JP2012087632A - Abnormality diagnostic device for fuel supply system of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abnormality diagnostic device for a fuel supply system of an internal combustion engine capable of diagnosing abnormality in an early stage in the case it is generated in a fuel supply system by restraining drastic deviation of an alcohol concentration learning value from the original value and avoiding unnecessary limitation of execution period of an abnormality diagnostic process of the fuel supply system due to prolongation of a concentration learning process.SOLUTION: A period from having the inflow accumulation amount after determination of oil supply reaching an amount of starting supply of a fuel of a fuel tank 1 to a delivery pipe 4 to having the fuel in the delivery pipe 4 reach an amount of being substituted to a fuel after oil supply is defined as a concentration learning period so that the concentration learning process is executed only in that period. An abnormality diagnostic process for the fuel supply system is executed based on the deviation tendency of the real air-fuel ratio and the theoretical air-fuel ratio in the period excluding the concentration learning period.

Description

  The present invention relates to a fuel supply system abnormality diagnosis device for an internal combustion engine that can use a fuel containing alcohol at an arbitrary ratio to gasoline.

  In general, in an internal combustion engine, air-fuel ratio feedback control is performed to correct the fuel injection amount of the fuel injection valve so that the actual air-fuel ratio of the internal combustion engine matches the stoichiometric air-fuel ratio. If any abnormality occurs in the fuel supply system of the internal combustion engine under such air-fuel ratio feedback control, it becomes difficult to appropriately supply the required amount of fuel to the internal combustion engine. As a result, in the air-fuel ratio feedback control, the fuel injection amount is corrected so as to compensate for this, and therefore it is possible to perform abnormality diagnosis processing of the fuel supply system based on the excessive increase in the correction degree. .

  In recent years, attention has been focused on an internal combustion engine that can use a fuel containing alcohol in an arbitrary ratio with respect to gasoline. In such an internal combustion engine, since the theoretical air-fuel ratio varies depending on the alcohol concentration contained in the fuel, it is required to control the fuel injection amount in accordance with the alcohol concentration. In view of this, a control device for an internal combustion engine is known in which the concentration learning value indicating the concentration of alcohol contained in the fuel is updated after refueling. For example, in the control device described in Patent Document 1, if it is determined that the fuel tank has been refueled, the difference between the actual air-fuel ratio and the theoretical air-fuel ratio that occurs after the refueling is caused by a change in the alcohol concentration of the fuel. In the period until the actual air-fuel ratio converges to the stoichiometric air-fuel ratio, a concentration learning process for updating the alcohol concentration learning value is executed based on the deviation tendency. The fuel injection amount is corrected in accordance with the alcohol concentration learning value updated in this way.

JP 2008-51063 A

  Here, in the fuel supply system abnormality diagnosis device that executes the abnormality diagnosis process of the fuel supply system of the internal combustion engine, when the concentration learning process as described above is executed together, there is a concern that the alcohol concentration learned value may be mislearned. The This is because when the learning error of the alcohol concentration learning value occurs, the stoichiometric air-fuel ratio grasped from the learning value and the actual stoichiometric air-fuel ratio deviate. This is because the value may be different from the value, which may cause inconvenience such as erroneous determination that an abnormality has occurred in the fuel supply system.

  Such mislearning of the alcohol concentration learning value occurs, for example, when the execution period of the concentration learning process is not set appropriately. Specifically, as described in Patent Document 1, when the concentration learning process is executed until the actual air-fuel ratio converges to the stoichiometric air-fuel ratio after refueling, the concentration learning process is being executed. For example, when a change in the output value of the air-fuel ratio sensor due to an abnormality in the fuel supply system occurs, the execution period of this concentration learning process may become unnecessarily long. As a result, the alcohol concentration learning value is updated as a value that also compensates for the deviation between the actual air-fuel ratio and the stoichiometric air-fuel ratio due to an abnormality in the fuel supply system. This is different from its original value of compensating for the deviation from the theoretical air-fuel ratio. Further, when the execution period of the concentration learning process is prolonged as described above, the execution period of the abnormality diagnosis process is limited by that amount, and thus an abnormality in the fuel supply system cannot be detected at an appropriate time.

  The present invention has been made in view of such circumstances, and the object thereof is to suppress the alcohol concentration learning value from greatly deviating from the original value and to increase the fuel supply system by extending the concentration learning process. A fuel supply system abnormality diagnosis device for an internal combustion engine capable of early diagnosis when an abnormality has occurred in the fuel supply system while avoiding an unnecessary restriction on the execution period of the abnormality diagnosis process It is to provide.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 includes a fuel supply system that supplies alcohol fuel in a fuel tank to a delivery pipe through a supply passage from a fuel delivery mechanism and supplies the fuel to an internal combustion engine through a fuel injection valve connected to the delivery pipe. Air-fuel ratio feedback means for performing air-fuel ratio feedback control for correcting the fuel injection amount of the fuel injection valve so that the actual air-fuel ratio of the internal combustion engine matches the stoichiometric air-fuel ratio according to the alcohol concentration of the fuel; Learning means for executing a concentration learning process for updating an alcohol concentration learning value for correcting a fuel injection amount based on a deviation tendency between a required actual air-fuel ratio and a theoretical air-fuel ratio, and a fuel supply system based on the deviation tendency In the fuel supply system abnormality diagnosis device for an internal combustion engine having abnormality diagnosis means for executing the abnormality diagnosis process, the tank is not refueled. Refueling determining means for determining that the fuel has been supplied, and calculating means for calculating an integrated amount of inflow of fuel flowing into the delivery pipe after determining that refueling has been performed. The concentration learning period is a period from when the accumulated amount of inflow reaches the amount at which fuel in the fuel tank starts to be supplied to the delivery pipe until it reaches the amount at which the fuel in the delivery pipe is replaced with fuel after refueling. The concentration learning process is executed only during the same period, and the abnormality diagnosis means executes the abnormality diagnosis process based on the deviation tendency in a period excluding the concentration learning period. .

  In the above configuration, the accumulated inflow amount of the fuel flowing into the delivery pipe after refueling is calculated, and the execution period of the concentration learning process is set based on the inflow accumulated amount. That is, when the accumulated inflow amount reaches the amount at which the fuel after refueling starts to be supplied to the delivery pipe, the concentration learning process is started, while the fuel at the delivery pipe is replaced with the fuel after refueling. The time when it is reached is the end time of the density learning process. For this reason, the concentration learning process can be executed with an appropriate period in which the change in the air-fuel ratio due to the change in the alcohol concentration of the fuel is expected to occur, even if the air-fuel ratio has changed due to an abnormality in the fuel supply system. The influence can be kept to a minimum, and a situation in which the concentration learning process is unnecessarily prolonged can be avoided. As a result, it is possible to prevent the alcohol concentration learning value from greatly deviating from the original value due to the lengthening of the concentration learning processing, and the execution period of the abnormality diagnosis processing of the fuel supply system is limited. If the fuel supply system has an abnormality, this can be diagnosed early.

  Here, the inflow integrated amount of fuel flowing into the delivery pipe can be calculated by selectively integrating either one of the fuel pumping amount and the fuel injection amount of the fuel pumping mechanism. That is, when all the fuel pumped from the fuel pumping mechanism flows into the delivery pipe, the inflow integrated amount can be calculated by integrating the fuel pumping amount, while the fuel discharged from the delivery pipe is the fuel. When the amount is the same as the injection amount, the inflow integrated amount can be calculated by integrating the fuel injection amount. Further, in the fuel supply system, if the state in which all the fuel pumped from the fuel pumping mechanism flows in and the state in which the fuel discharged from the delivery pipe is equal to the fuel injection amount are appropriately switched, that state It is also possible to switch the target to be sequentially accumulated between the fuel pumping amount and the fuel injection amount.

  The “fuel supply system abnormality” includes not only the abnormality of the fuel injection valve such as the fuel injection characteristic deviating greatly from the original characteristic, but also the abnormality of the fuel supply piping such as the delivery pipe, as well as the fuel injection amount. This includes abnormalities in the intake air amount sensor used for setting and the air-fuel ratio sensor that detects the actual air-fuel ratio.

  According to a second aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the first aspect, the abnormality diagnosis unit is configured to start the concentration learning process after determining that refueling has been performed. This period is included as an execution period of the abnormality diagnosis process.

  Even when refueling is performed, the fuel before refueling is supplied from the fuel injection valve to the internal combustion engine until the concentration learning process is started. For the fuel before refueling, since the concentration learning value has already been updated according to the alcohol concentration changed by the previous refueling, the updated alcohol is used in the period until the concentration learning process described above is started. The fuel supply is performed with the fuel injection amount appropriately corrected based on the concentration learning value. Therefore, even after refueling, the abnormality diagnosis process can be executed during the period before the concentration learning process is executed, and the abnormality diagnosis process is executed during the same period to increase the frequency of executing the abnormality diagnosis process. This makes it possible to detect an abnormality in the fuel supply system at an early stage.

  According to a third aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the first or second aspect, the learning means is provided on the condition that the integrated inflow amount is equal to or larger than a volume of the supply passage. The gist of the present invention is to provide a start time determination means for determining that the time when the condition is satisfied is the start time of the concentration learning process.

  Even when the fuel tank is refueled, the fuel after refueling does not immediately flow into the delivery pipe, but first the fuel before refueling remaining in the supply passage flows into the delivery pipe. . Then, after all the fuel before refueling remaining in the supply passage flows into the delivery pipe, the fuel after refueling flows into the delivery pipe. Therefore, as described above, when the accumulated inflow amount exceeds the volume of the supply passage, it is determined that the concentration learning process is started, and the concentration learning process is started at an appropriate time by starting the process. Will be able to start.

  According to a fourth aspect of the present invention, in the internal combustion engine fuel supply system abnormality diagnosis device according to any one of the first to third aspects, the learning means is configured such that the integrated inflow amount is equal to the volume of the supply passage and the volume of the supply passage. The gist of the invention is that it comprises an end time determination means for determining that the concentration learning process is ended when the condition is satisfied, when the amount exceeds a predetermined amount determined by the volume of the delivery pipe.

  The accumulated inflow amount required until the fuel in the delivery pipe is replaced with the fuel after refueling after refueling can be uniquely determined by the volume of the supply passage and the volume of the delivery pipe. Therefore, as described above, when the accumulated inflow amount is equal to or greater than a predetermined amount determined by the volume of the supply passage and the volume of the delivery pipe, it is determined that the concentration learning process is finished and the process is terminated. The same concentration learning process can be ended at an appropriate time.

  According to a fifth aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the fourth aspect, the end timing determining means sets the integrated inflow amount to ΣQdel, the volume of the supply passage to Va, and the delivery pipe. The gist of this is to determine when the following condition is satisfied as the end time of the concentration learning process, where Vb is Vb.

ΣQdel ≧ Va + Vb · α
α: 2.5 ≦ α ≦ 3.5

Here, when the fuel after refueling starts to flow into the delivery pipe, the inventor refuels the fuel in the delivery pipe if the subsequent inflow integrated amount reaches 2.5 to 3.5 times the volume of the delivery pipe. The knowledge that it was replaced with later fuel was obtained by experiments. Therefore, as in the above configuration, the concentration learning is performed when the inflow integrated amount reaches the value obtained by adding the volume of the supply passage and the value of α times the volume of the delivery pipe (2.5 ≦ α ≦ 3.5). The process can be ended by determining that it is the end time of the process.

  According to a sixth aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to any one of the first to fifth aspects, the fuel pumping mechanism increases the pressure of the fuel supplied to the delivery pipe. The gist is that at least switching between a state and a lower pressure state than this state is possible.

  Since the theoretical air-fuel ratio of alcohol is smaller than the theoretical air-fuel ratio of gasoline, the higher the alcohol concentration of fuel, the greater the fuel injection amount required to ensure the same engine output. Therefore, in the fuel supply system of the internal combustion engine that can use such a mixed fuel of alcohol and gasoline, the fuel injection amount is controlled over a wide range compared to the fuel supply system of the internal combustion engine that uses only gasoline as fuel. Need arises. In particular, when the required value of the engine output increases in a situation where fuel with a high alcohol concentration is used, it is impossible to inject an amount of fuel commensurate with it. On the other hand, it is possible to cope with this by increasing the fuel injection pressure. In this case, however, the fuel injection time when the fuel injection amount is small is shortened, so that it is necessary to increase the control accuracy of the fuel injection time. . The fuel pressure feed mechanism configured as described above can switch the pressure of the fuel supplied to the delivery pipe between at least a low pressure state and a high pressure state, and accordingly, the injection pressure of the fuel injection valve can be set in two stages. . Therefore, the fuel injection amount can be appropriately controlled over a wide range.

  According to a seventh aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the sixth aspect, the fuel supply system includes a return path for returning surplus fuel in the delivery pipe to the fuel tank, and the return. A pressure regulating valve that is provided in a passage and opens when the fuel pressure of the delivery pipe is equal to or higher than a predetermined valve opening pressure, and the fuel pressure feeding mechanism supplies the fuel in the fuel tank to the delivery pipe through the supply passage. A fuel pump for supplying the fuel to the fuel tank, a relief passage connected to the downstream side of the fuel pump in the supply passage and returning the fuel in the supply passage to the fuel tank, and a communication state between the relief passage and the supply passage. A switching valve for switching, and opening the switching valve to return the fuel in the supply passage to the fuel tank through the relief passage. While setting the fuel pressure of the variable pipe to the low pressure state, the delivery valve is closed, the pressure regulating valve is opened, and surplus fuel in the delivery pipe is returned to the fuel tank through the return passage. The calculation means calculates the inflow integrated amount based on the fuel injection amount of the fuel injection valve when the switching valve is opened, while closing the switching valve. The gist is to calculate the inflow integrated amount based on the fuel pumping amount of the fuel pump at the time of valve operation.

  In the above configuration, when the switching valve is open and the fuel is returned to the fuel tank through the relief passage, a part of the fuel pumped from the fuel pump flows into the delivery pipe and enters the delivery pipe. All of the fuel that flows in is supplied from the fuel injection valve to the internal combustion engine. On the other hand, when surplus fuel in the delivery pipe is returned to the fuel tank through the return passage when the switching valve is closed, all the fuel pumped from the fuel pump flows into the delivery pipe and the fuel that has flowed into the delivery pipe. A part of the fuel is supplied from the fuel injection valve to the internal combustion engine. Therefore, as in the above configuration, when the switching valve is opened, the inflow integrated amount is calculated based on the fuel injection amount of the fuel injection valve, while when the switching valve is closed, the integrated inflow amount is calculated based on the fuel pumping amount of the fuel pump. By doing so, the integrated amount of inflow into the delivery pipe can be calculated appropriately. Thereby, the execution period of the density learning process can be set appropriately.

  According to an eighth aspect of the present invention, in the fuel supply system abnormality diagnosis device for an internal combustion engine according to the seventh aspect, the fuel pumping mechanism is configured to perform the operation until the concentration learning period elapses after it is determined that refueling has been performed. The gist is to maintain the fuel pressure of the delivery pipe at the high pressure state.

  In this configuration, after determining that refueling has been performed, the fuel pressure in the delivery pipe is set to a high pressure state, and excess fuel in the delivery pipe is returned to the fuel tank through the return passage. It is possible to set the time required until the fuel is replaced, in other words, the execution period of the concentration learning process, so that the output of the air-fuel ratio sensor is based on the abnormality in the fuel supply system during the execution of the concentration learning process. Opportunities for the value to change can be further reduced, which can further suppress the erroneous learning of the alcohol concentration learning value. Furthermore, since the execution period of the abnormality diagnosis process can be set longer, an abnormality in the fuel supply system can be diagnosed earlier.

1 is a configuration diagram of a fuel supply system abnormality diagnosis apparatus according to a first embodiment that embodies a fuel supply system abnormality diagnosis apparatus for an internal combustion engine according to the present invention and a fuel supply system that is a diagnosis target thereof. The flowchart which shows the process sequence about the period setting process for setting the execution period of the density | concentration learning process in the embodiment. 6 is a flowchart showing a processing procedure of density learning processing in the embodiment. The flowchart which shows the process sequence of the air fuel ratio learning process in the embodiment. The flowchart which shows the process sequence of the abnormality diagnosis process in the embodiment. The timing chart which shows the setting aspect of each execution period of a density | concentration learning process and an abnormality diagnosis process, and transition of an air fuel ratio learning value and a density | concentration learning value. The block diagram of the fuel supply system abnormality diagnostic apparatus of 2nd Embodiment and the fuel supply system which is the diagnostic object. The flowchart which shows the process sequence about the period setting process for setting the execution period of the density | concentration learning process in the embodiment. The flowchart which shows the process sequence about the period setting process for setting the execution period of the density | concentration learning process in 3rd Embodiment.

(First embodiment)
A first embodiment that embodies a fuel supply system abnormality diagnosis device (hereinafter referred to as a diagnosis device) for an internal combustion engine according to the present invention will be described below with reference to FIGS.

  FIG. 1 shows a fuel supply system abnormality diagnosing device and a fuel supply system of an internal combustion engine that is the object of diagnosis. This internal combustion engine is a V-type multi-cylinder internal combustion engine that can use fuel containing alcohol (specifically, ethanol) at an arbitrary ratio to gasoline.

  The fuel tank 1 is provided with an electric fuel pump 2 that pumps fuel stored therein and a fuel level gauge 21 that detects the remaining amount of fuel. In addition, a relief passage 6 for returning a part of the fuel in the supply passage 3 to the fuel tank 1 is connected to the supply passage 3 for transferring the fuel discharged from the fuel pump 2 to the pair of delivery pipes 4. A low-pressure pressure regulator 8 that opens when the fuel pressure in the supply passage 3 and the relief passage 6 is equal to or higher than a predetermined low-pressure PL is provided at the end of the relief passage 6 that is open to the fuel tank 1. . In addition, an electromagnetically driven switching valve 7 for switching the communication state between the relief passage 6 and the supply passage 3 is provided in the relief passage 6 upstream of the low-pressure pressure regulator 8.

  The supply passage 3 is connected to a fuel inlet 4 a formed on one side of the delivery pipe 4. A plurality of fuel injection valves 5 for injecting fuel and supplying it to each cylinder of the internal combustion engine are connected to these delivery pipes 4 respectively. A return passage 10 is connected to the other end 4 b of the delivery pipe 4 to return the surplus fuel from the delivery pipe 4 to the fuel tank 1. The return passage 10 is provided with a high pressure regulator 9 that opens when the fuel pressure in the delivery pipe 4 is equal to or higher than a predetermined high pressure PH. The high pressure pressure regulator 9 functions as a pressure regulating valve that regulates the fuel pressure of the delivery pipe 4, in other words, the fuel injection pressure of the fuel injection valve 5 to a predetermined high pressure PH. The predetermined low pressure PL and the predetermined high pressure PH described above are used to appropriately control the fuel injection amount over a wide range from when the fuel used is 100% gasoline to when the alcohol concentration is the highest concentration (for example, 85%). Thus, an appropriate fuel injection pressure is set.

  The fuel pump 2, the relief passage 6, the switching valve 7, and the low-pressure pressure regulator 8 have a function as a fuel pumping mechanism 30 that pumps the alcohol fuel in the fuel tank 1 to the delivery pipe 4 through the supply passage 3. .

  In addition to the fuel level gauge 21 described above, the electronic control device 20 that controls the fuel injection valve 5 and the fuel pumping mechanism 30 collectively includes an air flow meter 22 that detects the intake air amount, and a rotation speed sensor that detects the engine rotation speed. 23, an air-fuel ratio sensor 24 provided in the exhaust passage of the internal combustion engine and outputting a signal corresponding to the air-fuel ratio of the internal combustion engine is connected. The electronic control unit 20 includes a calculation unit (CPU) and a plurality of memories 20a that store and hold various control programs, calculation maps, data calculated when the control is executed, and the like. A part of the memory 20a functions as a backup memory that retains the stored information even when the engine is stopped by being supplied with power by a battery (not shown). The electronic control unit 20 takes in the detection signals of these sensors, and executes open / close control of the switching valve 7 in addition to air-fuel ratio feedback control (fuel injection control) based on the detection results.

  In this open / close control, for example, when the internal combustion engine is in a high-load high-rotation state and the alcohol concentration of the fuel is high, the required fuel injection amount becomes relatively large, so the switching valve 7 is closed. Then, the fuel pressure of the delivery pipe 4 is adjusted to a predetermined high pressure PH. That is, the pressure of the fuel supplied to the delivery pipe 4 by the fuel pumping mechanism 30 becomes a high pressure state. On the other hand, when the internal combustion engine is in a low-load low-rotation state and the alcohol concentration of the fuel is low, the required fuel injection amount becomes relatively small. Therefore, the switching valve 7 is opened and the delivery pipe 4 is The fuel pressure is adjusted to a predetermined low pressure PL. That is, the pressure of the fuel supplied to the delivery pipe 4 by the fuel pumping mechanism 30 becomes a low pressure state.

  In the fuel injection control, the basic fuel is based on the case where gasoline is injected based on the intake air amount detected by the air flow meter 22, that is, the engine load and the engine rotational speed detected by the rotational speed sensor 23. An injection amount QBASE is calculated. The basic fuel injection amount QBASE is corrected by a feedback correction value FAF, an air-fuel ratio learning value KG, which will be described later, and a concentration learning value EG corresponding to the concentration of alcohol contained in the fuel, and a final fuel injection amount QFIN is calculated. (See equation (1)).

QFIN ← QBASE · {(1.0 + EG / 100) · (1.0+ (FAF + KG) / 100)} (1)
FAF: Feedback correction value (%)
KG: Air-fuel ratio learning value (%)
EG: Concentration learning value (%)

Here, the feedback correction value FAF is set to 0% as a reference value, and is appropriately set according to the degree of deviation between the air-fuel ratio AF and the theoretical air-fuel ratio SAF during the execution of the air-fuel ratio feedback control. That is, if the air-fuel ratio AF is richer than the stoichiometric air-fuel ratio SAF, the feedback correction value FAF is set to a small value according to the richness, and if the air-fuel ratio AF is leaner than the stoichiometric air-fuel ratio, A large value is set according to the degree of lean. Here, the stoichiometric air-fuel ratio SAF is a weight ratio of the intake air to the fuel when the fuel is completely burned by oxygen contained in the intake air.

  Further, when the fuel supply system, for example, the fuel injection valve 5 or the air flow meter 22 has its injection characteristic or detection characteristic changed with time or there is an individual difference, a theory is given during execution of the air-fuel ratio feedback control. A steady deviation of the air-fuel ratio AF with respect to the air-fuel ratio SAF occurs. In order to correct such a steady bias, the air / fuel ratio learning process for updating the air / fuel ratio learning value KG described above is executed by the electronic control unit 20 based on the feedback correction value FAF. As a result, when a deviation tendency in which the air-fuel ratio AF is steadily biased to the rich side or the lean side from the stoichiometric air-fuel ratio SAF can be compensated by the air-fuel ratio learning value KG, feedback is possible. The correction value FAF can be returned to the vicinity of 0% which is the reference value.

  Further, since the theoretical air-fuel ratio (about 9.0) of alcohol, that is, ethanol is smaller than the theoretical air-fuel ratio (about 14.7) of gasoline, the theoretical air-fuel ratio SAF of the fuel decreases as the alcohol concentration of the fuel increases. . Therefore, if the fuel injection amount of the fuel injection valve 5 is the same, the air-fuel ratio AF tends to lean toward the lean side as the alcohol concentration increases, and the air-fuel ratio AF tends to lean toward the rich side as the alcohol concentration decreases. Show. Therefore, when the alcohol concentration of the fuel injected from the fuel injection valve 5 changes as the fuel having a different alcohol concentration from the fuel used before refueling is supplied to the fuel tank 1, the air-fuel ratio AF. Tends to be biased toward the rich side or lean side. Therefore, based on the feedback correction value FAF, the electronic control unit 20 executes a concentration learning process for updating the concentration learning value EG for compensating for the deviation tendency between the air-fuel ratio AF and the theoretical air-fuel ratio SAF.

  Here, if any abnormality occurs in the fuel supply system of the internal combustion engine under such air-fuel ratio feedback control, the fuel injection characteristics change greatly, so that the required amount of fuel can be appropriately injected and supplied to the internal combustion engine. It becomes difficult. Therefore, the electronic control unit 20 executes an abnormality diagnosis process of the fuel supply system based on the air-fuel ratio learning value KG indicating the tendency of deviation between the air-fuel ratio AF and the theoretical air-fuel ratio SAF. The abnormality of the fuel supply system is not only the abnormality of the fuel injection valve 5 such as the fuel injection characteristic greatly deviating from the original characteristic, but also the abnormality of the fuel supply piping such as the supply passage 3 and the delivery pipe 4, etc. The abnormality of the air flow meter 22 and the air-fuel ratio sensor 24 used when setting the fuel injection amount QBASE is also included.

  Incidentally, as described above, since both the concentration learning process and the abnormality diagnosis process are executed based on the deviation tendency between the air-fuel ratio AF and the stoichiometric air-fuel ratio SAF, there is a concern about erroneous learning of the concentration learning value EG. This is because if the false learning of the concentration learning value EG occurs, the theoretical air-fuel ratio SAF grasped from the concentration learning value EG deviates from the actual theoretical air-fuel ratio SAF, so the degree of correction of the fuel injection amount in the air-fuel ratio feedback control Is different from the original value, and the fuel injection amount QFIN cannot be calculated appropriately, and this may cause a problem of erroneous determination that an abnormality has occurred in the fuel supply system.

  Such erroneous learning of the density learning value EG occurs, for example, when the execution period of the density learning process is not set appropriately. In other words, when the concentration learning process is executed when the air-fuel ratio AF is changing due to an abnormality in the fuel supply system, the concentration learning value EG is equal to the air-fuel ratio AF and the theoretical sky due to the abnormality in the fuel supply system. The value is also updated as a value that compensates for the deviation from the fuel ratio SAF, which is significantly different from the original value that compensates for the deviation between the air-fuel ratio AF and the stoichiometric air-fuel ratio SAF due to a change in alcohol concentration. Further, if the execution period of the concentration learning process is set inappropriately long, the execution period of the abnormality diagnosis process is limited by that amount, so that an abnormality of the fuel supply system cannot be detected at an appropriate time.

  Therefore, in the present embodiment, the execution period of the density learning process and the abnormality diagnosis process is set by executing the process shown in FIG. A series of processes shown in the figure is repeatedly executed with a predetermined cycle by the electronic control unit 20 after the internal combustion engine is started.

  When this process is started, first, it is determined whether or not the refueling flag F is “OFF” (step S101). In this determination, the determination is made by reading the refueling flag F stored in the memory 20a of the electronic control unit 20.

  If it is determined that the refueling flag F is “OFF” (step S101: YES), it is then determined whether refueling has been performed (step S102). Specifically, when it is determined that the fuel in the fuel tank 1 has increased by a predetermined amount or more based on the output value of the fuel level gauge 21, it is determined that refueling has been performed. The processing in this step corresponds to the processing executed by the fuel supply determination unit.

  Then, when it is determined that the fuel is not supplied (step S102: NO), it can be determined that the alcohol concentration of the fuel is not changed and it is not necessary to execute the concentration learning process. Is terminated. Thereafter, air-fuel ratio feedback control, air-fuel ratio learning control, and abnormality diagnosis processing are executed based on the output value of the air-fuel ratio sensor 24, respectively.

  On the other hand, when it is determined that refueling has been performed (step S102: YES), the refueling flag F is set to “ON” (step S103), and information on the refueling flag F is stored in the memory 20a. .

  Subsequently, the switching valve 7 is closed (step S104), whereby the fuel pressure PD of the delivery pipe 4 is set to a high pressure state. That is, when the switching valve 7 is closed, all the fuel pressure-fed from the fuel pump 2 flows into the delivery pipe 4. When the fuel pressure PD of the delivery pipe 4 reaches a predetermined high pressure PH (PD ≧ PH), the high pressure pressure regulator 9 is opened, and surplus fuel in the delivery pipe 4 is returned to the fuel tank 1 through the return passage 10. As a result, the fuel pressure PD of the delivery pipe 4 is adjusted to a predetermined high pressure PH and set to a high pressure state.

  When the switching valve 7 is in the closed state in this way, as described above, all the fuel pressure-fed from the fuel pump 2 flows into the delivery pipe 4, and then the inflow integration of the fuel into the delivery pipe 4 after refueling is continued. The amount ΣQdel is calculated by the following equation (2) using the fuel pumping amount (pump discharge amount Qp) of the fuel pump 2 (step S105).

Inflow integrated amount ΣQdel ← Previous inflow integrated amount ΣQdel + pump discharge amount Qp (2)

Note that the previous inflow integrated amount ΣQdel in the above equation (2) is the inflow integrated amount ΣQdel calculated at the time of the previous execution of the processing of step S105, and the pump discharge amount Qp is the current processing from the previous processing execution time. This is the amount of fuel pumped from the fuel pump 2 by the time of execution. The processing in step S105 corresponds to processing executed by the calculation unit.

  By the way, when refueling is performed, first the fuel before refueling remaining in the supply passage 3 first flows into the delivery pipe 4 and the fuel before refueling is supplied from the fuel injection valve 5 to the internal combustion engine. The After all the fuel before refueling remaining in the supply passage 3 flows into the delivery pipe 4, the fuel after refueling flows into the delivery pipe 4 and is replaced with the fuel before refueling in the delivery pipe 4. Be started.

Therefore, first, it is determined whether or not the calculated inflow integrated amount ΣQdel satisfies the relationship of the following equation (3) (step S106).

Inflow integrated amount ΣQdel ≧ supply passage volume Va (3)

If an affirmative determination is made in this process (step S106: YES), it can be determined that the fuel after refueling flows into the delivery pipe 4. If it is determined that refueling has been performed in the determination process of step S102 (step S102: YES), and if a positive determination is made for the first time in the determination process of step S106 (step S106: YES), concentration learning is performed. It is determined that it is time to start processing. The determination process in step S106 corresponds to a process executed by the start time determination unit.

Subsequently, it is determined whether or not the inflow integrated amount ΣQdel satisfies the relationship of the following equation (4) (step S107).

Inflow integrated amount ΣQdel ≧ supply passage volume Va + delivery pipe volume Vb × 3 (4)

Here, according to the inventor's experiment, when the fuel after refueling starts to be supplied to the delivery pipe 4, the subsequent inflow integrated amount ΣQdel is 2.5 to 3.5 times the volume Vb of the delivery pipe 4. In addition, the knowledge that the fuel in the delivery pipe 4 is almost replaced by the fuel after refueling has been obtained. In particular, the fuel of the delivery pipe 4 can be suitably obtained by using three times the volume Vb of the delivery pipe 4 as an index. It has been found that the replacement of can be determined. Therefore, when a negative determination is made in the determination process of step S107 (step S107: NO), that is, when the inflow integrated amount ΣQdel satisfies the relationship of the following equation (5), It can be determined that it is a period in which replacement of fuel with fuel before refueling is being executed.

Inflow integrated amount ΣQdel <supply passage volume Va + delivery pipe volume Vb × 3 (5)

As the fuel in the delivery pipe 4 is replaced, the alcohol concentration of the fuel supplied from the fuel injection valve 5 to the internal combustion engine gradually changes, so that the air-fuel ratio AF changes due to the alcohol concentration change of the fuel. Become. Therefore, when a negative determination is made in the determination process of step S107 (step S107: NO), a concentration learning process for updating the alcohol concentration learning value EG based on the change in the air-fuel ratio AF is executed (step S108). This process is temporarily terminated. Details of the density learning process will be described later.

  Further, when the process from step S101 is executed again during the execution of the concentration learning process, since the refueling flag F is set to “ON”, a negative determination is made in the determination process of step S101 ( Step S101: NO) Subsequently, the process of step S105 is executed. Then, when the determination process of the next step S106 is executed, since the fuel after refueling has already flowed into the delivery pipe 4, a positive determination is made (step S106: YES), and then the determination process of step S107 is executed. Is done.

  On the other hand, if an affirmative determination is made that the above equation (4) is satisfied in the determination process of step S107 (step S107: YES), it is determined that all the fuel in the delivery pipe 4 has been replaced with the fuel after refueling. can do. Therefore, if the concentration learning process is being executed and if the determination is affirmative for the first time in the determination process of step S107 (step S107: YES), it is determined that it is the end time of the concentration learning process. . The determination process in step S107 corresponds to a process executed by the end time determination unit.

  When the concentration learning process is thus completed, the fuel supply flag F is set to “OFF” (step S109). If the change in the air-fuel ratio AF occurs after the concentration learning process is completed, it is determined that the change in the air-fuel ratio AF is caused by a factor other than the alcohol concentration of the fuel, for example, an abnormality in the fuel supply system. I can.

  By the way, when a negative determination is made in the determination process of step S106 (step S106: NO), that is, when the inflow integrated amount ΣQdel satisfies the relationship of the following equation (6), it remains in the supply passage 3. It can be determined that the fuel before refueling is still flowing into the delivery pipe 4.

Inflow integrated amount ΣQdel <supply passage volume Va (6)

For the fuel before refueling, since the concentration learning value EG has already been updated according to the alcohol concentration changed by the previous refueling, the fuel injection amount QFIN is calculated based on the already updated concentration learning value EG. Is done. Therefore, if a change in the air-fuel ratio AF occurs in this state, it can be determined that this change in the air-fuel ratio AF is due to factors other than changes in the alcohol concentration of the fuel, for example, an abnormality in the fuel supply system.

  Therefore, when a negative determination is made by the determination process of step S106 (step S106: NO) or when an affirmative determination is made by the determination process of step S107 (step S107: YES), the air-fuel ratio learning process is performed. When executed (step S110), an abnormality diagnosis process (step S111) is executed, and this process ends. Details of the air-fuel ratio learning process and the abnormality diagnosis process will be described later.

Next, with reference to FIG. 3, the processing procedure of the density learning process executed in step S108 described above will be described.
In this process, first, it is determined whether or not an update condition for the density learning value EG is satisfied (step S201). Specifically, it is determined by the following equation (7) whether or not the absolute value of the feedback correction value FAF exceeds the determination value α.

Absolute value of feedback correction value FAF | FAF |> determination value α (7)

As the determination value α, an appropriate value that can be determined that the change in the air-fuel ratio AF is caused by the change in the alcohol concentration of the fuel is set in advance, and is stored in the memory 20a of the electronic control unit 20.

  Here, when the alcohol concentration of the fuel increases with refueling, the air-fuel ratio AF is biased toward the lean side. Therefore, the feedback correction value FAF (%) is corrected to increase the fuel injection amount QFIN through the air-fuel ratio feedback control. Is set (FAF> 0). On the other hand, when the alcohol concentration of the fuel decreases with refueling, the air-fuel ratio AF is biased to the rich side. Therefore, the feedback correction value FAF (%) is negative to reduce the fuel injection amount QFIN through the air-fuel ratio feedback control. A value is set (FAF <0).

  Therefore, when it is determined in the determination process that the update condition of the density learning value EG is satisfied (step S201: YES), the density learning value EG is updated (step S202), and this process ends. . Specifically, when the feedback correction value FAF is a positive value, the concentration learning value EG is increased by a constant value A (EG ← EG + A). On the other hand, when the feedback correction value FAF is a negative value, the concentration learning value EG is decreased by a constant value A (EG ← EG−A).

  In this way, the concentration learning value EG is updated to a concentration learning value EG corresponding to the alcohol concentration of the fuel after refueling during the execution of the concentration learning process by increasing or decreasing by a constant value every control cycle. Is done.

  On the other hand, when it is determined in the above-described determination process that the update condition of the concentration learning value EG is not satisfied (step S201: NO), the air-fuel ratio AF and the theoretical sky are determined even during the execution period of the concentration learning process. It can be determined that the degree of deviation from the fuel ratio SAF is small. This occurs when the alcohol concentration of the fuel after refueling is the same as the alcohol concentration of the fuel before refueling. Accordingly, in this case, the present process is terminated without updating the density learning value EG.

Next, with reference to FIG. 4, the process procedure of the air-fuel ratio learning process executed in step S110 described above will be described.
In this process, first, it is determined whether or not an update condition for the air-fuel ratio learning value KG is satisfied (step S301). Specifically, whether or not the absolute value of the feedback correction value FAF exceeds the determination value β is determined by the following equation (8).

Absolute value of feedback correction value FAF | FAF |> determination value β (8)

As the determination value β, an appropriate value for determining that a steady bias has occurred in the feedback correction value FAF is set in advance and is stored in the memory 20a of the electronic control unit 20.

  If it is determined in this determination process that the update condition for the air-fuel ratio learned value KG is satisfied (step S301: YES), the air-fuel ratio learned value KG is updated (step S302). Specifically, when the feedback correction value FAF (%) is a positive value (FAF> 0), the air-fuel ratio learning value KG is increased by a constant value B (KG ← KG + B). On the other hand, when the feedback correction value FAF is a negative value (FAF <0), the air-fuel ratio learning value KG is decreased by a constant value B (KG ← KG−B).

  On the other hand, when it is determined in the determination process described above that the update condition of the air-fuel ratio learning value KG is not satisfied (step S301: NO), it is determined that the feedback correction value FAF is close to the reference value of 0%. Therefore, the present process is terminated without updating the air-fuel ratio learned value KG.

Next, with reference to FIG. 5, the processing procedure of the abnormality diagnosis process executed in step S111 described above will be described.
When this process is started, it is determined whether or not the absolute value of the air-fuel ratio learning value KG updated by the above-described air-fuel ratio learning process exceeds the determination value γ by the following equation (9) (step S401). ).

Absolute value of air-fuel ratio learning value KG | KG |> judgment value γ (9)

The determination value γ is set in advance to an appropriate value with which it can be determined that the air-fuel ratio learning value KG is excessively large or small due to an abnormality in the fuel supply system, It is stored in the memory 20a of the electronic control unit 20.

  If an affirmative determination is made in the determination process described above (step S401: YES), it can be determined that an abnormality has occurred in the fuel supply system, so an abnormality determination is made (step S402). This process is terminated.

On the other hand, when a negative determination is made in the determination process (step S401: NO), it can be determined that no abnormality has occurred in the fuel supply system, and the present process is terminated.
Next, with reference to FIG. 6, the setting aspect of each execution period of the concentration learning process and the abnormality diagnosis process after refueling will be described. In the present embodiment, as described above, since the air-fuel ratio learning process and the abnormality diagnosis process are executed subsequently, these execution periods are the same.

  If it is determined that refueling has been performed at time t1 after the start of the internal combustion engine, the refueling flag F is set to “ON”. Then, between time t1 and time t2, the fuel before refueling remaining in the supply passage 3 first flows into the delivery pipe 4, so that the concentration learning process is stopped, while the air-fuel ratio learning process and Abnormality diagnosis processing is executed.

  When it is determined based on the integrated inflow amount ΣQdel that the fuel after refueling has started to be supplied to the delivery pipe 4 at time t2, this time t2 is determined as the start time of the concentration learning process, and the concentration learning process is started. The Then, when the feedback correction value FAF changes during the execution period of the concentration learning process and the absolute value of the feedback correction value FAF exceeds the determination value α (| FAF |> α), the concentration learning value EG is updated accordingly. The

  When it is determined at time t3 that the fuel in the delivery pipe 4 has been replaced with fuel after refueling based on the integrated inflow amount ΣQdel, this time t3 is determined as the end time of the concentration learning process, and the concentration learning process ends. Is done. Note that the period from time t2 to time t3 corresponds to the concentration learning period.

  As the concentration learning process ends, the air-fuel ratio learning process and the abnormality diagnosis process are started. When the feedback correction value FAF changes at time t4, which is the execution period of these air-fuel ratio learning process and abnormality diagnosis process, and the absolute value of the feedback correction value FAF exceeds the determination value β (| FAF |> β), Accordingly, the air-fuel ratio learning value KG is updated. Further, when the absolute value of the air-fuel ratio learning value KG exceeds the determination value γ (| KG |> γ) at time t5, an abnormality determination is made and the abnormality flag is set to “ON”.

According to 1st Embodiment described above, there can exist the following effects.
(1) The accumulated inflow amount ΣQdel of the fuel flowing into the delivery pipe 4 after refueling is calculated, and the execution period of the concentration learning process is set by the inflow accumulated amount ΣQdel (steps S106 and S107). That is, when the accumulated inflow amount ΣQdel reaches the amount at which the fuel after refueling begins to be supplied to the delivery pipe 4, the concentration learning process is started (step S106: YES), while the fuel in the delivery pipe 4 is The time when the amount replaced with the fuel after refueling is reached (step S107: YES) is the end time of the concentration learning process. For this reason, the concentration learning process can be executed with an appropriate period in which the change in the air-fuel ratio AF due to the change in the alcohol concentration of the fuel is expected to occur. However, the influence can be kept to a minimum, and a situation in which the concentration learning process is unnecessarily prolonged can be avoided. As a result, it is possible to prevent the alcohol concentration learning value EG from greatly deviating from the original value due to such prolonged concentration learning processing, and to limit the execution period of the abnormality diagnosis processing of the fuel supply system This can be avoided, and if an abnormality occurs in the fuel supply system, it can be diagnosed early.

  (2) Since the abnormality diagnosis process is executed in a period after refueling and before the concentration learning process is executed, the frequency of executing the abnormality diagnosis process can be increased, and an abnormality in the fuel supply system can be detected early. Can be detected.

  (3) It is determined that the concentration learning process is started when the accumulated inflow amount ΣQdel is equal to or greater than the volume Va of the supply passage 3 (step S106: YES), and the concentration learning process is started. Processing can be started at an appropriate time.

  (4) When the accumulated inflow amount ΣQdel is greater than or equal to a predetermined amount determined by the volume Va of the supply passage 3 and the volume Vb of the delivery pipe 4 (step S107: YES), it is determined that the concentration learning processing end time is reached. Since the process is terminated, the same concentration learning process can be terminated at an appropriate time.

  (5) After the fuel after refueling starts to flow into the delivery pipe 4, when the inflow integrated amount ΣQdel reaches three times the volume of the delivery pipe 4 (step S107: YES), the concentration learning process ends. Since the determination is made and the process is terminated, the density learning process can be terminated at an appropriate time.

  (6) Since the inflow integrated amount ΣQdel is calculated based on the fuel pumping amount (pump discharge amount) Qp of the fuel pump 2 (step S105), the inflow integrated amount ΣQdel can be appropriately calculated. Thereby, the execution period of the density learning process can be set appropriately.

  (7) In the internal combustion engine in the present embodiment, it is necessary to control the fuel injection amount over a wide range as compared with the fuel supply system of the internal combustion engine that uses only gasoline as fuel. In particular, when the required value of the engine output increases in a situation where fuel with a high alcohol concentration is used, it is impossible to inject an amount of fuel commensurate with it. On the other hand, it is possible to cope with this by increasing the fuel injection pressure. In this case, however, the fuel injection time when the fuel injection amount is small is shortened, so that it is necessary to increase the control accuracy of the fuel injection time. . In the present embodiment, the pressure of the fuel supplied to the delivery pipe 4 can be switched between the low pressure state and the high pressure state by switching the opening and closing of the switching valve 7, so that the injection pressure of the fuel injection valve 5 is also adjusted accordingly. Two stages can be set. Therefore, the fuel injection amount can be appropriately controlled over a wide range.

  (8) After determining that the fuel has been supplied, the switching valve 7 is closed (step S104), so that the surplus fuel in the delivery pipe 4 is returned to the fuel tank 1 through the return passage 10, so that the fuel in the delivery pipe 4 It is possible to set the time required until the fuel is replaced with the fuel after refueling, in other words, the execution period of the concentration learning process. Therefore, in the execution period of the concentration learning process, the opportunity for the output value of the air-fuel ratio sensor 24 to change based on the abnormality of the fuel supply system can be further reduced, and thus the concentration learning value is erroneously learned. It becomes possible to suppress. Furthermore, since the execution period of the abnormality diagnosis process can be set longer, an abnormality in the fuel supply system can be diagnosed earlier.

(Second Embodiment)
Next, with reference to FIG. 7 and FIG. 8, the second embodiment that embodies the fuel supply system abnormality diagnosis device for an internal combustion engine according to the present invention is different from the first embodiment. The explanation will be focused on. In addition, about the same structure as the said 1st Embodiment, detailed description is abbreviate | omitted by attaching | subjecting the same code | symbol.

  As shown in FIG. 7, the fuel pumping mechanism 40 in this embodiment is not provided with the switching valve 7 in the relief passage 6, and surplus fuel is supplied from the delivery pipe 4 to the fuel tank 1 in the delivery pipe 4. The return passage 10 for returning is not provided.

  The fuel pump 41 of the fuel pumping mechanism 40 of the present embodiment is configured to be able to switch the pressure of the fuel supplied to the delivery pipe 4 between a low pressure state and a high pressure state. Specifically, the low pressure state is adjusted to a predetermined low pressure PL that is the valve opening pressure of the low pressure pressure regulator 8 in the first embodiment described above. On the other hand, the high pressure state is adjusted to a predetermined high pressure PH that is the valve opening pressure of the high pressure regulator 9 in the first embodiment. Note that the pressure regulator 42 in the embodiment is set to open when the fuel pressure in the relief passage 6 exceeds a predetermined high pressure PH.

  In the present embodiment, the process shown in FIG. 8 is executed instead of the process shown in FIG. 2 executed in the first embodiment described above. Note that the processes shown in FIGS. 3 to 4 are executed in the same manner in this embodiment.

When the process shown in FIG. 8 is started, the same processes as those shown in steps S101 to S103 in FIG. 2 are sequentially executed from step S501 to step S503.
Here, in this embodiment, the fuel discharged from the delivery pipe 4 is the same amount as the fuel injection amount. Therefore, the integrated flow amount ΣQdel of fuel into the delivery pipe 4 after refueling is calculated by the following equation (10) using the fuel injection amount Qinj of the fuel injection valve 5 (step S504).

Inflow integrated amount ΣQdel ← Previous inflow integrated amount ΣQdel + fuel injection amount Qinj (10)

Note that the previous inflow integrated amount ΣQdel in the above equation (10) is the inflow integrated amount ΣQdel calculated during the previous execution of the processing in step S504, and the fuel injection amount Qinj is the current processing from the previous processing execution time. This is the amount of fuel injected from the fuel injection valve 5 by the time of execution. The processing in step S504 corresponds to processing executed by the calculation unit.

  When the inflow integrated amount ΣQdel is calculated in this way, in the following steps S505 to S510, the processes shown in steps S106 to S111 of FIG.

According to 2nd Embodiment demonstrated above, in addition to the effect shown to said (1)-(5), (7), there can exist the following effects.
(9) Since the inflow integrated amount ΣQdel is calculated based on the fuel injection amount Qinj of the fuel pump 2 (step S504), the inflow integrated amount ΣQdel can be appropriately calculated. Thereby, the execution period of the density learning process can be set appropriately.

(Third embodiment)
Next, a third embodiment in which the fuel supply system abnormality diagnosis device for an internal combustion engine according to the present invention is embodied will be described with reference to FIG.

In this embodiment, each process shown in FIG. 9 is executed instead of a part of the process shown in FIG. 2 executed in the first embodiment.
That is, when the process of step S103 of FIG. 2 is completed, as shown in FIG. 8, it is determined whether or not the closing condition of the switching valve 7 is satisfied (step S601). Specifically, when it is determined that the internal combustion engine is not in idle operation, it is determined that the valve closing condition is satisfied.

  If it is determined that the closing condition of the switching valve 7 is satisfied (step S601: YES), the switching valve 7 is closed (step S602). When the switching valve 7 is closed, all of the fuel pressure-fed from the fuel pump 2 flows into the delivery pipe 4, so the inflow integrated amount ΣQdel is calculated by the following equation (11) (step S603). This equation is the same as the above equation (2) in the first embodiment.

Inflow integrated amount ΣQdel ← Previous inflow integrated amount ΣQdel + pump discharge amount Qp (11)

On the other hand, when the internal combustion engine is idling and it is determined that the closing condition of the switching valve 7 is not satisfied (step S601: NO), the switching valve 7 is opened (step S604). . When the switching valve 7 is opened, part of the fuel pumped from the fuel pump 2 flows into the delivery pipe 4 and all the fuel that flows into the delivery pipe 4 is supplied from the fuel injection valve 5 to the internal combustion engine. The Accordingly, the integrated inflow amount ΣQdel is calculated by the following equation (12) (step S605). This equation is the same as the above equation (10) in the second embodiment.

Inflow integrated amount ΣQdel ← Previous inflow integrated amount ΣQdel + fuel injection amount Qinj (12)

Thus, when the inflow integrated amount ΣQdel is calculated in step S603 or step S605, the process proceeds to step S106 shown in FIG. 2, and the subsequent processes are sequentially executed. In addition, each process of said step S603 and step S605 is equivalent to the process performed by a calculation means.

According to 3rd Embodiment described above, in addition to the effect shown to said (1)-(5), (7), (8), there can exist the following effects.
(10) Calculation of the integrated inflow amount ΣQdel based on the fuel pumping amount (pump discharge amount) Qp of the fuel pump 2 and the integrated inflow amount ΣQdel based on the fuel injection amount Qinj of the fuel pump 2 according to the open / close state of the switching valve 7 Therefore, the inflow integrated amount ΣQdel can be appropriately calculated. Thereby, the execution period of the density learning process can be set appropriately.

(Other embodiments)
Note that the fuel supply system abnormality diagnosis device for an internal combustion engine according to the present invention is not limited to the configuration exemplified in each of the above-described embodiments, and for example, the following embodiments in which those embodiments are appropriately changed Can also be implemented.

  -In 3rd Embodiment mentioned above, although the example which sets that the internal combustion engine was not at the time of idle driving | operation was shown as a valve closing condition of the switching valve 7 (step S601), it is not restricted to this. . For example, the valve closing condition may be that the internal combustion engine is not in idle operation and the air-fuel ratio sensor 24 is activated.

  In each of the above embodiments, it is determined that the concentration learning processing end time is when the accumulated inflow amount ΣQdel reaches three times the volume of the delivery pipe 4 after the fuel after refueling starts to flow into the delivery pipe 4. Although the example which performs is shown (step S107, step S506), about the setting method of an end time, it is not restricted to this example. For example, it is possible to adopt a mode in which it is determined that the end time is when the accumulated inflow amount ΣQdel reaches 3.5 times the volume of the delivery pipe 4 after the fuel after refueling starts to flow into the delivery pipe 4. . In other words, if the integrated inflow amount ΣQdel can be determined to have reached the amount at which the fuel in the delivery pipe 4 is replaced with the fuel after refueling, it depends on the volume of the supply passage 3 and the volume of the delivery pipe 4 that are the determination conditions. A predetermined amount can be set as appropriate. However, in order to suppress the execution period of the abnormality diagnosis process from being unnecessarily limited, it is desirable to appropriately set the end time so as to prevent the concentration learning period from being unduly prolonged. Even in this case, the effects shown in the above (1) to (4) and (6) to (10) can be achieved.

  In each of the above embodiments, whether or not the absolute value of the feedback correction value FAF exceeds the determination value β (| FAF |> β) in the determination processing as to whether or not the update condition of the air-fuel ratio learning value KG is satisfied. Although an example of determination is shown (step S301), the determination condition is not limited to this example. For example, in addition to the determination condition of the feedback correction value FAF, the determination condition is that the change in the engine speed and the intake air amount is small and the operation condition of the internal combustion engine is stable. The fuel ratio learning value KG may be updated.

  In the second embodiment, an example is shown in which the integrated inflow amount ΣQdel is calculated from the fuel injection amount Qinj (step S504). However, in the same embodiment, when the fuel pressure of the delivery pipe 4 is set to a low pressure state, the pressure regulator 42 that opens when a pressure higher than a predetermined high pressure PH is applied is in a closed state, so that the fuel pump 41 All the fuel pumped from is supplied to the delivery pipe 4. Therefore, when the fuel pressure of the delivery pipe 4 is set to the low pressure state as described above, the inflow integrated amount ΣQdel may be calculated from the pump discharge amount Qp as shown in the process of step S105. That is, in this case, the state in which all the fuel pumped from the fuel pumping mechanism 40 flows (low pressure state) and the state in which the fuel discharged from the delivery pipe 4 becomes the same amount as the fuel injection amount (low pressure state and high pressure). Therefore, it is only necessary to switch the target to be sequentially accumulated between the pump discharge amount Qp and the fuel injection amount Qinj in accordance with the state. Even in this case, the above-described effects can be achieved.

  In the second embodiment, the example in which the relief passage 6 is provided in the fuel pumping mechanism 40 has been described. However, the relief passage 6 is omitted, and the delivery pipe 4 is used as shown in the first embodiment. A mode in which the return passage 10 is provided may be employed. In this case, the state where all of the fuel pumped from the fuel pumping mechanism 40 flows in and the state where the fuel discharged from the delivery pipe 4 has the same amount as the fuel injection amount are appropriately switched. The target to be sequentially accumulated may be switched between the pump discharge amount Qp and the fuel injection amount Qinj. Even in this case, the above-described effects can be achieved.

  In the second embodiment, the example in which the fuel pump 41 configured to switch the fuel pressure supplied to the delivery pipe 4 between the low pressure state and the high pressure state is shown. A fuel pump configured to be switchable to a pressure state may be employed. Even in this case, the fuel injection amount can be appropriately controlled by switching the pressure of the fuel supplied to the delivery pipe 4 in accordance with the operation state of the internal combustion engine and the alcohol concentration of the fuel, and at least the above ( Each effect shown to 1)-(4) can be show | played.

  Furthermore, in the second embodiment, the example in which the fuel pump 41 configured to be able to switch the pressure of the fuel supplied to the delivery pipe 4 between the low pressure state and the high pressure state is shown. In order to keep the fuel pressure 4 constant, a fuel pump that pumps fuel at the same discharge pressure may be employed. In this case, the fuel injection valve capable of appropriately controlling the fuel injection amount over a wide range from when the fuel used is 100% gasoline to when the alcohol concentration is the highest concentration (85% in this embodiment). Should be adopted. Even in this case, at least the effects shown in the above (1) to (4) can be achieved.

  The execution modes of the air-fuel ratio feedback control, the concentration learning process, and the air-fuel ratio learning process shown in the above embodiments are not limited to these examples. That is, as long as the fuel injection amount can be corrected based on the deviation tendency between the air-fuel ratio AF and the stoichiometric air-fuel ratio SAF according to the output value of the air-fuel ratio sensor 24, it can be changed as appropriate.

  In each of the above embodiments, the fuel pumps 2 and 41 and the delivery pipe 4 are communicated with each other through the supply passage 3, and only the relief passage 6 is connected in the middle of the supply passage 3. . However, an example in which a fuel passage is further branched from the supply passage 3 may be employed. Even in this case, the concentration learning period is set based on the integrated amount of inflow into the delivery pipe 4 so as to be an appropriate period in which the change in the air-fuel ratio due to the change in the alcohol concentration of the fuel occurs. By executing the abnormality diagnosis process in a period other than the period, the operational effects shown in (1) above can be achieved.

  In each of the above embodiments, an example is shown in which ethanol is used as the alcohol used as the fuel. However, different alcohols such as methanol, propanol, and butanol can be used as long as the alcohol is guaranteed to be usable in the internal combustion engine. It can also be used as fuel. Even in this case, the above-described effects can be achieved.

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank 2,41 ... Fuel pump, 3 ... Supply passage, 4 ... Delivery pipe, 5 ... Fuel injection valve, 6 ... Relief passage, 7 ... Switching valve, 8 ... Low pressure pusher regulator, 9 ... High pressure pressure regulator, DESCRIPTION OF SYMBOLS 10 ... Return path, 20 ... Electronic control unit (Air-fuel ratio feedback means, learning means, abnormality diagnosis means), 21 ... Fuel level gauge, 22 ... Air flow meter, 23 ... Rotational speed sensor, 24 ... Air-fuel ratio sensor, 30, 40 ... fuel pumping mechanism, 41 ... pressure regulator.

Claims (8)

A fuel supply system is provided for supplying alcohol fuel in the fuel tank to the delivery pipe through the supply passage from the fuel pumping mechanism and to the internal combustion engine through a fuel injection valve connected to the delivery pipe. Air-fuel ratio feedback means for performing air-fuel ratio feedback control for correcting the fuel injection amount of the fuel injection valve so as to coincide with the theoretical air-fuel ratio according to the alcohol concentration of the fuel, and the actual air-fuel ratio and the theoretical air-fuel ratio obtained through the control And a learning means for executing a concentration learning process for updating an alcohol concentration learning value for correcting the fuel injection amount based on a deviation tendency between the fuel supply system and an abnormality diagnosis for executing an abnormality diagnosis process for the fuel supply system based on the deviation tendency An internal combustion engine fuel supply system abnormality diagnosis device comprising:
Refueling determination means for determining that the tank has been refueled;
Calculating means for calculating an integrated amount of fuel flowing into the delivery pipe after determining that refueling has been performed;
The learning means replaces the fuel in the delivery pipe with the fuel after refueling after the accumulated inflow amount after the fuel supply is determined reaches the amount at which the fuel in the fuel tank starts to be supplied to the delivery pipe. The period until the amount is reached is the concentration learning period, and the concentration learning process is executed only during the same period,
The fuel supply system abnormality diagnosis apparatus for an internal combustion engine, wherein the abnormality diagnosis unit executes the abnormality diagnosis process based on the deviation tendency in a period excluding the concentration learning period. The fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 1, wherein the abnormality diagnosis unit includes a period from when it is determined that refueling has been performed to when the concentration learning process is started as an execution period of the abnormality diagnosis process. In the fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 1 or 2,
The learning means is provided with a start time determination means for determining that the concentration learning processing start time is a time when the inflow integrated amount becomes equal to or larger than the volume of the supply passage and the condition is satisfied. An abnormality diagnosis device for a fuel supply system of an internal combustion engine, characterized by comprising: The fuel supply system abnormality diagnosis device for an internal combustion engine according to any one of claims 1 to 3,
The learning means is provided on the condition that the accumulated inflow amount is equal to or greater than a predetermined amount determined by the volume of the supply passage and the volume of the delivery pipe, and when the condition is satisfied, the concentration learning process ends. A fuel supply system abnormality diagnosis device for an internal combustion engine, comprising: an end timing determination means for determining the effect. The end time determining means determines that the concentration learning process ends when the following conditions are satisfied, where ΣQdel is the inflow integrated amount, Va is the volume of the supply passage, and Vb is the volume of the delivery pipe.

ΣQdel ≧ Va + Vb · α
α: 2.5 ≦ α ≦ 3.5

The fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 4. The fuel supply of the internal combustion engine according to any one of claims 1 to 5, wherein the fuel pumping mechanism is capable of switching at least a pressure of fuel supplied to the delivery pipe between a high pressure state and a low pressure state lower than the high pressure state. System abnormality diagnosis device. The fuel supply system is provided with a return passage for returning surplus fuel of the delivery pipe to the fuel tank, and a valve that is provided in the return passage and opens when the fuel pressure of the delivery pipe is equal to or higher than a predetermined valve opening pressure. A pressure valve,
The fuel pumping mechanism is connected to a fuel pump that supplies fuel in the fuel tank to the delivery pipe through the supply passage, and is connected to the downstream side of the fuel pump in the supply passage, and the fuel in the supply passage is supplied to the fuel A relief passage returning to the tank, and a switching valve for switching a communication state between the relief passage and the supply passage,
The switching valve is opened and the fuel in the supply passage is returned to the fuel tank through the relief passage to set the fuel pressure of the delivery pipe to the low pressure state, while the switching valve is closed. Opening the pressure valve and returning the excess fuel of the delivery pipe to the fuel tank through the return passage to set the fuel pressure of the delivery pipe to the high pressure state,
The calculating means calculates the inflow integration amount based on the fuel injection amount of the fuel injection valve when the switching valve is opened, while the inflow integration amount is based on the fuel pumping amount of the fuel pump when the switching valve is closed. The fuel supply system abnormality diagnosis device for an internal combustion engine according to claim 6, wherein the amount is calculated. The fuel supply system abnormality diagnosis for an internal combustion engine according to claim 7, wherein the fuel pumping mechanism maintains the fuel pressure of the delivery pipe at the high pressure state after the concentration learning period elapses after it is determined that refueling has been performed. apparatus.

Images