is set to a smaller negative value. The condition for determining an abnormality may be changed so that it is difficult to make such a determination, such as changing to a value or increasing the predetermined value Cj1 in step S520.

  -In the third embodiment, the degree of deviation between the value of the engine high load range and the value of the engine low load range is evaluated based on these differences. it can. Alternatively, for example, the air-fuel ratio learning value of the low load region R1 is estimated by extrapolation based on the air-fuel ratio learning values KG5 to KG3 of the load regions R3 to R5 on the high load side, and the estimated value and the actual air-fuel ratio learning are estimated. The degree of deviation may be evaluated based on a comparison with the value KG1.

  In the first embodiment, in the process of step S160 in FIG. 3, the engine cooling water temperature THW is compared with the predetermined temperature THWH to evaporate from the entire lubricating oil as the average temperature of the entire lubricating oil increases. It was determined that the amount of fuel to be increased to a predetermined amount. Here, in order to obtain the fuel evaporation amount more accurately, for example, the following method may be used. That is, the initial value of the lubricating oil temperature is estimated based on the engine starting water temperature THWST, and then the fuel injection amount integrated value after the engine is started (if the homogeneous combustion is selected as the combustion mode, this is taken in) The temperature rise amount is estimated based on the air amount integrated value). The fuel evaporation amount can also be obtained based on the lubricating oil temperature obtained as an addition value of the initial value and the temperature increase amount.

  In the first embodiment, when the engine starting water temperature THWST is equal to or lower than the predetermined temperature THWL and the intake air amount integrated value GASUM after the engine is started is equal to or lower than the predetermined amount GSUMML, the engine operation this time is a cold short trip. Judgment conditions when judging that it falls under. For example, the engine operating time from when the engine is started until it is stopped is counted, and the engine starting water temperature THWST is equal to or lower than a predetermined temperature THWL and the engine operating time is equal to or lower than a predetermined value. The above determination may be made based on this.

  -In 1st Embodiment, you may make it variably set predetermined amount GASUML compared with the intake air amount integrated value GASUM after an engine start according to engine starting water temperature THWST. Specifically, it is desirable to set this so that the predetermined amount GSUML decreases as the engine starting water temperature THWST increases.

  In the first embodiment, the dilution degree counter value C is incremented by a predetermined amount α. Here, as the degree of deviation between the engine start water temperature THWST and the predetermined temperature THWL (eg, the deviation (THWL-THWST), etc.) increases, the fuel dilution amount tends to increase. It is also effective to increase the degree as the degree increases. Similarly, the degree of divergence between the intake air amount integrated value GASUM after the engine start and the predetermined amount GSUMML (for example, the difference (GASUML−GASUM)) is increased so that the predetermined amount α increases as the divergence degree increases. It may be. Furthermore, a configuration in which the predetermined amount α is variably set based on both of these degrees of deviation is also effective.

  In the first embodiment, the dilution degree counter value C is counted down by a predetermined amount β. Here, as the degree of divergence between the engine coolant temperature THW and the predetermined temperature THWH (for example, the deviation (THW−THWH), etc.) increases, the amount of fuel evaporation tends to increase. You may make it increase, so that is large.

  In the first embodiment and the above-described modification, when determining whether the current engine operation corresponds to a cold short trip, the intake air amount integrated value GASUM after the engine start and the place corresponding thereto The fixed amount GSUML is compared, but instead of the intake air amount integrated value GASUM after starting the engine, the fuel injection integrated value after starting the engine can be adopted.

  In the above embodiments, when calculating the air-fuel ratio correction amount FAFKGi, both the feedback correction coefficient FAF and the air-fuel ratio learning value KGi are referred to as shown in the above equation (3). Only the learning value KGi may be referred to.

  In each of the above embodiments, both the rich abnormality and the lean abnormality are prohibited, but it is also possible to adopt a configuration in which only the rich abnormality is prohibited and the lean abnormality is always permitted.

  In each of the above embodiments, the degree of fuel dilution is estimated on the assumption that fuel dilution and fuel evaporation from the lubricating oil basically occur only during engine operation. Certainly, the amounts of fuel dilution and fuel evaporation that occur during engine operation tend to be larger than when the engine is stopped, but fuel evaporation actually occurs even when the engine is stopped. There is. For this reason, for example, while measuring the engine stop time, estimating the temperature of the lubricating oil when the engine is started (or when the engine is stopped), and based on the engine stop time and the lubricating oil temperature, the amount of fuel evaporation while the engine is stopped May be estimated. Then, when estimating the fuel dilution degree, it is possible to estimate the fuel dilution degree more accurately by considering the fuel evaporation amount while the engine is stopped.

  The combustion heat generated in each fuel injection varies depending on the air-fuel ratio at the time of fuel injection, the ignition timing, etc. in addition to the intake air amount and the fuel injection amount. For this reason, in the first embodiment, when calculating the intake air amount integrated value GASUM after engine startup, and in the second embodiment, the fuel injection amount integrated value QINJSUM after engine startup is calculated. It is also effective to consider this point. More specifically, these values GASUM and QINJSUM are integrated with weighting according to the air-fuel ratio, ignition timing, etc., in order to increase the accuracy in estimating the combustion heat quantity and further the lubricating oil temperature. It is valid.

  In each of the above embodiments, the lubricating oil temperature is estimated based on the engine operating state such as the engine cooling water temperature THW, the engine starting water temperature THWST, and the fuel injection amount integrated value QINJSUM after the engine is started. For example, a sensor that directly detects the lubricating oil temperature may be provided, and the above-described various controls may be performed based on the detection result. In this case, it is desirable to detect the temperature of the lubricating oil in a temperature state highly correlated with the average temperature of the entire lubricating oil, such as the lubricating oil temperature in the oil pan 74.

1 is a schematic configuration diagram of an abnormality diagnosis device and an internal combustion engine to which the abnormality diagnosis device is applied. The flowchart which shows the process sequence of a driving | operation monitoring process. The flowchart which shows the process sequence of a driving | operation monitoring process. The timing chart which shows the operation mode etc. of a fuel dilution generation | occurrence | production flag. The flowchart which shows the process sequence of a fuel injection amount calculation process. The timing chart which shows the example of a change aspect of a feedback correction coefficient. The flowchart which shows the process sequence of an air fuel ratio feedback process. The flowchart which shows the process sequence of an air fuel ratio learning process. The flowchart which shows the process sequence of an abnormality determination process. The flowchart which shows the process sequence of a prohibition condition judgment process. The flowchart which shows the process sequence of a fuel dilution degree calculation process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Combustion chamber, 13 ... Exhaust passage, 14 ... Piston, 16 ... Head cover, 17 ... Cylinder, 18 ... Cylinder inner peripheral surface, 19 ... Crankcase, 20 ... Fuel injection valve, DESCRIPTION OF SYMBOLS 21 ... Intake valve, 22 ... Spark plug, 23 ... Exhaust valve, 24 ... Delivery pipe, 26 ... Throttle valve, 27 ... Catalyst device, 42 ... Intake air amount sensor, 43 ... Rotation speed sensor, 44 ... Accelerator sensor, 45 ... Water temperature sensor 50 ... Electronic control device (determination means, estimation means, restriction means) 52 ... Memory 60 ... Accelerator pedal 70 ... Lubrication system 72 ... Lubrication oil supply device 74 ... Oil pan 80 ... Blow-by gas reduction Device: 82 ... Communication passage, 84 ... Blow-by gas passage, 86 ... Flow control valve.

Claims (6)

Abnormality diagnosis apparatus for a cylinder injection type internal combustion engine provided with a determination means for determining abnormality of the fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control obtained based on a tendency of deviation between the actual air-fuel ratio and the target air-fuel ratio In
The air-fuel ratio learning value is obtained for each engine load region divided into a plurality of parts to compensate for the steady deviation tendency between the actual air-fuel ratio and the target air-fuel ratio, and each air-fuel ratio learning value obtained for each engine load region is determined. In-cylinder injection characterized by comprising limiting means for limiting the determination operation for determining that there is an abnormality in the determination means, provided that the difference between the engine high load range value and the engine low load range value is large. Abnormality diagnosis device for an internal combustion engine. The limiting means is that the degree of divergence is large and the air-fuel ratio correction amount is increased by a predetermined amount or more to compensate for the tendency that the actual air-fuel ratio diverges to the rich side from the target air-fuel ratio as the divergence tendency. The abnormality diagnosis device for a direct injection internal combustion engine according to claim 1, wherein a restriction is imposed on the determination operation. The abnormality diagnosis device for a cylinder injection internal combustion engine according to claim 1 or 2, wherein the restriction means adds the restriction on condition that the engine is under a low load. The abnormality diagnosis apparatus for a direct injection internal combustion engine according to any one of claims 1 to 3, wherein the limiting means prohibits abnormality determination by the determination means. The in-cylinder injection internal combustion engine according to any one of claims 1 to 3, wherein the limiting unit changes a condition for the determination unit to determine that there is an abnormality so that it is difficult to determine that the abnormality is present. Abnormality diagnosis device. The in-cylinder injection method according to any one of claims 1 to 5, wherein the limiting means limits the determination operation of the determination means that there is a rich abnormality in which the actual air-fuel ratio deviates to the rich side from the target air-fuel ratio. Abnormality diagnosis device for internal combustion engine.

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