JP2003322047A - Failure diagnosing device for intra-cylinder injection type internal-combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnosing device for an intra-cylinder injection type internal-combustion engine capable of suppressing a misdiagnosis as much as practicable resulting from a fuel dilution with a lubricating oil due to a fuel attachment to the inside surface of each cylinder when a failure diagnosis is made for its fuel injection system based upon the air-fuel ratio correction amount in the air-fuel ratio feedback control. <P>SOLUTION: The failure diagnosing device of the intra-cylinder injection type internal-combustion engine includes an electronic control device 50 which calculates the air-fuel ratio correction amount in the air-fuel ratio feedback control on the basis of the dissociation tendency of the actual air-fuel ratio from its target value and judges a failure in the fuel injection system on the basis of the air-fuel ratio correction amount. The electronic control device 50 presumes the degree of fuel dilution for the whole lubricating oil supplied to the engine 10 on the basis of the history of cold short trip. On the condition that the presumed degree of fuel dilution is large, the electronic control device 50 prohibits a judgement that there is a failure. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an abnormality diagnosing device for a cylinder injection type internal combustion engine, which is adapted to determine an abnormality of a fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control.

[0002]

2. Description of the Related Art In an internal combustion engine, feedback control of the fuel injection amount, that is, air-fuel ratio feedback control is usually performed in order to match the actual air-fuel ratio with a target air-fuel ratio such as a theoretical air-fuel ratio. Here, for example, a fuel injection valve,
If any abnormality occurs in the fuel injection system, it becomes difficult to supply a predetermined amount of fuel to the internal combustion engine, so that the engine air-fuel ratio tends to greatly deviate from the target air-fuel ratio, and the exhaust property deteriorates. And so on. Further, when such an abnormality occurs, the feedback correction amount for matching the actual air-fuel ratio with the target air-fuel ratio, that is, the air-fuel ratio correction amount becomes an extremely large value.

Therefore, when the air-fuel ratio feedback control is executed, the air-fuel ratio correction amount is monitored. When the air-fuel ratio correction amount is excessively increased, it is determined that an abnormality has occurred in the fuel injection system. An abnormality of the fuel injection system is diagnosed (for example, see Japanese Patent Laid-Open No. 2001-73853).

By the way, the internal combustion engine is provided with a blow-by gas reducing device for treating a gas leaking from the cylinder into the crank case, 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 reduction device introduces fresh air from the outside (more precisely, an air cleaner provided in the intake system) into the engine body, circulates this inside the crankcase, and finally returns it to the intake system. By performing the treatment, the blow-by gas is treated without being discharged to the outside.

The blow-by gas also contains unburned fuel components. Therefore, if this is simply returned to the intake system, the fuel injection amount will be substantially changed. However, the concentration of the fuel unburned component contained in this blow-by gas is not so high and usually does not change greatly. Therefore, such a variation in the fuel injection amount can be dealt with in the air-fuel ratio feedback control as described above, and the adverse effect thereof can be suppressed to a negligible level.

[0006]

However, unlike the intake port injection type internal combustion engine, the cylinder injection type internal combustion engine in which fuel is directly injected into the cylinder from the fuel injection valve is different from the fuel injection valve. Since the distance between the injection hole and the inner peripheral surface of the cylinder is extremely short and the structure is such that 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, atomization of the fuel in the cylinder is hard to be promoted, and therefore, a part of the injected fuel is not used for combustion and is left on the cylinder inner peripheral surface (cylinder inner peripheral surface). It remains attached. The fuel thus attached to the inner peripheral surface of the cylinder is mixed with the lubricating oil attached to the inner peripheral surface of the cylinder in order to lubricate the engine piston. as a result,
Dilution of lubricating oil with fuel, so-called fuel dilution, occurs.

Then, the lubricating oil on the inner peripheral surface of the cylinder diluted with the fuel is scraped off as the engine piston moves up and down, and the crankcase (to be exact, an oil pan formed as a part thereof). After being returned to the internal combustion engine, it is used again for lubrication of the internal combustion engine such as the engine piston. Therefore, when such fuel dilution of the lubricating oil occurs frequently, the proportion 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 proportion of the fuel contained in the lubricating oil is increased in this way, a large amount of the fuel is evaporated from the lubricating oil, and the fuel concentration of the blow-by gas is greatly increased. Then, when the fuel injection amount is relatively small, especially when the engine load is low, and blow-by gas whose fuel concentration has greatly increased is introduced into the intake system, this causes the air-fuel ratio to rise. There is a possibility that the air-fuel ratio correction amount of the feedback control is excessively increased, and that the fuel injection system may be erroneously diagnosed as having an abnormality, even though no abnormality has occurred in the fuel injection system.

The present invention has been made in view of such a conventional situation, and an object thereof is to attach fuel to the inner peripheral surface of a cylinder when diagnosing an abnormality in a fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control. An object of the present invention is to provide an abnormality diagnosis device for a cylinder injection type internal combustion engine, which can suppress erroneous diagnosis caused by fuel dilution of lubricating oil due to the above.

[0011]

[Means for Solving the Problems] Means and effects for solving the above problems will be described below. Claim 1
The invention described is an in-cylinder injection internal combustion engine equipped with a determination means for determining an abnormality in the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control that is determined based on the deviation tendency between the actual air-fuel ratio and the target air-fuel ratio. In an engine abnormality diagnosis device, an estimating means for estimating the fuel dilution degree of the entire lubricating oil used for lubrication of the internal combustion engine, and the determining means of the determining means under the condition that the estimated fuel dilution degree is large. A limiting means is provided for limiting the operation of determining that there is an abnormality.

According to this structure, the determining means determines the abnormality of the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control. Further, the estimating means estimates the fuel dilution degree of the entire lubricating oil used for lubricating the internal combustion engine. Then, when the estimated fuel dilution degree of the entire lubricating oil is large and therefore the fuel evaporation amount from the lubricating oil is increasing, the limiting operation limits the determination operation for determining that the determination means is abnormal. That is, in this case, it is more difficult to determine that there is an abnormality, as compared with the case where the fuel dilution degree is small. Therefore, it is possible to suppress the erroneous diagnosis due to the fuel dilution of the lubricating oil in the abnormality diagnosis of the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control.

Further, when the fuel evaporation amount from the lubricating oil is increased due to the fuel dilution, the actual air-fuel ratio tends to deviate to the rich side from the target air-fuel ratio unless an abnormality occurs in the fuel injection system. (Rich tendency) is likely. On the other hand, in this case, it is extremely unlikely that the actual air-fuel ratio tends to deviate to the lean side from the target air-fuel ratio (lean tendency). Therefore, even if the air-fuel ratio correction amount calculated based on such a deviation tendency increases (to be precise, the deviation amount from the reference value of the air-fuel ratio correction amount is large), it increases the fuel evaporation amount from the lubricating oil. If it is caused by the fact that it is being performed, it will increase to the side that compensates the rich tendency. On the contrary, when the air-fuel ratio correction amount increases to the side that compensates the lean tendency, it is considered that it is due to the abnormality of the fuel injection system.

The invention according to claim 2 takes this point into consideration, and in the abnormality diagnosing device for a direct injection internal combustion engine according to claim 1, the limiting means has a large estimated fuel dilution degree and The air-fuel ratio correction amount limits the determination operation on the condition that the actual air-fuel ratio as the deviation tendency is increased by a predetermined amount or more on the side that compensates for the tendency to deviate to the rich side from the target air-fuel ratio. There is.

In the same construction, in addition to the condition relating to the fuel dilution degree, the condition for adding the above restriction is that the air-fuel ratio correction amount further increases by a predetermined amount or more on the side of compensating the rich tendency. When the fuel evaporation amount due to the fuel dilution increases and the difference between the air-fuel ratios actually occurs due to the increase, the determination operation is limited. Therefore, for example, even when the fuel dilution degree is large, when the air-fuel ratio correction amount compensates for the lean tendency, in other words, when the fuel dilution degree is large and there is no risk of erroneous diagnosis, Judgment is never prohibited. As a result, it is possible to prevent the above determination operation from being unnecessarily limited.

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 estimating means estimates the fuel dilution degree based on the operation history of the internal combustion engine. It is supposed to do.

The degree of fuel dilution of the entire lubricating oil changes according to the operation history of the internal combustion engine up to that point. For example, if the internal combustion engine is started in a situation where the engine temperature is low and then stopped before the engine temperature rises sufficiently, that is, when a so-called cold short trip is repeated, the fuel dilution degree is greatly increased. Become. On the other hand, if the internal combustion engine is operated for a long period even after the warm-up of the internal combustion engine is completed, the fuel contained in the lubricating oil gradually evaporates during the operation, so that the fuel dilution degree decreases. Therefore, by referring to such an operation history of the internal combustion engine, the fuel dilution degree of the entire lubricating oil can be estimated.

Specifically, according to the invention described in claim 4, the estimating means monitors that the internal combustion engine is operated under the condition that the fuel dilution degree increases, and the monitoring history thereof. By adopting a configuration in which the fuel dilution degree is estimated based on the above, it is possible to accurately estimate the fuel dilution degree when the fuel dilution degree of the entire lubricating oil increases.

Here, for example, when the engine temperature at engine startup is high, fuel adhesion to the inner peripheral surface of the cylinder does not occur in the first place, so the degree of fuel dilution of the entire lubricating oil does not increase. Therefore, in the invention according to claim 4, for example, the engine temperature at the time of starting the engine is monitored, and when it is below a predetermined temperature, it is determined that the internal combustion engine has been operated under the condition that the fuel dilution degree increases. It is also possible to do so.

However, even if the engine temperature at engine start is low, if the internal combustion engine is continuously operated for a long period of time thereafter, the temperature in the cylinder rises and fuel adheres to the inner surface of the cylinder. Will be suppressed. Furthermore, the temperature of the lubricating oil gradually rises due to the combustion heat generated in the cylinder, and the fuel evaporated from the lubricating oil also increases as the temperature rises.

Therefore, if the time from when the internal combustion engine is started to when it is stopped is increased to some extent, even if the degree is temporarily increased by the fuel dilution that occurs in the initial stage of engine operation, the subsequent engine operation is performed. The fuel diluting degree gradually decreases as the fuel evaporates from the lubricating oil. If the increase in the fuel dilution degree that occurred in the initial stage of engine operation is offset or exceeded by such a decrease in the fuel dilution degree, the internal combustion engine is operated in a situation where the fuel dilution degree increases. There is no need to keep a history of what was done.

Therefore, in the invention as set forth in claim 4, for example, the engine operating time from the start of the engine to the stop of the engine is measured, and the engine temperature at the engine starting is below a predetermined temperature and the engine operating time is a predetermined value. It is also possible to judge that the internal combustion engine has been operated under the situation where the fuel dilution degree increases when the following is true.

Even if the internal combustion engine is started and stopped for the same period of time, if a large amount of fuel is used for engine combustion during that time, the temperature in the cylinder may rise early. Become. Therefore, the fuel adhesion on the inner peripheral surface of the cylinder can be suppressed at an earlier stage, and the evaporation of the fuel due to the temperature rise of the lubricating oil can be further promoted. The rising speeds of the in-cylinder temperature and the lubricating oil temperature have a correlation with the total combustion heat quantity generated in the cylinder after the engine is started. Therefore, in order to accurately determine whether or not the internal combustion engine has been operated under the condition where the fuel dilution degree increases, it is necessary to monitor the total combustion heat amount generated in the cylinder between the engine start and the engine stop. Considered desirable.

The invention according to claim 5 focuses on this point, and in the abnormality diagnosing device for a cylinder injection type internal combustion engine according to claim 4, the estimating means includes the cylinder between the engine start and the engine stop. The total combustion heat quantity generated in the engine is estimated based on the engine operating state, and when the engine temperature at engine startup is below a predetermined temperature and the estimated total combustion heat quantity is below a predetermined quantity, the fuel dilution degree of It is supposed that it is determined that the internal combustion engine has been operated under the increasing situation.

According to this structure, it is accurately judged that the internal combustion engine is operated under the condition that the fuel dilution degree of the entire lubricating oil increases, and the fuel dilution degree of the entire lubricating oil increases based on the judgment. It becomes possible to more accurately estimate this in the case of doing. As the engine temperature, for example, it is desirable to directly detect the cylinder temperature, but it is possible to estimate this based on, for example, the engine cooling water temperature at the engine start, the intake air temperature, the outside air temperature, or a combination thereof. it can.

Further, in the same construction, when the engine temperature at engine startup is lower than the predetermined temperature and the total amount of heat of combustion is lower than the predetermined amount, the internal combustion engine is operated under the condition that the degree of fuel dilution increases. I try to judge that, but here,
It is also possible to employ a configuration in which the above-mentioned predetermined amount that is compared with the total combustion heat amount is variably set according to the engine temperature at the time of engine startup. That is, even if the engine temperature at the time of engine start is equal to or lower than the above-mentioned predetermined temperature, when it is relatively high, the increase in the fuel dilution degree that occurs in the initial stage of engine operation becomes small, so it is only offset or exceeded. The total amount of heat required for combustion is inevitably low. Therefore, with respect to the above-mentioned predetermined amount to be compared with the total combustion heat amount, the configuration is set such that the higher the engine temperature at the time of engine startup, the smaller this value is set, and the internal combustion engine is operated under the condition that the fuel dilution degree increases. It is extremely effective in making accurate decisions.

The fact that the total amount of heat of combustion generated in the cylinder from the engine start to the engine stop is less than or equal to a predetermined amount is, for example, from the engine start to the engine stop as in the invention according to claim 6. This can be determined based on whether the intake air amount integrated value or the fuel injection amount integrated value during the period is less than or equal to a predetermined value. In addition, the combustion heat generated in each cylinder by each fuel injection is, in addition to the intake air amount and the fuel injection amount,
It also changes depending on the air-fuel ratio at the time of fuel injection and the ignition timing.
Therefore, for example, a method in which the intake air amount and the fuel injection amount at that time are weighted based on the air-fuel ratio and the ignition timing and integrated, is also effective in accurately estimating the total combustion heat amount.

According to a seventh aspect of the present invention, in the abnormality diagnosing device for a direct injection internal combustion engine according to any of the fourth to sixth aspects, the estimating means has a temperature of the lubricating oil or a correlation with the temperature. It is determined whether or not the fuel dilution degree is reduced based on a parameter, and is counted up when a history indicating that the internal combustion engine is operated under the situation where the fuel dilution degree is increased occurs. The fuel dilution degree is estimated based on the size of the counter value that is gradually counted down when it is determined that the fuel dilution degree is decreasing.

As described above, when the operation of the internal combustion engine in a situation where the fuel dilution degree increases, for example, a cold short trip is frequently repeated, the fuel dilution degree of the entire lubricating oil gradually increases accordingly. Come to do. On the other hand, when the operation of the internal combustion engine is performed for a long period of time and the temperature of the lubricating oil rises, the evaporation amount of the fuel contained in the lubricating oil also increases, so that the fuel dilution degree of the entire lubricating oil decreases. The degree of fuel dilution gradually decreases over time.

According to the above structure of the present invention, since the counter value that changes according to the increase or decrease of the fuel dilution degree is set, the fuel dilution degree is further increased based on the magnitude of the counter value. You will be able to estimate accurately.

According to an eighth aspect of the present invention, in the abnormality diagnosing device for a direct injection internal combustion engine according to the first or second aspect, the estimating means correlates with the amount of fuel adhering to the inner peripheral surface of the cylinder by fuel injection. The increase rate of the fuel dilution degree is calculated on the basis of the parameter, and the fuel dilution degree is estimated by sequentially updating and learning the fuel dilution degree based on the calculated increase rate. I am trying.

The degree of fuel dilution of the entire lubricating oil is obtained by diluting the lubricating oil adhering to the inner peripheral surface of the cylinder by the fuel injection and mixing this with the remaining lubricating oil. Progress gradually. Therefore, the degree of progress of fuel dilution, that is, the rate of increase of the degree of fuel dilution can be calculated based on the amount of fuel that adheres to the inner peripheral surface of the cylinder due to fuel injection (correctly, a parameter having a correlation with this).

Therefore, according to the above-mentioned structure of the eighth aspect, the present value of the fuel dilution degree is successively updated based on this increasing speed, and this value is learned as a new fuel dilution degree value. This makes it possible to accurately estimate this as the degree of fuel dilution increases.

Although it is difficult to directly detect the amount of fuel adhered to the inner peripheral surface of the cylinder, the fuel injection amount, the fuel injection timing, the engine temperature, etc., can be detected. This can be easily obtained based on a parameter having a correlation with the fuel adhesion amount or a combination of these parameters. By the way, the fuel adhesion amount on the inner peripheral surface of the cylinder is (a) the fuel injection amount is large,
(B) The fuel injection timing is set at a time when the engine piston is closer to the bottom dead center side, and (c) the engine temperature is low, the tendency tends to increase. Therefore, each of these tendencies is taken into consideration when determining the fuel adhesion amount on the inner peripheral surface of the cylinder.

The invention according to claim 10 is the invention according to claim 8 or 9.
In the in-cylinder injection type internal combustion engine abnormality diagnosing device described above, the estimating means further estimates the amount of fuel evaporated from the entire lubricating oil based on the temperature of the lubricating oil or a parameter having a correlation with the temperature, and the estimation is performed. Calculating a decrease rate of the fuel dilution degree based on the fuel evaporation amount that is performed, and sequentially updating and learning the fuel dilution degree based on the calculated decrease rate and the calculated increase rate. According to the above, the fuel dilution degree is estimated.

The degree of fuel dilution of the entire lubricating oil is gradually eliminated by the temperature of the lubricating oil rising due to engine combustion heat and the like, and the fuel contained in the lubricating oil evaporating as the temperature rises. Therefore, the degree of elimination of fuel dilution, that is, the rate of decrease in the degree of fuel dilution can be calculated based on the temperature of the lubricating oil or a parameter having a correlation with the same temperature.

Therefore, according to the above structure of the tenth aspect, the current value of the fuel dilution degree is successively updated based on the increasing rate of the fuel dilution degree and the decreasing rate thereof,
By learning this as a new fuel dilution degree value, it becomes possible to more accurately estimate both the increase and decrease of the fuel dilution degree.

According to the eleventh aspect of the present invention, there is provided a determining means for determining an abnormality of the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control which is obtained based on the deviation tendency between the actual air-fuel ratio and the target air-fuel ratio. In a cylinder injection type internal combustion engine abnormality diagnosis device, in order to compensate for the steady deviation tendency of the actual air-fuel ratio and the target air-fuel ratio, the air-fuel ratio learning value is obtained for each engine load region divided into a plurality, Regarding each air-fuel ratio learning value obtained for each engine load region, the determination operation to determine that there is an abnormality in the determination means is limited on the condition that the degree of deviation between the value in the high engine load region and the value in the low engine load region is large. A limiting means for adding is added.

When the fuel evaporates from the lubricating oil, the rate of change in the amount of fuel evaporation is extremely small as compared with the rate of change in the fuel injection amount that accompanies changes in the engine operating state. Therefore, the correction amount for compensating for 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. Like

Further, when the engine load is low, the amount of fuel injected from the fuel injection valve is relatively small, so when the fuel evaporates from the lubricating oil, this fuel accounts for the amount of fuel supplied to the internal combustion engine. The rate of evaporation becomes large compared to when the engine is under high load operation. Therefore, when the engine operating state is on the low load side and when it is on the high load side, there is a difference in the tendency of deviation.

In the invention described in claim 11, this point is taken into consideration, and there is a large degree of deviation between the value in the engine high load region and the value in the engine low load region regarding the air-fuel ratio learning value. The condition is set so as to limit the determination operation for determining that the determination means is abnormal. Therefore, it is possible to accurately determine that the fuel evaporation amount from the lubricating oil is increasing, and to limit the determination operation for determining that there is an abnormality in the determining means on the condition that the amount of fuel evaporation is increasing. as a result,
In the abnormality diagnosis of the fuel injection system based on the air-fuel ratio correction amount of the air-fuel ratio feedback control, it is possible to suppress the erroneous diagnosis due to the fuel dilution of the lubricating oil as much as possible.

The deviation tendency is, for example, the deviation (KGH-KGL) between the value KGH in the high engine load range and the value KGL in the low engine load range or the ratio (KGH / KGL) of the air-fuel ratio learning value. This can be determined by). Further, even if the fuel is not evaporated from the lubricating oil, if there is a tendency of deviation peculiar to the engine between the value KGH in the high engine load range and the value KHL in the low engine load range. It is also effective to correct the deviations and ratios described above so as to cancel the deviation tendency peculiar to the engine.

The invention according to claim 12 is the same as claim 1
In the in-cylinder injection internal combustion engine abnormality diagnosing device described in 1, the limiting means has a large deviation degree and the air-fuel ratio correction amount deviates to a rich side from a target air-fuel ratio as the deviation tendency. It is assumed that the judgment operation is limited on the condition that the tendency is compensated for by a predetermined amount or more.

According to this construction, in addition to the condition concerning the deviation, the fuel evaporation amount due to the fuel dilution increases, and the deviation of the air-fuel ratios actually occurs due to the increase, as in the invention of claim 2. When the above occurs, the determination operation is limited, so that the determination operation can be prevented from being unnecessarily limited.

The erroneous diagnosis concerning the abnormality diagnosis of the fuel injection system becomes most remarkable when the fuel injection amount from the fuel injection valve becomes relatively small. Therefore, in the invention according to claim 13, in the abnormality diagnosing device for a direct injection internal combustion engine according to any one of claims 1 to 12, the restriction means is provided under the condition that the engine is under a low load. It is supposed to be added.

According to this configuration, since the limitation relating to the abnormality determination is applied under the condition that the engine is under low load, erroneous diagnosis can be suppressed as much as possible when the engine is under low load. It becomes possible to avoid unnecessarily limiting the operation of determining that there is an abnormality when the engine load is high.

Further, as a specific mode for limiting the judgment operation by the judgment means for judging that there is an abnormality,
For example, as in the invention described in claim 14, in the abnormality diagnosing device for a direct injection internal combustion engine according to any one of claims 1 to 13, the limiting means prohibits the abnormality determination by the determining means, According to the invention described in claim 15 or the structure described in claim 15,
In the cylinder injection type internal combustion engine abnormality diagnosis device according to any one of the above, the limiting means changes the condition for determining that the determination means is abnormal so that it is difficult to determine that the abnormality is present, Such a configuration can be adopted.

According to the structure described in claim 14, erroneous diagnosis can be suppressed more reliably. Further, according to the configuration of claim 15, by changing the condition for the determination means to determine that there is an abnormality, the erroneous diagnosis is performed while avoiding excessive restriction of the determination operation that determines that there is an abnormality. Can be suppressed.

Further, as described above, when the fuel dilution degree becomes large and the fuel evaporation amount from the lubricating oil increases, the actual air-fuel ratio becomes the target air-fuel ratio if no abnormality occurs in the fuel injection system. There is a high possibility that it will tend to deviate to the rich side of the fuel ratio. Therefore, even if an abnormality (rich abnormality) occurs in which the actual air-fuel ratio largely deviates to the rich side from the target air-fuel ratio, is this due to the abnormality of the fuel injection system that is the target of abnormality determination, or It is difficult to determine whether the cause is that the amount of fuel evaporated from the lubricating oil is increasing.

On the other hand, when there is an abnormality (lean abnormality) in which the actual air-fuel ratio largely deviates to the lean side from the target air-fuel ratio even though the fuel evaporation amount from the lubricating oil is increasing. Is highly likely to have an abnormality that makes it difficult to supply a predetermined amount of fuel because the fuel injection capability of the fuel injection system is low, and is unlikely to cause a false diagnosis.

In this respect, the invention according to claim 16 is the abnormality diagnosing device for a direct injection internal combustion engine according to any one of claims 1 to 15, wherein the limiting means has an actual air-fuel ratio that is greater than a target air-fuel ratio. Also limits the determination operation of the determination means for determining that there is a rich abnormality that deviates to the rich side.

According to this configuration, the misdiagnosis of the rich abnormality of the fuel injection system caused by the fuel dilution of the lubricating oil can be suppressed as much as possible, while the lean abnormality which is hard to be misdiagnosed can be promptly determined. However, it becomes possible to diagnose that there is an abnormality in the fuel injection system.

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 the engine cooling water temperature. Good. In addition, regarding this lubricating oil temperature, its initial value is estimated based on the engine temperature (for example, engine cooling water temperature) at engine startup,
Estimate the amount of increase based on the total combustion heat after engine start (for example, it is calculated from the intake air amount integrated value or the fuel injection amount integrated value), and find the current lubricating oil temperature based on these initial values and the amount of increase. You may do it.

[0054]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] The first embodiment of the present invention will be described below.

FIG. 1 shows a schematic structure of an abnormality diagnosis device according to this embodiment, an internal combustion engine 10 to be diagnosed, a lubricating 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 an in-cylinder internal combustion engine in which fuel is directly injected from the fuel injection valve 20 into the 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 capable of reciprocating, and the combustion chamber 12 is partitioned by the top surface of the piston 14 and the cylinder inner peripheral surface 18. Has been done.

An intake passage 11 and an exhaust passage 13 are connected to the combustion chamber 12, respectively. A throttle valve 26 is provided in the middle of the intake passage 11, and the intake air introduced into the combustion chamber 12 is metered by the throttle valve 26. When the intake valve 21 is opened, the combustion chamber 1
The intake air introduced into No. 2 is mixed with fuel injected from the fuel injection valve 20 to form an air-fuel mixture. Then, this mixture is exploded and burned by ignition of the ignition plug 22, and then discharged from the combustion chamber 12 to the exhaust passage 13 when the exhaust valve 23 is opened. A catalyst device 27 having an exhaust gas purification function is provided in the exhaust passage 13.

Further, the fuel injection valve 20 is the delivery pipe 2
The fuel is supplied from the delivery pipe 24 at a predetermined pressure. Fuel having a predetermined pressure is supplied to the delivery pipe 24 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.

The lubricating system 70 of the internal combustion engine 10 has 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 to the cylinder inner peripheral surface 18 from the mechanism. afterwards,
The lubricating oil is scraped down from the inner peripheral surface 18 of the cylinder as the piston 14 reciprocates, and finally returned to the oil pan 74.

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

Further, the internal combustion engine 10 has a blow-by gas reducing device 8 for scavenging blow-by gas existing inside the crank case 19 or the like and processing the blow-by gas.
0 is provided. This blow-by gas reduction device 80
Is a communication passage 82 that connects a portion of the intake passage 11 upstream of the throttle valve 26 and the inside of the head cover 16, and a throttle valve 26 in the intake passage 11.
A blow-by gas passage 84 that connects the downstream side portion and the inside of the head cover 16 is provided.

The intake passage 11 is accompanied by the operation of the internal combustion engine 10.
When intake negative pressure is generated inside, fresh air is introduced into the head cover 16 through the communication passage 82. Then, the fresh air is circulated inside the internal combustion engine 10 while being mixed with the blow-by gas, 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 reducing device 80 without being discharged to the outside. A flow control valve 8 for adjusting the flow rate of blow-by gas in the blow-by gas passage 84 is provided in the middle of the blow-by gas passage 84.
6 is provided.

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 near the stoichiometric air-fuel ratio (for example, "A / F = 12 to 15"), and the fuel injection timing is during the intake stroke. Is set to (intake stroke injection).

On the other hand, during low load operation, the combustion mode is set to stratified charge combustion. During this stratified combustion, the air-fuel ratio A / F is leaner than the stoichiometric air-fuel ratio (for example, "A / F
= 17-40 "), the fuel injection amount and the like are controlled, and the fuel injection timing is set to the latter stage of the compression stroke (compression stroke injection).

Further, during 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. . In this weakly stratified combustion, the combustion is performed with a weaker degree of stratification than in the stratified combustion. During the weak stratified charge 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”), and the fuel injection is performed in the intake stroke and It is performed in both strokes of the compression stroke (two-stage injection).

When the engine is cold (for example, the engine cooling water temperature TH
During the period when W becomes equal to or lower than the predetermined temperature THWL), atomization of the injected fuel tends to be difficult to be promoted. Therefore, 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, the period from fuel injection to ignition is secured longer than in stratified charge combustion in which compression stroke injection is executed, and atomization of injected fuel is promoted as much as possible.

After the engine is warmed up (for example, the engine cooling water temperature T
HW is equal to or higher than a predetermined temperature THWL), and when a predetermined condition is satisfied, such as when the learning of the air-fuel ratio learning value is not completed during the current engine operation even during low load operation. Is set to a homogeneous combustion regardless of the engine load state.

The control relating to such combustion mode is performed by the electronic control unit 50. This electronic control unit 50
Is a unit that collectively executes various controls in the internal combustion engine 10 such as air-fuel ratio control and fuel injection control. In addition to the arithmetic unit, the drive circuit, etc., the calculation results of various controls and the function map used for the calculation A memory 52 for storing the above information is provided.

Further, the internal combustion engine 10 is provided with various sensors for detecting its operating state. For example,
An intake air amount sensor 42 for detecting the 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) of the internal combustion engine 10 is provided near the output shaft (not shown) of the internal combustion engine 10. Accelerator pedal 60
An accelerator sensor 44 for detecting the amount of depression (accelerator opening) is provided near the position. A water temperature sensor 45 that detects the temperature of the engine cooling water is attached to the cylinder block (not shown). Further, an oxygen sensor 46 for detecting the air-fuel ratio based on the oxygen concentration of the exhaust gas is attached on the upstream side of the catalyst device 27 in the exhaust passage 13. The detection results of each of these sensors 42 to 46 are
It is taken into the electronic control unit 50. Then, 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 during homogeneous combustion (fuel injection amount calculation process, air-fuel ratio feedback control, air-fuel ratio learning process), fuel injection valve 20 and delivery pipe 24. Alternatively, a control procedure (abnormality determination processing, prohibition condition determination processing) for diagnosing an abnormality related to the fuel injection system of the internal combustion engine 10, such as a fuel pump that supplies fuel to the fuel pump, will be described.

When the engine is cold, the fuel injection valve 20
A part of the fuel injected from the combustion chamber 12 into the combustion chamber 12 is
It has been described above that if the fuel adheres to No. 8 and the fuel is diluted in the entire lubricating oil due to such fuel adhesion and the fuel evaporation amount increases, an erroneous diagnosis may be 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, the history of the internal combustion engine 10 being operated under the condition that the fuel dilution degree increases, specifically, the cold short trip is performed. Through the process for monitoring the history (operation history monitoring process), it is monitored that such fuel dilution of the entire lubricating oil occurs, and that this is actually affecting the air-fuel ratio feedback control. Then, under such a situation, the abnormality diagnosis control is prohibited so as to avoid erroneous diagnosis that the fuel injection system is abnormal.

[1. Operation History Monitoring Process] First, the operation history monitoring process will be described. The flowcharts of FIGS. 2 and 3 show the processing procedure of the driving history monitoring processing.
The electronic control unit 50 repeatedly executes the series of processes shown in each of these figures at a predetermined time period T. Also,
The timing chart of FIG. 4 shows an example of the control mode based on this processing. During this series of processes, it is determined whether the operation of the internal combustion engine 10 has been stopped (step S100 in FIG. 2). Incidentally, electric power is continuously supplied to the electronic control unit 50 after the operation of the internal combustion engine 10 is stopped until a predetermined period of time elapses, and the electronic control unit 50 is in a state capable of operating. Electronic control unit 50
Performs the post-processing required for the next engine operation, such as storing and holding the execution results of various controls during engine operation in the memory 52 before the elapse of a predetermined period after the engine is stopped.

When it is judged that the engine is stopped (step S100: YES, the timing t in FIG. 4).
2, t4, t6), and then the value of the engine cooling water temperature THW at the time of engine startup (hereinafter referred to as "engine starting water temperature THWST") is read from the memory 52, and this is the predetermined temperature T.
It is determined whether or not it is below HWL (step S11).
0). Here, the combustion is ended without being supplied to the combustion while a part of the injected fuel is attached to the inner peripheral surface 18 of the cylinder, that is, the engine is started under the situation where the above-mentioned fuel dilution is concerned. I try to judge whether or not.

Here, when it is determined that the engine starting water temperature THWST is equal to or lower than the predetermined temperature THWL (step S
110: YES), that is, when the engine is started this time under the condition that fuel dilution may occur (timing t1, t3, t5, t7 in FIG. 4), further intake after engine start The integrated air amount GASUM is a predetermined amount GASUML
It is determined whether or not the following (step S120).

Even if the engine starting water temperature THWST is low, if the internal combustion engine 10 is continuously operated for a long period of time thereafter, the temperature of the combustion chamber 12 rises and atomization of the injected fuel is promoted. As a result, the cylinder inner peripheral surface 18
The adherence of fuel is also suppressed accordingly. Further, the temperature of the lubricating oil gradually rises due to the heat of combustion of the engine, and the amount of fuel evaporated from the lubricating oil also increases as the temperature rises.

Therefore, even if the engine starting water temperature THWST is low and the fuel dilution degree temporarily increases at the beginning of engine operation, the fuel dilution degree is increased by the evaporation of fuel from the lubricating oil during the subsequent engine operation. Will gradually decrease. If the increase in the fuel dilution degree that occurs in the initial stage of engine operation is offset or exceeds the decrease due to the decrease in the fuel dilution degree, the internal combustion engine 10 is in a situation where the fuel dilution degree increases. It is not necessary to keep a history that the vehicle has been operated, that is, a cold short trip has been made.

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 amount of fuel injection set based on this, and the larger the amount of combustion air, the greater the amount of combustion heat. Tend to do. Therefore, it is considered that the combustion heat quantity generated during the engine operation period has a correlation with the integrated value GASUM of the intake air quantity.

Therefore, by appropriately setting the predetermined amount GASUML in step S120, the temperature of the lubricating oil rises during the engine operation and the fuel evaporates, which is caused at the beginning of the engine operation due to the reduction of the fuel dilution degree. It can be appropriately determined that the increase in the fuel dilution degree is offset or exceeds the increase.

Incidentally, the step S120 is always negatively determined after the execution of the stratified charge combustion is permitted as the engine cooling water temperature rises. That is,
In 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 during which the intake stroke injection is executed is substantially compared with the predetermined amount GASUML. .

When it is determined in step S120 that the intake air amount integrated value GASUM is less than or equal to the predetermined amount GASUML (step S120: YES), it is determined that the current engine operation corresponds to a cold short trip.
Then, in this case, the dilution degree counter value C is incremented by the predetermined amount a (step S130, timings t2, t4 and t6 in FIG. 4). The dilution degree counter value C indicates the degree of progress of dilution of the entire lubricating oil with the fuel. The dilution degree counter value C has a larger value as the fuel dilution degree increases, and has a smaller value as the fuel dilution degree decreases. Thus, it is operated through this series of processing.
The count-up process of step S130 is executed only once after the engine is stopped, on the condition that the process is not yet performed after the engine is stopped.

When the dilution degree counter value C is counted up in this manner, it is next determined whether or not the dilution degree counter value C is equal to or larger than the determination value CH (step S1).
40). 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 large, and when the fuel dilution further proceeds, the air-fuel ratio feedback control is performed. Consequently, it is determined that there is a possibility that an adverse effect may occur on the abnormality determination processing executed based on the air-fuel ratio correction amount under 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, setting the fuel dilution occurrence flag XS 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 manner, this series of processing is temporarily terminated.

On the other hand, if it is determined in the previous step S100 that the internal combustion engine 10 is operating (step S100: NO), then it is determined whether the engine cooling water temperature THW is equal to or higher than the predetermined temperature THWH. It is determined (step S160 in FIG. 3).

Here, by comparing the engine cooling water 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, and finally, with the temperature rise. Therefore, it is determined whether or not the amount of fuel evaporated from the entire lubricating oil has risen to a predetermined amount and the degree of dilution of the fuel is reduced. That is,
If the engine cooling water temperature THW is rising, it can be considered that the combustion heat amount generated after the engine is started is large. For this reason,
It can be simply determined that the temperature of the entire lubricating oil has risen due to the heat of combustion, and the amount of fuel evaporation has also increased to such an extent that the degree of fuel dilution is reduced.

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

On the other hand, the engine cooling water temperature THW is equal to the predetermined temperature TH.
When it is determined that it is less than WH (step S17
0: NO), this countdown process is not executed.
Next, the dilution degree counter value C is the judgment value CL (<the judgment value C
H) or less is determined (step S18)
0). Here, when the dilution degree counter value C is less than or equal to the determination value CL (step S180: YES), the fuel dilution degree of the entire lubricating oil is small, and therefore fuel dilution is temporarily caused by fuel injection and the lubricating oil Even if the overall fuel dilution degree progresses, it is determined that the adverse effect of this on the abnormality determination processing 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 manner, this series of processing is temporarily terminated.

On the other hand, the dilution degree counter value C is the judgment value CL.
If the above is the case (step S180: NO), the operation of the fuel dilution occurrence flag XS is not performed, and this series of processing is temporarily terminated.

On the other hand, each step S11 in FIG.
0, S120, when it is determined that the engine start water temperature THWST exceeds the predetermined temperature THWL (step S110: NO), or that the intake air amount integrated value GASUM after the engine starts exceeds the predetermined amount GASUML. When it is determined (step S120: NO), it is determined that the current engine operation does not correspond to the cold short trip. Then, in these cases, the series of processes is once ended without performing the count-up process of the dilution degree counter value C.

When it is determined in step S140 that the dilution degree counter value C is less than the determination value CH (step S140: NO), the current engine operation corresponds to a cold short trip, and therefore the dilution is performed. Although the degree counter value C has been counted up, it is determined that the adverse effect of the fuel dilution degree on the abnormality determination processing has not yet reached a level that cannot be ignored. Then, in this case, the series of processes is once ended 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. The series of processing shown in this flowchart is performed by the electronic control unit 50.
Is repeatedly executed with a predetermined cycle.

In this series of processing, first, the intake air amount,
Parameters such as the engine rotation speed and the engine cooling water temperature THW indicating the current engine operating state are read (step S2).
00). Then, the basic fuel injection amount QBASE is calculated based on these parameters (step S21).
0).

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 formula (1), "FAF" is the target air-fuel ratio. Is a feedback correction coefficient for compensating for the temporary deviation tendency of the actual air-fuel ratio from the theoretical air-fuel ratio. On the other hand, "KG
“I” is an air-fuel ratio learning value for compensating for the steady deviation tendency of the actual air-fuel ratio from 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 areas.
Specifically, the engine load region is divided into five regions Ri (i = 1 to 5) based on the amount of intake air.

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 the correspondence with this region Ri. That is, in the calculation of the fuel injection amount shown in the above equation (1), when the engine load region is in the region R3, for example, the air-fuel ratio learning value K corresponding to it
G3 is selected.

The air-fuel ratio learning value KGi is obtained through the air-fuel ratio feedback process and the air-fuel ratio learning process described later. At this time, when the actual air-fuel ratio tends to deviate from the stoichiometric air-fuel ratio due to the increase in the fuel dilution degree and the increase in the fuel evaporation amount from the lubricating oil, the same tendency is given to this air-fuel ratio learning value KGi. Will be reflected in.

When the final fuel injection amount QINJ is calculated in this way, this series of processing is temporarily terminated. [3. Air-Fuel Ratio Feedback Processing] Next, the air-fuel ratio feedback processing will be described with reference to FIGS. 6 and 7. FIG. 7 is a flowchart showing a procedure for calculating the feedback correction coefficient FAF, and the series of processes shown in the flowchart is repeatedly executed by the electronic control unit 50 at a predetermined cycle.

In this series of processes, first, it is judged whether or not the conditions for performing the air-fuel ratio feedback process are satisfied (step S300). Here, as the execution condition of the air-fuel ratio feedback process, for example, (condition 1) the engine is not started (condition 2) fuel cut is not performed (condition 3), the engine cooling water temperature THW is equal to or higher than a predetermined temperature (condition 4) The activation process of the oxygen sensor 46 has been completed.

When at least one of these conditions 1 to 4 is not satisfied, it is determined that the execution condition of the air-fuel ratio feedback process is not satisfied (step S).
300: NO). In this case, the feedback correction coefficient FAF is set to "1.0" (step S
340), this series of processing is temporarily terminated. Therefore,
In this case, the feedback control of the fuel injection amount based on the feedback correction coefficient FAF is not substantially performed.

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

Here, the output voltage Vox is the reference voltage Vr.
When it is less than (step S302: YES), the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, and the air-fuel ratio identification flag XOX is set to "0" (step S31).
0).

Next, the value of the air-fuel ratio identification flag XOX and the value of the same air-fuel ratio identification flag XOX in the previous control cycle XOXO.
(Hereinafter, simply referred to as “previous value XOXO”) is compared (step S312). If they match (step S312: YES), it is determined that the state in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio is continuing. Then, in this case, a predetermined integration 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 S31).
4).

On the other hand, if the value of the air-fuel ratio identification flag XOX is different from the previous value XOXO (step S31).
2: NO), it is determined that the air-fuel ratio is reversed from the value on the rich side to the value on the lean side with respect to the stoichiometric air-fuel ratio. Then, in this case, a predetermined skip amount A (A> 0) is added to the feedback correction coefficient FAF,
The added value (= FAF + A) is set as a new feedback correction coefficient FAF (step S316).
It should be noted that the skip amount A is set to a sufficiently large value as compared with the previous integration amount a.

On the other hand, the output voltage V of the oxygen sensor 46
When ox is equal to or higher than the reference voltage Vr (step S3
02: NO), and the air-fuel ratio is richer than the stoichiometric air-fuel ratio, and the air-fuel ratio identification flag XOX is set to "1" (step S320).

Next, the value of the air-fuel ratio identification flag XOX and its previous value XOXO are compared (step S322).
Then, if they match (step S3
22: YES), it is determined that the state in which the air-fuel ratio is on the rich side of the stoichiometric air-fuel ratio is continuing. Then, 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, if the value of the air-fuel ratio identification flag XOX is different from the previous value XOXO (step S32).
2: NO), it is judged that the air-fuel ratio is reversed from the lean side value to the rich side value with respect to the stoichiometric air-fuel ratio. Then, in this case, a predetermined skip amount B (B> 0) is subtracted from the feedback correction coefficient FAF, and the subtracted value (= FAF-B) is set as a new feedback correction coefficient FAF (step S32).
6). The skip amount B is set to a value sufficiently larger than the integration amount b.

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

FIG. 6 shows an example of transition 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 over the reference voltage Vr (skip timing), the feedback correction coefficient FAF changes so as to change relatively greatly. While the increase / decrease operation is performed based on the quantities A and B,
In the period (integration period) from the time when the output voltage Vox of the oxygen sensor 46 changes over the reference voltage Vr to the time when it changes over the reference voltage Vr again (integration period), the integration amount is changed so as to change relatively gradually. The increase / decrease operation is performed based on a and b.

Here, when the actual air-fuel ratio and the theoretical air-fuel ratio do not tend to steadily deviate, the feedback correction coefficient FAF is around its reference value "1.0" and its vicinity. Will fluctuate with. Therefore, the average value FAFAV of the feedback correction coefficient FAF is approximately "1.
Is equal to 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 the solid difference in the injection characteristics of the fuel injection valve 20 or the 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 is
According to the deviation tendency, the value converges to a value different from “1.0”. Therefore, the reference value (= “1.0”) of this feedback correction coefficient FAF and its average value FAFA
Based on the deviation from V, the steady deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio can be monitored. In the process of 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 Processing] Next, the air-fuel ratio learning processing will be described with reference to the flowchart of FIG. The series of processes shown in this flowchart is repeatedly executed by the electronic control unit 50 at a predetermined cycle.

In this series of processes, first, it is judged whether or not the conditions for executing the air-fuel ratio learning process are satisfied (step S3302). The execution condition may be, for example, that the internal combustion engine 10 is in a complete warm-up state. Then, when the execution condition of the air-fuel ratio learning process is not satisfied (step S3302: NO), this series of processes is once ended.

On the other hand, when the execution condition of the air-fuel ratio learning process is satisfied (step S3302: YES), the feedback correction coefficient FAF is calculated according to the following arithmetic expression (2).
Is calculated (step S330).
4).

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 each skip amount A, B is performed. Is. That is, here, the feedback correction coefficient F when the output voltage Vox of the oxygen sensor 46 changes across the reference voltage Vr.
The arithmetic mean of the value FAFB of AF and the value of the feedback correction coefficient FAF when the output voltage Vox of the oxygen sensor 46 changes over the reference voltage Vr again is calculated as the average value FAFAV.

In this way, the feedback correction coefficient F
After the AF average value FAFAV is calculated, the current feedback correction coefficient FAF is stored as the value FAFB at the time of executing the previous skip processing in preparation for the next calculation processing (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).
Then, the average value FAF of the feedback correction coefficient FAF
When AV is less than the predetermined value α (step S3308:
YES), it is determined that the actual air-fuel ratio tends to deviate toward the rich side with respect to the theoretical air-fuel ratio, and the air-fuel ratio learning value KGi is learned so as to have a smaller value in order to compensate for this deviation tendency. . That is, the predetermined value γ is subtracted from the current air-fuel ratio learning value KGi, and the subtraction value (KG-γ) is set as the new air-fuel ratio learning value KGi (step S331).
4).

On the other hand, when the average value FAFAV of the feedback correction coefficient FAF is greater than or equal to the predetermined value β (step S
3310: NO), it is determined that the actual air-fuel ratio tends to deviate toward the lean side with respect to the theoretical air-fuel ratio, and learning is performed so that the air-fuel ratio learning value KGi becomes a larger value in order to compensate for this deviation tendency. To be done. That is, the current air-fuel ratio learning value KGi
Is added with a predetermined value γ, and the added value (KG + γ) is set as a new air-fuel ratio learning value KGi (step S3).
312). After the air-fuel ratio learning value KGi is updated in this step S3312 or the previous step S3314, this series of processing is temporarily terminated.

On the other hand, the feedback correction coefficient F
When the average value FAFAV of AF 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”, and the actual air-fuel ratio is the theoretical air-fuel ratio. It is judged that there is no tendency to deviate from the fuel ratio. Then, in this case, the series of processes is temporarily ended without updating the air-fuel ratio learning value KGi.

[5. Abnormality Determination Processing] Next, the abnormality determination processing will be described with reference to the flowchart of FIG. The series of processes shown in this flowchart is repeatedly executed by the electronic control unit 50 at a predetermined cycle.

In this series of processing, first, the air-fuel ratio correction amount F
AFKGi is calculated based on the following arithmetic expression (3) (step S500). Note that the subscript "i" indicates the corresponding relationship with each engine load region Ri, as with the air-fuel ratio learning value KGi.

FAFKGi ← FAF + KGi−2 (3) This air-fuel ratio correction amount FAFKGi is 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 each of these air-fuel ratio correction amounts FAFKGi. It shows the overall behavior with the air-fuel ratio learning value KGi that changes according to the steady deviation tendency of the fuel ratio. 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 FAFKG
i is, for example, as a deviation tendency between the actual air-fuel ratio and the stoichiometric air-fuel ratio, a negative value (air-fuel ratio correction amount when the actual air-fuel ratio shows a deviation toward the rich side of the theoretical air-fuel ratio, that is, a rich tendency. FAFKGi <0). On the other hand, as the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio, when the actual air-fuel ratio tends to deviate to the lean side from the theoretical air-fuel ratio, that is, when it shows the 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 match, that is, when there is no deviation between the respective air-fuel ratios, the reference value is “0”.

Since the air-fuel ratio learning value KGi is referred to when calculating the air-fuel ratio correction amount FAFKGi, the actual air-fuel ratio and the theoretical air-fuel ratio are different from the theoretical air-fuel ratio due to the fuel evaporation from the lubricating oil due to the abnormality of the fuel injection system or the fuel dilution. When a steady deviation tendency from the fuel ratio occurs, the air-fuel ratio correction amount FAFKGi changes according to the deviation tendency.

When 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, when there are few opportunities to satisfy the air-fuel ratio learning processing execution condition, the air-fuel ratio learning value KGi
Since the accuracy of is decreased, when considering the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio as a parameter for comprehensively evaluating,
The reliability of the air-fuel ratio correction amount FAFKGi may decrease. Therefore, when the deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio changes, the feedback correction coefficient FAF, which can change relatively quickly in response to the change, is also referred to when calculating the air-fuel ratio correction amount FAFKGi. I am trying.

In this way, the air-fuel ratio correction amount FAFKGi
Is calculated, 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, if any one of the following conditions (1) and (2) is satisfied, it is determined that the abnormality determination condition is satisfied. (1) The air-fuel ratio correction amount FAFKGi is the judgment value JMAX2.
A predetermined time has passed with the state above (> 0) (lean abnormality).

(2) The predetermined time has elapsed (rich abnormality) while the air-fuel ratio correction amount FAFKGi remains below the judgment value JMIN2 (<0). Here, the air-fuel ratio correction amount FAFKGi is determined by the determination value JMAX to determine whether or not the predetermined time has elapsed.
Based on that the counter value (duration counter value Cj) that is counted up at every predetermined time from the time when it becomes 2 or more or the time when it becomes the judgment value JMIN2 or less exceeds the predetermined value Cj1 (Cj> Cj1) Will be judged.

When it is determined that the abnormality determination condition is satisfied (steps S510 and S520: YE
S), it is determined that an abnormality has occurred in the fuel injection system (step S530). Then, this series of processing is once ended.

On the other hand, the air-fuel ratio correction amount FAFKGi is equal to the abnormality determination region RJ [JMIN2 <FAFKGi <JMAX.
2] (step S510: NO), it is not determined that there is an abnormality in this process, and the duration time counter value Cj is reset to “0” (S54).
0), this series of processing is once terminated.

If the air-fuel ratio adjustment 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 executed. It will be finished once. That is, in this case, although the air-fuel ratio correction amount FAFKGi shows an increasing tendency, this may be due to a temporary fluctuation, and an abnormality occurs because the reliability is still low with respect to this tendency. The determination that there is a change is put on hold.

[6. Prohibition Condition Judgment Process] Next, the prohibition condition judgment process will be described with reference to the flowchart of FIG. The series of processing shown in this flowchart is
It is repeatedly executed by the electronic control unit 50 at a predetermined cycle.

In this series of processing, first, it is judged whether or not a difference between the actual air-fuel ratio and the theoretical air-fuel ratio due to fuel dilution actually occurs (step S60).
0). More specifically, in this case, the degree of fuel dilution is large and the air-fuel ratio correction amount FAFKGi has increased by a predetermined amount or more as a deviation tendency between the actual air-fuel ratio and the stoichiometric air-fuel ratio on the side that compensates the rich tendency. It is determined whether or not. Specifically, when both of the following conditions (1) and (2) are satisfied, it is determined that the above situation exists.

(1) Fuel dilution occurrence flag XS is "ON"
Is set to. (2) The air-fuel ratio correction amount FAFKGi is equal to or less than the determination value JMIN1 (where JMIN2 <JMIN1 <0).

Here, the condition (2) is that the air-fuel ratio correction amount FA
FKGi is a predetermined amount (JMIN1) on the side that compensates for the rich tendency as a deviation tendency between the actual air-fuel ratio and the theoretical air-fuel ratio.
This is a condition for determining that the number is increasing.

Then, if it is determined that the above situation is present (step S600: YES), then the internal combustion engine 1
0 is operating in the engine low load region, specifically, the engine load region is the region R on the lowest load side among the regions Ri divided based on the size of the intake air amount.
It is determined whether or not it is 1 (step S610).

If it is determined that the internal combustion engine 10 is operating in the low engine load range (step S610:
(YES), the determination that there is an abnormality in the fuel injection system is prohibited. Specifically, the previous duration counter value Cj is reset to "0" (step S620).
That is, here, the continuation time counter value Cj is set so that a negative determination is always made in step S520 shown in FIG.
Is reset to "0", thereby prohibiting the determination that there is substantially an abnormality.

By the way, when such a prohibition process is executed, when the fuel dilution degree is large (the fuel dilution occurrence flag XS is "ON"), it is substantially determined that the rich abnormality is present. Will be banned. That is, when the fuel dilution occurrence flag XS is set to “ON”, the above [5. Even if the rich abnormality condition (2) in [Abnormality determination processing] is satisfied, the above condition (2) (FAFKGi ≦ JMIN1) is always satisfied, so that the determination of abnormality cannot be made 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 steps S620 and S610, similarly, this series of processing is once terminated. The apparatus according to the present embodiment, which is configured to diagnose the abnormality related to the fuel injection system in the manner described above, has the following effects.

(1) The fuel dilution degree of the entire 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 entire lubricating oil is large ( Fuel dilution occurrence flag XS = “O
N ”), and therefore, on the condition that the amount of fuel vaporized from the lubricating oil is increasing, a limitation is imposed on the determination that there is an abnormality in the fuel injection system. Specifically, it is prohibited. I chose Therefore, it becomes possible to surely suppress the erroneous diagnosis due to the fuel dilution of the lubricating oil in the abnormality diagnosis.

(2) In particular, when carrying out such prohibition,
Not only the degree of fuel dilution is large, but also the air-fuel ratio correction amount F
The execution condition is that AFKGi is increased by a predetermined amount or more on the side that compensates the rich tendency. Therefore, when the fuel evaporation amount due to the fuel dilution increases and the difference between the air-fuel ratios actually occurs due to the increase, the determination that there is an abnormality is prohibited. Therefore, for example, if the air-fuel ratio correction amount FAFKGi is designed to compensate for the lean tendency, in other words, if there is no risk of erroneous diagnosis due to a large fuel dilution level, the above prohibition is not made. Therefore, it becomes possible to avoid unnecessary prohibition of the determination that there is an abnormality.

(3) Also, under the condition that the fuel dilution degree increases, the history of the operation of the internal combustion engine 10, that is, the history of cold short trip is monitored, and the monitoring result is used as the dilution degree counter value C. I will refer to it when operating. Therefore, it becomes possible to relatively easily estimate the fuel dilution degree of the entire lubricating oil, which is generally difficult to directly detect.

(4) Further, when the engine is stopped, 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 the predetermined amount G.
It is determined that such a cold short trip has been made on the condition that it is equal to or lower than ASUML. Therefore, the determination can be made accurate, and the reliability of the history of the operation of the internal combustion engine 10 under the circumstances where the fuel dilution degree increases can be improved.

(5) Further, when such a cold short trip is made, the dilution degree counter value C is incremented, while the engine cooling water temperature THW and the predetermined temperature THWL are increased.
It is determined whether or not the fuel dilution degree is decreasing by comparison with the above, and when the fuel dilution degree is decreasing, the countdown is performed so that the dilution degree counter value C gradually decreases. ing. Therefore, whether the fuel dilution degree of the entire lubricating oil increases or decreases, it can be accurately estimated based on the dilution degree counter value C, and based on the same dilution degree counter value C. It becomes possible to appropriately prohibit the determination that there is an abnormality.

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

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

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

In this series of processing, first, the fuel dilution amount Δ per unit time is calculated based on the following arithmetic expression (4).
FD, that is, the amount of fuel newly mixed in the lubricating oil through the fuel injection performed during the time period T is calculated (step S700). Also, this fuel dilution amount ΔFD
Corresponds to the rate of increase 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 where f () is the fuel dilution amount generated by one fuel injection. Is a function for obtaining the fuel injection amount, and the fuel injection amount QINJ and the fuel injection timing AIN when the fuel injection is executed.
J and engine cooling water temperature THW are used as the parameters.
Further, “i” indicates how many times the fuel injection corresponds to the previous control cycle. For example, when the fuel injection is performed three times between the previous control cycle and the current control cycle, the arithmetic expression (4) can be expressed as the following expression (5).

ΔFD ← f (QINJ1, AINJ2, THW1) + f (QINJ2, AIN J2, THW2) + f (QINJ3, AINJ2, THW3) (5) This function f () is obtained in advance through experiments and the like. The
It is stored in the memory 52 of the electronic control unit 50 as a function map. The basic characteristics are as shown below.

The value of the function f () increases as the fuel injection amount QINJ increases. The function f () increases as the fuel injection timing AINJ is retarded.
The value of the function f () increases as the engine cooling water temperature THW decreases. The fuel injection amount QINJ, the fuel injection timing AINJ, and the engine cooling water temperature THW are selected as the parameters of the function f (). The reasons for doing so are as follows.

That is, the fuel dilution caused by the fuel injection is
This occurs when the fuel adhering to the cylinder inner peripheral surface 18 remains without being used for combustion. Therefore, the greater the amount of fuel adhered to the cylinder inner peripheral surface 18, the greater the degree of fuel dilution of the entire lubricating oil. Conceivable. Although it is usually difficult to directly detect the fuel adhesion amount on the cylinder inner peripheral surface 18, it is possible to accurately estimate and determine it by appropriately selecting a parameter having a correlation with the fuel adhesion amount. become able to.

Fuel injection amount QINJ, fuel injection timing A
INJ and the engine cooling water temperature THW are both representative examples of parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18.

For example, when the fuel injection amount QINJ increases, the fuel adhesion amount on the cylinder inner peripheral surface 18 naturally increases. Further, when fuel adheres to the cylinder inner peripheral surface 18, there is an upper limit value in 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 is increased, the thickness of such a fuel layer is less likely to reach its upper limit value, and more fuel can be adhered to the cylinder inner peripheral surface 18. Then, this fuel adhesion area, that is, the area of the cylinder inner peripheral surface 18 which is not covered by the piston 14 and is exposed to the combustion chamber 12 at the time of fuel injection is determined by the fuel injection timing AINJ, and if the intake stroke injection is assumed, Same fuel injection timing A
It becomes larger as INJ is set to the timing on the retard side. Therefore, 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 to the inner peripheral surface 18 of the cylinder is basically remarkable when the atomization of the injected fuel is not promoted and the particle size is large. Further, the degree of atomization largely depends on the temperature of the combustion chamber 12 and the fuel, if 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, the atomization of the fuel is not promoted as the engine cooling water temperature THW is lower, so that the fuel adhesion amount on the cylinder inner peripheral surface 18 increases.

In the device according to this embodiment, the fuel injection amount QINJ and the fuel injection timing AI are taken into consideration in consideration of these points.
The NJ and the engine cooling water temperature THW are selected as parameters having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18.

When the fuel dilution amount ΔFD is calculated in this manner, the fuel evaporation amount ΔFV per unit time, that is, the lubricating oil during the time period T, is calculated based on the following equation (6). The amount of fuel evaporated from the whole is calculated (step S710). The fuel evaporation amount ΔFV corresponds to the rate of decrease in the fuel dilution degree when the fuel dilution due to the 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 is the engine starting water temperature TH.
WST, integrated value of fuel injection amount after engine start QINJSUM
Is the parameter. Incidentally, the engine starting water temperature THWST is 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 starting the engine is for estimating the subsequent temperature increase amount of the lubricating oil. It 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
It is obtained in advance through experiments or the like and is stored in the memory 52 of the electronic control unit 50 as a function map. The basic characteristics are as shown below.

The value of g () increases as the engine start water temperature THWST increases. The value of g () increases as the integrated fuel injection amount QINJSUM after engine start increases. When the dilution amount ΔFD and the fuel evaporation amount ΔFV are calculated, the fuel dilution degree FDSUM is then calculated based on the following calculation formula (7) (step S720).

FDSUM ← FDSUM + ΔFD−ΔFV (7) As shown in the above equation (7), here, the increasing speed ΔFD of the fuel dilution degree FDSUM and the decreasing speed Δ thereof.
The current fuel dilution degree FDSUM is updated based on the FV. Then, the updated value is the new fuel dilution degree FDS.
It is learned as UM and is stored and held in the memory 52 of the electronic control unit 50.

Next, the fuel dilution degree FDSUM is compared with the determination value FDSUMH (step S730).
Here, the fuel dilution degree FDSUM is the determination value FDSUMH
When the above is the case (step S730: YES), the degree of fuel dilution of the entire lubricating oil is large, and it is determined that if the fuel dilution proceeds any further, its adverse effect will become so large that it can no longer be ignored. Then, on condition that such a determination is made, the fuel dilution occurrence flag X
S is set to "ON" (step S740).

On the other hand, the fuel dilution degree FDSUM is the judgment value F
If it is less than DSUMH (step S730: N
O), then the fuel dilution degree FDSUM and the judgment value FDSUM
L (<FDSUMH) is compared (step S73).
5). Here, the fuel dilution degree FDSUM is the determination value FDS
If it is less than or equal to UML (step S735: YE
S), the degree of fuel dilution of the entire lubricating oil is small, so even if fuel dilution occurs temporarily due to fuel injection and the degree of fuel dilution of the entire lubricating oil progresses, the adverse effect on the internal combustion engine 10 due to this is almost ignored. It is judged that it is possible. Then, on 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 a negative determination is made in any of the previous steps S730 and S735, this series of processing is temporarily terminated.

In the prohibition condition determination process (see FIG. 10), the fuel dilution occurrence flag XS operated through the fuel dilution degree calculation process is used to execute step S600.
The condition (1) is determined. This point is the same as the device according to the first embodiment.

According to the apparatus according to the present embodiment, which is configured to diagnose the abnormality related to the fuel injection system in the manner described above, the apparatus described in (1) and (2) shown in the first embodiment is In addition, the following effects can be obtained.

(6) The fuel dilution degree FDSUM based on the parameter having a correlation with the fuel adhesion amount on the cylinder inner peripheral surface 18.
The increase rate (fuel dilution amount per unit time) ΔFD of Δ is calculated for each predetermined time period T. And
The current fuel dilution degree FDSUM is updated based on the calculated increase rate ΔFD, and this is learned as a new fuel dilution degree FDSUM.
Therefore, this can be accurately and accurately estimated according to the increase in the fuel dilution degree FDSUM, and the effects described in the above (1) and (2) can be more effectively exhibited. Like

(7) Further, in such learning, not only the increasing speed (fuel dilution amount per unit time) ΔFD of the fuel dilution degree FDSUM, but also the decreasing speed (fuel evaporation amount per unit time) ΔFV, This is calculated based on the engine start water temperature THWST and the lubricating oil temperature estimated from the fuel injection amount integrated value QINJSUM after engine start. Then, these increasing speeds ΔF
The fuel dilution degree FDSUM is updated and learned based on both D and the decrease rate ΔFV.
Therefore, it becomes possible to more accurately estimate 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, particularly, the fuel injection amount,
Since the fuel injection timing, the engine temperature, or the like having a stronger correlation with the fuel adhesion amount is selected, 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 prohibition condition determination process (FIG. 10),
The determination method for determining whether or not the deviation between the actual air-fuel ratio and the theoretical air-fuel ratio due to fuel dilution actually occurs is different from that of the first embodiment.

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

Specifically, step S shown in FIG.
The condition (1) in the processing of 600 is changed as follows. (1) | KG5-KG1 |> JKG Here, as described above, "KG5" is the air-fuel ratio learning value KGi in the region R5 on the highest load side, and "KG1".
Is the air-fuel ratio learning value KGi in the region R1 on the lowest load side.
Is. Further, "JKG" is a determination value for determining that the degree of deviation between the air-fuel ratio learning values KG1, 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. Therefore, the steady deviation tendency between the actual air-fuel ratio and the target air-fuel ratio is reflected in the air-fuel ratio learning value KGi. Like

When the engine load is low, the fuel injection valve 20
Since the fuel injection amount from the engine is relatively small, when the fuel is evaporated from the lubricating oil, the ratio of this fuel evaporation amount to the fuel amount supplied to the internal combustion engine 10 is compared with that during engine high load operation. And grow bigger. Therefore, the air-fuel ratio learning value KG1 at low engine load is easily affected by the amount of evaporated fuel,
Comparing with the air-fuel ratio learning value KG5 during engine high load operation,
Differences can be seen in the deviation tendency.

Therefore, by using the conditional expression (1) to monitor the degree of deviation between the two air-fuel ratio learning values KG1 and KG5, it is accurately determined that the fuel evaporation amount from the lubricating oil is increasing. It becomes possible to prohibit the determination that there is an abnormality. As a result, also in the present 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 is
The configuration and a part of the control procedure can be changed and implemented 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. XS is set to "ON" or each air-fuel ratio learning value KG in the engine load region
The degree of deviation between 1 and KG5 is large (| KG5-KG1
Only |> JKG) may be set as the prohibition condition.

In each of the above-described embodiments, the determination that there is an abnormality is prohibited, but instead of such prohibition, for example, step S51 in FIG.
At 0, the determination value JMIN2 may be changed to a smaller negative value, the predetermined value Cj1 in step S520 may be increased, or the condition for determining an abnormality may be changed to make such determination difficult. .

In the third embodiment, the fact that the degree of deviation between the value in the engine high load range and the value in the engine low load range is large is evaluated by these differences, but it is evaluated by, for example, their ratio. You can also do it. Alternatively, for example, the air-fuel ratio learning values KG5 to K in the load regions R3 to R5 on the high load side.
The air-fuel ratio learning value in the low load range R1 is estimated by extrapolation based on G3, and the estimated value and the actual air-fuel ratio learning value KG1.
The degree of deviation may be evaluated based on the comparison with.

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, so that the lubricating oil increases as the average temperature of the entire lubricating oil increases. It is determined that the amount of fuel evaporated from the whole has risen 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 integrated value of the fuel injection amount after the engine is started (only if homogeneous combustion is selected as the combustion mode It is also possible to substitute the integrated value of air amount)
The temperature rise amount is estimated based on. Then, the fuel evaporation amount can be calculated based on the lubricating oil temperature calculated as the sum of the initial value and the temperature increase amount.

In the first embodiment, the engine starting water temperature T
HWST 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 GASUML is a determination condition when it is determined that the current engine operation corresponds to a cold short trip. . This judgment condition is changed, for example, the engine operating time from the engine start to the stop is measured, 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 the above.

In the first embodiment, the predetermined amount GAS which is compared with the intake air amount integrated value GASUM after the engine is started.
The UML may be variably set according to the engine starting water temperature THWST. Specifically, the engine starting water temperature TH
It is desirable to set this so that the predetermined amount GASUML decreases as WST increases.

In the first embodiment, the dilution degree counter value C is incremented by a predetermined amount α. Here, the degree of deviation between the engine starting water temperature THWST and the predetermined temperature THWL (for example, the deviation (THWL-THWST)).
Since the fuel dilution amount tends to increase as the value of (), etc.) increases, it is also effective to increase the predetermined amount α as the degree of deviation increases. Further, the intake air amount integrated value GASUM after starting the engine and the predetermined amount GASUML
Degree of deviation from (for example, the difference (GASUML-GASU
Similarly, for M)), the predetermined amount α may be increased as the degree of deviation is larger. Further, a configuration in which the predetermined amount α is variably set based on both of these deviation degrees is also effective.

In the first embodiment, the dilution degree counter value C is counted down by a predetermined amount β. Here, as the deviation degree between the engine cooling water temperature THW and the predetermined temperature THWH (for example, the deviation (THW-THWH) or the like) is larger, the fuel evaporation amount tends to increase, so the predetermined amount β is set to the deviation degree. You may make it increase so that it is large.

In the first embodiment and the modifications thereof described above, in determining whether or not the current engine operation corresponds to a cold short trip, the intake air amount integrated value GASUM after engine start and Corresponding predetermined amount GASUML
However, instead of the intake air amount integrated value GASUM after the engine is started, the fuel injection integrated value after the engine is started can be adopted.

In the above embodiments, the air-fuel ratio correction amount FA
When calculating FKGi, the feedback correction coefficient FAF and the air-fuel ratio learning value K are calculated as shown in the above equation (3).
Although both Gi are referred to, only the air-fuel ratio learning value KGi may be referred to, for example.

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. it can.

In each of the above embodiments, the fuel dilution degree is estimated on the assumption that the fuel dilution and the evaporation of the fuel 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 higher than when the engine is stopped, but regarding fuel evaporation, it actually occurs even during such engine stop. There is. For this reason,
For example, the engine stop time is measured, the lubricating oil temperature at the engine start (or the engine stop) is estimated, and the fuel evaporation amount during the engine stop is estimated based on the engine stop time and the lubricating oil temperature. You may do it. Then, when estimating the fuel dilution degree, if the fuel evaporation amount while the engine is stopped is also taken into consideration, the fuel dilution degree can be estimated more accurately.

The combustion heat generated in each fuel injection is
In addition to the intake air amount and the fuel injection amount, it also changes depending on the air-fuel ratio at the time of fuel injection, the ignition timing, and the like. Therefore, in the first embodiment, the intake air amount integrated value GASU after the engine is started.
It is also effective to consider this point when calculating M, and in the second embodiment, when calculating the fuel injection amount integrated value QINJSUM after engine start. Specifically, for each of these values GASUM, QINJSUM,
A method of performing weighting by the air-fuel ratio, ignition timing, and the like and performing integration thereof is also effective in increasing the accuracy in estimating the combustion heat quantity and further the lubricating oil temperature.

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 engine starting. For example, this may be configured so that a sensor that directly detects the lubricating oil temperature is provided, and it may be modified to perform the various controls described above based on the detection result. In this case, it is desirable to detect the temperature of the lubricating oil in a temperature state having a high correlation with the average temperature of the entire lubricating oil, such as the lubricating oil temperature in the oil pan 74.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an abnormality diagnosis device and an internal combustion engine to which the abnormality diagnosis device is applied.

FIG. 2 is a flowchart showing a processing procedure of operation monitoring processing.

FIG. 3 is a flowchart showing a processing procedure of operation monitoring processing.

FIG. 4 is a timing chart showing an operation mode and the like of a fuel dilution occurrence flag.

FIG. 5 is a flowchart showing a processing procedure of fuel injection amount calculation processing.

FIG. 6 is a timing chart showing an example of how the feedback correction coefficient changes.

FIG. 7 is a flowchart showing a processing procedure of air-fuel ratio feedback processing.

FIG. 8 is a flowchart showing a processing procedure of air-fuel ratio learning processing.

FIG. 9 is a flowchart showing a processing procedure of abnormality determination processing.

FIG. 10 is a flowchart showing a processing procedure of prohibition condition determination processing.

FIG. 11 is a flowchart showing a processing procedure of a fuel dilution degree calculation processing.

[Explanation of symbols]

10 ... Internal combustion engine, 11 ... Intake passage, 12 ... Combustion chamber, 13
… Exhaust passage, 14… Piston, 16… Head cover, 1
7 ... Cylinder, 18 ... Cylinder inner peripheral surface, 19 ... Crankcase,
20 ... Fuel injection valve, 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, limiting means), 52 ... Memory, 60 ... Accelerator pedal, 70 ... Lubrication system, 72 ... Lubricating oil supply device, 74 ... Oil pan, 80 ... Blow-by gas reduction Device, 82 ... Communication passage, 84 ... Blow-by gas passage, 86 ... Flow control valve.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 45/00 F02D 45/00 314Z 340 340D 340G 364 364Q 366 366H (72) Inventor Koji Honda Honda, Aichi Prefecture Toyota Town No. 1 Toyota Motor Co., Ltd. F term (reference) 3G084 BA09 BA11 CA01 CA02 DA27 DA29 EA11 EB08 EB18 EB20 FA07 FA10 FA20 FA29 FA33 FA36 3G301 HA01 HA04 JB09 JB10 KA01 KA02 LA01 LB01 MA01 MA11 MA18 NA07 NA30 ND30 NC02 ND28 ND45 PA01Z PA11Z PE01Z PE08Z PF16Z

Claims (16)

[Claims] 1. An in-cylinder injection internal combustion engine having a determination means for determining an abnormality of a fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control obtained based on a deviation tendency between an actual air-fuel ratio and a target air-fuel ratio. In an engine abnormality diagnosis device, an estimating unit that estimates the fuel dilution degree of the entire lubricating oil that is used for lubrication of the internal combustion engine, and the estimation unit of the determining unit on the condition that the estimated fuel dilution degree is large. An abnormality diagnosing device for a cylinder injection internal combustion engine, comprising: a limiting unit that limits an operation of determining that there is an abnormality. 2. The limiting means is provided on the side for compensating for the tendency that the actual air-fuel ratio deviates to the rich side from the target air-fuel ratio as the deviation tendency of the air-fuel ratio correction amount and the estimated fuel dilution degree is large. The abnormality diagnosis device for a cylinder injection internal combustion engine according to claim 1, wherein the determination operation is limited on the condition that the amount of increase is equal to or more than a predetermined amount. 3. The abnormality diagnosing device for a cylinder injection type internal combustion engine according to claim 1, wherein the estimating means estimates the fuel dilution degree based on the operation history of the internal combustion engine. 4. The estimation means monitors the operation of the internal combustion engine under a situation where the fuel dilution degree increases, and estimates the fuel dilution degree based on the monitoring history. Cylinder injection type internal combustion engine abnormality diagnosis device. 5. The estimating means estimates the total amount of heat of combustion generated in the cylinder between the engine start and the engine stop based on the engine operating state, and the engine temperature at the engine start is equal to or lower than a predetermined temperature. The abnormality diagnosis of the cylinder injection type internal combustion engine according to claim 4, wherein when the estimated total combustion heat amount is equal to or less than a predetermined amount, it is determined that the internal combustion engine is operated under the situation where the fuel dilution degree increases. apparatus. 6. The estimating means determines that the total combustion heat quantity is less than or equal to a predetermined amount when the intake air amount integrated value or the fuel injection amount integrated value from engine start to engine stop is less than or equal to a predetermined value. The in-cylinder injection type internal combustion engine abnormality diagnosis device according to claim 5. 7. The estimating means judges whether or not the fuel dilution degree is decreasing based on the temperature of the lubricating oil or a parameter having a correlation with the temperature, and the fuel dilution degree is increased. The magnitude of the counter value that is counted up when a history indicating that the internal combustion engine has been operated occurs under the circumstances, and is gradually counted down when it is determined that the situation in which the fuel dilution degree decreases The abnormality diagnosis device for a direct injection internal combustion engine according to claim 4, wherein the fuel dilution degree is estimated based on the above. 8. The estimating means calculates an increasing speed of the fuel dilution degree on the basis of a parameter having a correlation with an amount of fuel adhering to the inner peripheral surface of the cylinder by fuel injection, and based on the calculated increasing speed. The abnormality diagnosis device for a direct injection internal combustion engine according to claim 1, wherein the fuel dilution degree is sequentially updated and learned to estimate the fuel dilution degree. 9. The estimating means, when calculating the increasing rate of the fuel dilution degree, correlates at least one of the fuel injection amount, the fuel injection timing, and the engine temperature with the fuel adhesion amount on the inner peripheral surface of the cylinder. 9. Selection as a parameter
An in-cylinder injection type internal combustion engine abnormality diagnosis apparatus. 10. The estimating means further estimates the amount of fuel evaporated from the entire lubricating oil based on the temperature of the lubricating oil or a parameter having a correlation with the temperature, and the fuel based on the estimated fuel evaporation amount. A method of estimating the fuel dilution degree by calculating a decrease rate of the dilution degree, and sequentially updating and learning the fuel dilution degree based on the calculated decrease rate and the calculated increase rate. Item 8. An abnormality diagnosis device for a cylinder injection internal combustion engine according to item 8 or 9. 11. An in-cylinder injection internal combustion engine having a determination means for determining an abnormality of a fuel injection system based on an air-fuel ratio correction amount of air-fuel ratio feedback control obtained based on a deviation tendency between an actual air-fuel ratio and a target air-fuel ratio. In an engine abnormality diagnosis device, an air-fuel ratio learning value is calculated for each engine load region divided into a plurality of values in order to compensate for a steady deviation tendency between the actual air-fuel ratio and the target air-fuel ratio, and is calculated for each engine load region. For each air-fuel ratio learning value, provided with a limiting means for limiting the determination operation for determining that the determination means is abnormal, on the condition that the degree of deviation between the value in the engine high load range and the value in the engine low load range is large. An in-cylinder injection type internal combustion engine abnormality diagnosing device. 12. The limiting means increases the amount of deviation by a predetermined amount or more on the side that compensates for the tendency that the actual air-fuel ratio deviates to the rich side from the target air-fuel ratio as the deviation tendency. 12. The abnormality diagnosis device for a cylinder injection internal combustion engine according to claim 11, wherein the determination operation is restricted under the condition that the above condition is satisfied. 13. The abnormality diagnosing apparatus for a cylinder injection internal combustion engine according to claim 1, wherein the limiting means applies the limitation on condition that the engine is under a low load. 14. The abnormality diagnosing device for a cylinder injection type internal combustion engine according to claim 1, wherein the limiting means prohibits the abnormality determination by the determining means. 15. The in-cylinder injection according to claim 1, wherein the limiting means changes a condition for the determination means to determine that there is an abnormality so that it is difficult to determine that the abnormality is present. Type internal combustion engine abnormality diagnosis device. 16. The cylinder according to claim 1, wherein the limiting means limits the determination operation of the determining means for determining 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 system for internal combustion engine.