JP2008019830A - Fuel concentration learning device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly learn fuel concentration after fuel supply, in an internal combustion engine operable with alcohol mixed fuel. <P>SOLUTION: The engine ECU 30 updates a fuel concentration learning value for correcting a fuel supply quantity to the internal combustion engine according to the fuel concentration based on difference from a reference value of an air/fuel ratio correction quantity obtained by an air-fuel ratio control. This leaning process for update starts when the fuel is supplied to a fuel tank 2. When starting the leaning process, the fuel concentration after fuel supply is estimated from the fuel supply quantity, a type of supplied fuel and the fuel concentration leaning value before the fuel supply and is reflected on the fuel concentration leaning value. Immediately after the fuel supply, the fuel is circulated via a pressure regulator 12 by driving a fuel pump 20 and the fuel after the fuel supply in a fuel pipe 4 and a delivery pipe 8 is replaced quickly by the fuel after fuel supply and a purge control is inhibited while executing the learning process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel concentration learning device that learns a fuel concentration from a change in an operating state of an internal combustion engine in an internal combustion engine that can be operated with an alcohol-mixed fuel and that performs air-fuel ratio control.

  Conventionally, in an internal combustion engine that can be operated with alcohol-mixed fuel, if the fuel concentration changes, the optimum air-fuel ratio for reducing harmful components in the exhaust also changes, so the fuel concentration is detected and detected. The result is reflected in the fuel supply amount.

Further, when this type of control is performed, if a concentration sensor is used to detect the fuel concentration, the internal combustion engine cannot be optimally controlled when the concentration sensor fails.
Therefore, conventionally, the fuel concentration is learned on the basis of the deviation from the reference value of the air-fuel ratio correction amount (specifically, the average value) obtained during the execution of the air-fuel ratio control of the internal combustion engine, and the internal combustion engine is sent to the internal combustion engine based on the learned value. It is proposed to control the air-fuel ratio of the fuel mixture supplied to the internal combustion engine to an optimum air-fuel ratio for reducing harmful components in the exhaust gas by correcting the fuel supply amount (for example, (See Patent Document 1).

  That is, when the fuel concentration changes, the exhaust component discharged from the internal combustion engine also changes, and the detection signal from the air-fuel ratio sensor that detects the air-fuel ratio from the oxygen concentration in the exhaust also changes. In view of this, the proposed apparatus takes in the air-fuel ratio correction amount required when executing the air-fuel ratio control for controlling the fuel supply amount so that the air-fuel ratio detected by the air-fuel ratio sensor becomes the target value. By learning the fuel concentration based on the deviation of the amount from the reference value, the fuel concentration can be detected without using a concentration sensor.

  On the other hand, in the proposed apparatus, after the fuel concentration changes due to fuel supply to the fuel tank, the exhaust component of the internal combustion engine changes due to the change in concentration, and the air-fuel ratio correction amount is gradually updated in accordance with the change. When the value is stabilized, the fuel concentration can be accurately learned. Therefore, there is a problem that it takes time until the fuel concentration can be accurately learned.

Therefore, in order to estimate the fuel concentration faster, the fuel supply to the fuel tank is monitored, and when fuel supply to the fuel tank is made, the amount of fuel supplied to the internal combustion engine is forcibly increased or decreased, and the increase is increased. It has also been proposed to estimate the fuel concentration by detecting the behavior of the detection signal from the air-fuel ratio sensor accompanying the decrease (see, for example, Patent Document 2).
Japanese Patent Laid-Open No. 5-163992 JP 2003-120363 A

  However, if the fuel supply amount to the internal combustion engine is forcibly increased or decreased to estimate the fuel concentration, the air-fuel ratio of the fuel mixture supplied to the internal combustion engine will fluctuate greatly due to the increase or decrease. The harmful components in the exhaust cannot be removed by the exhaust system catalyst, etc., and the harmful components are temporarily discharged to the surroundings, or the fuel mixture becomes too lean and causes misfire, It can be considered.

  In order to prevent this problem, the increase / decrease in the fuel supply amount may be reduced. However, if the increase / decrease is reduced, the change in the detection signal from the air-fuel ratio sensor also becomes smaller, so the estimation of the fuel concentration is reduced. Accuracy is reduced.

  Further, in the method of estimating the fuel concentration by increasing / decreasing the fuel supply amount as described above, the detection signal from the air-fuel ratio sensor corresponds to the supplied fuel amount after increasing or decreasing the fuel supply amount. Since it is necessary to monitor the behavior of the detection signal until the value changes, the time required for estimating the fuel concentration cannot be sufficiently shortened.

  Even if the fuel concentration is learned (estimated) by any of the methods described above, all the fuel remaining in the fuel supply path for supplying fuel from the fuel tank to the fuel injection valve after refueling to the fuel tank Until the fuel in the fuel supply path is consumed and the fuel in the fuel tank is replaced with the fuel in the fuel tank, the fuel concentration cannot be accurately learned (estimated), which is required for learning (estimating) the fuel concentration. There is also a problem that the time becomes longer.

  The present invention has been made in view of these problems. In an internal combustion engine that can be operated with an alcohol-mixed fuel, the fuel concentration in the fuel tank can be reduced without affecting the operation of the internal combustion engine after refueling the fuel tank. The purpose is to be able to learn in a short time.

  The fuel concentration learning device according to claim 1, which has been made to achieve the above object, is based on a change in an operating state of the internal combustion engine (for example, from a reference value of an air-fuel ratio correction amount obtained when air-fuel ratio control of the internal combustion engine is executed). The fuel concentration of the fuel supplied to the internal combustion engine is learned on the basis of the deviation). When the fuel tank is refueled, the refueling detection means detects that, and the fuel type determination means determines the type of fuel supplied.

  Further, when the fuel type determining means determines the type of fuel supplied, the fuel concentration estimating means converts the determined fuel type, the amount of fuel supplied to the fuel tank, and the learned value of the fuel concentration before refueling. Based on this, the fuel concentration after refueling is estimated, and the estimation result is reflected in the learned value of fuel concentration.

  Therefore, according to the fuel concentration learning device of the present invention, it is possible to shorten the time required for the fuel concentration learning value to become a value corresponding to the actual fuel concentration after the fuel tank is refueled. .

  In the present invention, the fuel concentration is estimated using the type of fuel supplied, the amount of the fuel, and the learned value of the fuel concentration before refueling, and the fuel supply amount is increased or decreased for the estimation. Since there is no need, it is possible to stably operate the internal combustion engine without deteriorating exhaust emissions or causing misfire of the internal combustion engine at the time of estimation.

  In the present invention, when estimating the fuel concentration after refueling, since the type of fuel that has been refueled and the amount of fuel used are used, it is necessary to obtain these parameters after refueling. And each of these parameters may be manually input by the user after refueling, but the amount of fuel that has been refueled can be obtained from the output change of the fuel gauge normally provided in the fuel tank, Since the type of fuel supplied can be determined from the change in the detection signal from the air-fuel ratio sensor after refueling, these parameters may be acquired automatically based on the output from the fuel gauge or air-fuel ratio sensor.

  Further, as in the prior art described above, the air-fuel ratio correction amount obtained at the time of executing the air-fuel ratio control of the internal combustion engine is usually used for learning the fuel concentration, and the deviation from the reference value of the air-fuel ratio correction amount is used. The learning value of the fuel concentration is updated based on this, but a parameter other than the air-fuel ratio correction amount may be used for learning the fuel concentration.

  In other words, since the fuel concentration can be learned from the operating state of the internal combustion engine that changes depending on the fuel concentration, parameters other than the air-fuel ratio correction amount (for example, the oxygen concentration in the exhaust gas) can be used as long as the parameters represent such operating states. Even if used, the fuel concentration can be learned.

  On the other hand, when the fuel concentration is learned from the change in the operating state of the internal combustion engine as in the present invention, the fuel in the fuel supply passage from the fuel tank to the fuel injection valve is not completely replaced with the fuel in the fuel tank. And the fuel concentration after refueling cannot be learned accurately.

  Accordingly, in order to shorten the time required for replacement of the fuel in the fuel supply path so that the fuel concentration can be learned more quickly, the internal combustion engine includes an internal fuel supply path. A pressure regulator is provided to return the fuel supplied to the fuel injection valve to the fuel tank via the return path when the fuel pressure of the fuel exceeds the set pressure, and fuel supply to the fuel tank is detected by the fuel supply detection means In this case, the fuel circulation control means drives the fuel pump that discharges fuel from the fuel tank to the fuel supply path so that the fuel pressure in the fuel supply path exceeds the set pressure of the pressure regulator. This fuel may be replaced with the fuel in the fuel tank after refueling.

  In this way, after the fuel tank is refueled, the time until the fuel concentration in the fuel supply path becomes the fuel concentration after refueling can be shortened, and the fuel concentration can be learned in a short time. Until the fuel in the fuel supply path is replaced with the fuel in the fuel tank by the operation of the fuel circulation control means, the fuel concentration estimation means reflects the estimation result of the fuel concentration as it is in the fuel concentration learning value. Then, during this time, the fuel concentration learned value is excessively corrected, and the time until the learned value becomes stable may be increased.

  Therefore, the fuel concentration estimation means, as described in claim 3, from when the fuel supply to the fuel tank is detected by the fuel supply detection means until the replacement of the fuel in the fuel supply path by the fuel circulation control means is completed. During this period, the fuel concentration estimation result is corrected so that the amount of change from the fuel concentration learning value before refueling becomes smaller as the fuel circulation time is shorter, and is reflected in the fuel concentration learning value. desirable.

  In other words, in this way, not only the time until the fuel concentration in the fuel supply path becomes the fuel concentration after refueling after refueling to the fuel tank can be shortened, but also the learned value of the fuel concentration during that time. It is possible to prevent excessive correction and to shorten the time required for the learned value of the fuel concentration to stabilize after refueling.

  When the fuel supply detection means detects fuel supply to the fuel tank, the fuel circulation control means drives the fuel pump to replace the fuel in the fuel supply path with the fuel in the fuel tank after fuel supply. As long as the fuel concentration learning device is configured to learn the fuel concentration from the change in the operating state of the internal combustion engine, such as a deviation from the reference value of the air-fuel ratio correction amount, even a device that does not include the fuel concentration estimating means Can be applied.

  In other words, as described in claim 4, even in the fuel concentration learning device that does not include the fuel concentration estimating means, when the fuel tank is supplied with fuel, the fuel pump is driven to If the fuel in the fuel tank after refueling is replaced, the time required for the fuel supplied to the internal combustion engine to change to the fuel in the fuel tank after refueling is shortened. Learning can be performed in a short time.

  Next, since fuel supply to the fuel tank is normally performed while the operation of the internal combustion engine is stopped, the fuel circulation control means is provided to the fuel supply detection means while the operation of the internal combustion engine is stopped, as described in claim 5. When fuel supply to the fuel tank is detected, the fuel pump may be driven to replace the fuel in the fuel supply path with the fuel in the fuel tank after fuel supply.

  Further, when refueling during operation of the internal combustion engine is permitted, the fuel circulation control means drives the fuel pump to supply fuel even when refueling is detected by the refueling detection means during operation of the internal combustion engine. The fuel in the path may be replaced with the fuel in the fuel tank after refueling. In this case, as described in claim 6, the fuel circulation time (required for replacement of the fuel in the fuel tank) In other words, it is desirable to increase the fuel pump drive time) more than when the internal combustion engine is stopped.

  This is because during operation of the internal combustion engine, the fuel pressure in the fuel supply path decreases when the fuel injection valve is opened, and the amount of fuel returned from the pressure regulator to the fuel tank via the return path decreases. .

  Therefore, according to the fuel concentration learning device of the sixth aspect, the fuel pump is driven to reduce the fuel pressure drop in the fuel supply path caused by the fuel injection from the fuel injection valve during the operation of the internal combustion engine. By compensating for the fuel circulation time to circulate the fuel, it is circulated through the path from the fuel tank to the fuel tank through the fuel supply path, pressure regulator, and return path regardless of whether the internal combustion engine is operating or stopped. The amount of fuel can be set to the amount of fuel required to replace the fuel in the fuel supply path with the fuel in the fuel tank.

  On the other hand, when fuel is supplied to the fuel tank and the fuel is circulated during the operation of the internal combustion engine, the fuel pump is already driven to replenish the fuel supply path with the fuel injection from the fuel injection valve. Sometimes. Therefore, when the fuel circulation control means is operated when the fuel supply detection means detects fuel supply during operation of the internal combustion engine, the fuel circulation control means may be configured as described in claim 7.

  That is, the fuel circulation control means according to claim 7 determines whether or not the fuel pump is driven when the fuel supply detection means detects fuel supply to the fuel tank. If the fuel pump is not driven, the fuel circulation control means After the pump is driven and the fuel in the fuel supply path is replaced with the fuel in the fuel tank after refueling, the drive of the fuel pump is stopped, and if the fuel pump is driven, the fuel from the fuel pump The discharge amount is increased, the fuel in the fuel supply path is replaced with the fuel in the fuel tank after refueling, and then the fuel discharge amount from the fuel pump is returned to the original discharge amount.

  Therefore, according to the fuel circulation control means described in claim 7, when fuel is supplied to the fuel tank and the fuel is circulated during the operation of the internal combustion engine, the fuel is injected from the fuel injection valve through the fuel supply path. Therefore, it is possible to prevent the amount of fuel circulated from decreasing, and to quickly replace the fuel in the fuel supply path with the fuel in the fuel tank.

  Next, the fuel supply detection means for detecting the fuel supply to the fuel tank may detect the fuel supply to the fuel tank when the fuel tank cover is opened, for example. However, the fuel tank is not always refueled, and more preferably, when the fuel amount in the fuel tank is increased by a predetermined fuel refueling amount or more as described in claim 8, It may be determined that refueling is performed.

In this way, the fuel supply to the fuel tank can be easily and accurately detected from the output change of the fuel gauge provided in the fuel tank.
Further, the fuel concentration learning may be executed at all times. However, since the fuel concentration learning device of the present invention is provided with a fuel supply detecting means for detecting fuel supply to the fuel tank, this fuel supply is performed. The fuel concentration may be learned until the learning value of the fuel concentration becomes substantially constant after the fuel supply is detected by the detection means.

  For this purpose, as described in claim 9, when the refueling detection means detects refueling, the refueling history is stored, and then the air-fuel ratio is controlled by controlling the fuel supply amount based on the learning result of the fuel concentration. When the deviation from the reference value of the correction amount becomes equal to or less than the set value, there is provided a fuel supply history holding unit that determines that the learning of the fuel concentration is completed and erases the memory of the fuel supply history. It is advisable to learn the fuel concentration only when it is stored.

  That is, in this way, the fuel concentration is learned when the control device of the internal combustion engine is executing the air-fuel ratio control only when the fuel concentration needs to be learned after refueling the fuel tank. In other words, unnecessary learning operations in the control apparatus for the internal combustion engine are prohibited, and the processing burden due to learning of the fuel concentration can be reduced.

  Further, according to the fuel concentration learning device of the ninth aspect, after the fuel supply to the fuel tank, the fuel supply history holding means holds the fuel supply history until the fuel concentration learning is completed. After that, even if the control device stops operating with the operation stop of the internal combustion engine before the fuel concentration learning is completed after the control device of the internal combustion engine starts air-fuel ratio control, the control device is started after that. When the air-fuel ratio control is started, learning of the fuel concentration is resumed, and the learning of the fuel concentration can always be completed after refueling the fuel tank.

  On the other hand, there is known a control device for an internal combustion engine configured to execute purge control for supplying evaporated fuel from a fuel tank to an intake system of the internal combustion engine. When the purge control is executed during the fuel concentration learning, the air-fuel ratio of the fuel mixture supplied to the internal combustion engine shifts to the rich side and the fuel concentration learning value also fluctuates. Will do.

For this reason, the fuel concentration learning apparatus of the present invention may be provided with purge control prohibiting means for prohibiting execution of purge control during learning of the fuel concentration, as described in claim 10.
In this way, it is possible to prevent the learning value of the fuel concentration from being changed by the purge control and increasing the time required for learning the fuel concentration.

Embodiments of the present invention will be described below with reference to the drawings.
First, FIG. 1 is a configuration diagram showing a configuration of a fuel supply system that supplies alcohol mixed fuel from a fuel tank 2 to an internal combustion engine in an automobile.

  The fuel tank 2 is for storing a mixed fuel of alcohol and gasoline (alcohol mixed fuel) necessary for operating an internal combustion engine (not shown), and the alcohol mixed fuel (hereinafter simply referred to as fuel) is stored inside. ) Is pumped out, and a fuel pump 10 is provided via the fuel pipe 4 to a delivery pipe 8 connected to a fuel injection valve (injector) 6 of each cylinder of the internal combustion engine.

  The delivery pipe 8 is provided with a pressure regulator 12 that returns the internal fuel to the fuel tank 2 via the return pipe 14 when the internal fuel pressure exceeds the set pressure. For this reason, the fuel pressure in the delivery pipe 8 can be adjusted to a constant pressure by the operations of the fuel pump 10 and the pressure regulator 12.

  The fuel tank 2 is connected to an evaporation line 18 that guides the evaporated fuel evaporated in the fuel tank 2 to the canister 16. The evaporated fuel accumulated in the canister 16 is purged when the purge control valve 20 is opened. It is supplied to the internal combustion engine via the line 22.

  That is, the opening end of the purge line 22 opposite to the canister 16 is connected to the intake pipe of the internal combustion engine, and the purge control valve 20 is an electronic control device (hereinafter referred to as engine ECU) 30 for controlling the internal combustion engine. The purge control is performed during the operation of the internal combustion engine to open the purge line 22. For this reason, the evaporated fuel accumulated in the canister 16 is sucked into the internal combustion engine by the negative pressure in the intake pipe when the purge control valve 20 is opened.

  A fuel gauge 24 for detecting the amount of fuel inside is provided in the fuel tank 2, and a fuel supply port of the fuel tank 2 is provided with a lid (lid) 25 that seals the supply port. A lid courtesy switch (hereinafter referred to as SW) 26 for detecting the open / closed state is provided.

  Further, since the fuel tank 2 is mounted on an automobile and the fuel supply port is provided inside the vehicle body, a fuel lid 27 is formed on the vehicle body to cover the supply port. The fuel lid 27 is provided with a fuel lid SW28 for detecting the open / closed state.

  The lid courtesy SW 26 and the fuel lid SW 28 are in an OFF state when the corresponding lid is closed, and are in an ON state when the lid is open.

  Further, the internal combustion engine has a rotation speed sensor 32 for detecting the rotation speed (NE) of the internal combustion engine, an intake air amount sensor 34 for detecting the intake air amount (Q), and oxygen in the exhaust gas as sensors for detecting the operating state. An air-fuel ratio sensor 36 for detecting the air-fuel ratio (A / F) from the concentration, etc. are provided.

  The detection signals from these sensors 32, 34, 36,... Are input to the engine ECU 30 together with the ignition SW 38, the switch signal from the lid courtesy SW 26, the fuel lid SW 28, and the detection signal from the fuel gauge 24. .

  The engine ECU 30 detects the operating state of the internal combustion engine by taking input signals from these parts, and based on the operating state, the fuel injection amount from the injector 6 provided in each cylinder of the internal combustion engine (specifically, the injector 6 The valve opening time is calculated and fuel injection control for driving the injector 6 is executed. As shown in FIG. 2, a microcomputer (hereinafter referred to as a microcomputer) 40 including a CPU, a ROM, a RAM and the like is mainly used. It is configured.

  Further, the engine ECU 30 is provided with a power supply IC 42 for supplying power to an internal circuit such as the microcomputer 40. The power supply IC 42 receives power supply from the battery 50 mounted on the vehicle and generates a power supply voltage for driving the internal circuit. When the main relay 52 is turned off, such as when the ignition SW 38 is turned off, the microcomputer 40 When the main relay 52 is turned on, such as when the ignition SW 38 is turned on, the microcomputer 40 and other internal circuits are generated. A main power supply voltage having a large amount of power necessary for normal operation is generated.

  The engine ECU 30 is also provided with a main relay drive circuit 44 for driving the main relay 52. The main relay drive circuit 44 drives (turns on) the main relay 52 when the ignition SW 38 or the fuel lid SW 28 is turned on while the sub power supply voltage is supplied from the power supply IC 42, and the main relay 52 to the power supply IC 42. By supplying the battery voltage, the power supply IC 42 generates a main power supply voltage, and the microcomputer 40 and other internal circuits are normally operated. Then, after the main relay 52 is driven (ON), the main relay drive circuit 44 turns off the ignition SW 38 and the fuel lid SW 28, and when the microcomputer 40 shifts to the standby state, the main relay 52 is driven by a command from the microcomputer 40. Stop (OFF).

  Therefore, the microcomputer 40 and other internal circuits in the engine ECU 30 operate normally upon receiving the main power supply voltage from the power supply IC 42 if the ignition SW 38 or the fuel lid SW 28 is in the ON state, and both the ignition SW 38 and the fuel lid SW 28 are in the OFF state. When the power is on, the sub power supply from the power supply IC 42 holds the standby state.

  Next, in the above-described fuel injection control, the microcomputer 40 determines the basic injection amount based on the rotation speed (NE) detected by the rotation speed sensor 32 and the intake air amount (Q) detected by the intake air amount sensor 34. By calculating and correcting the basic injection amount based on the temperature (cooling water temperature) of the internal combustion engine, the fuel injection amount from the injector 6 is determined, and the injector 6 is driven according to the fuel injection amount. Executed.

  Further, the microcomputer 40 mixes the fuel supplied to the internal combustion engine based on the detection signal from the air-fuel ratio sensor 36 as illustrated in FIG. 18 during the steady operation other than the warm-up operation or acceleration / deceleration operation of the internal combustion engine. It is determined whether the excess air ratio is lean (lean air-fuel ratio) higher than the optimum value “1”, or whether the excess air ratio is rich (excess air-fuel ratio) lower than the optimum value “1”. Then, the air-fuel ratio correction amount is updated (increased or decreased) according to the determination result, and the fuel injection amount is corrected by this air-fuel ratio correction amount, so that the air-fuel ratio of the fuel mixture supplied to the internal combustion engine is targeted. Air-fuel ratio control for controlling the air-fuel ratio is also executed.

  At the time of executing the air-fuel ratio control, the microcomputer 40 detects a deviation from the reference value (correction amount: zero) of the average value of the air-fuel ratio correction amount updated by the air-fuel ratio control as a main process related to the present invention. The fuel concentration learning process for learning the concentration of the fuel in the fuel tank 2 (in this embodiment, the alcohol concentration) is also executed based on the obtained deviation.

  Further, the microcomputer 40 refuels for detecting that fuel (gasoline or alcohol) is supplied to the fuel tank 2, or drives the fuel pump 20 after refueling the fuel tank 2 to inject the fuel from the fuel tank 2. A fuel circulation process is also performed in which the fuel in the fuel supply path (fuel pipe 4 and delivery pipe 8) leading to 6 is replaced with the fuel in the fuel tank 2.

Hereinafter, the fuel supply process, the fuel circulation process, and the fuel concentration learning process executed by the microcomputer 40 will be described.
FIG. 4 is a flowchart showing an oil supply process executed by the microcomputer 40.

  This refueling process is a process that is repeatedly executed during the normal operation of the microcomputer 40. When this process is started, first, in S110 (S represents a step), it is determined whether or not the fuel lid SW28 is in an ON state. By determining, it is determined whether or not the fuel lid 27 covering the fuel supply port of the fuel tank 2 is open.

  If the fuel lid SW28 is in the OFF state (fuel lid 27: closed), the fuel supply process is terminated. Conversely, if the fuel lid SW28 is in the ON state (fuel lid 27: open), the process proceeds to S120. It is determined whether or not the microcomputer 40 is activated this time because the fuel lid SW 28 is turned on and the main relay 52 is driven by the main relay drive circuit 44.

  If it is determined in S120 that the current activation is because the fuel lid SW28 is turned on and the main relay 52 is driven, in S130, the activation history (activation history by the fuel lid SW28) indicating that is stored in the memory (RAM). And the process proceeds to S140.

  On the other hand, if it is determined in S120 that the microcomputer 40 has already been activated before the fuel lid SW28 is turned on, in S135, the memory of the activation history by the fuel lid SW28 is canceled, and the process proceeds to S140.

In S140, it is determined whether or not the fuel tank 2 has been actually refueled, and a refueling determination process (see FIG. 4), which will be described later, is performed to calculate the refueling amount when refueling has been performed.
In the subsequent S150, it is determined whether or not there is a refueling history to the fuel tank 2 based on a refueling history flag that is set (ON) when refueling is determined in the refueling determination process in S140. If it is determined that the refueling history flag is reset (OFF) and there is no refueling history in the fuel tank 2, an ECU power OFF process (see FIG. 5) described later is executed in S190, and then the refueling is performed. The process ends.

  Conversely, if it is determined in S150 that the refueling history flag is set (ON) and there is a refueling history to the fuel tank 2, after refueling fuel (gasoline or alcohol) to the fuel tank 2, In order to prohibit the purge control from being executed until the learning of the fuel concentration is completed, a purge control prohibition flag is set (ON) in S160, and the purge control valve 20 is driven in S170. Ban. Thereafter, an ECU power supply OFF process (see FIG. 5) described later is executed in S190, and the fuel supply process is terminated.

Next, the refueling determination process of S140 is executed according to the procedure shown in FIG.
That is, in the refueling determination process in S140, first, in S141, the amount of fuel in the fuel tank 2 before refueling is acquired.

  For example, when the process of S141 is first executed after it is determined in S110 that the fuel lid SW28 is turned on, the amount of fuel in the fuel tank 2 (that is, fuel supply) is determined. The previous fuel amount) is detected and stored in a memory (RAM or the like), and thereafter, the stored fuel amount is read out.

  Further, in the present embodiment, when the microcomputer 40 reads the fuel amount in the fuel tank 2 from the fuel gauge 24, the fuel amount in the fuel tank 2 is set to a constant unit (5 in the figure) as shown in FIG. The fuel level is expressed in stages (in liters), and this fuel level is read as the fuel amount.

  Next, in S142, it is determined whether or not the lid 25 that seals the fuel supply port of the fuel tank 2 has been opened by determining whether or not the lid courtesy switch 26 has been turned on.

  If the lid courtesy SW 26 is in the OFF state and the lid 25 remains closed, no fuel (gasoline or alcohol) is supplied to the fuel tank 2, and the fuel supply determination process is terminated as it is.

  On the other hand, if the lid courtesy SW 26 is ON and the lid 25 is open, the process proceeds to S143, and the current fuel amount (specifically, fuel level) in the fuel tank 2 is acquired via the fuel gauge 24.

  In S144, the gasoline supplied to the fuel tank 2 after the lid 25 of the fuel tank 2 is opened by subtracting the fuel amount before refueling acquired in S141 from the current fuel amount acquired in S143. Alternatively, the oil supply amount of alcohol is calculated, and in S145, it is determined whether or not the calculated oil supply amount is equal to or greater than a predetermined oil supply determination amount.

In S145, when it is determined that the amount of fuel supply is not equal to or greater than the fuel supply determination amount, it is determined that the fuel supply has not yet been performed, and the fuel supply determination process ends.
Conversely, if it is determined in S145 that the amount of fuel supply is equal to or greater than the fuel supply determination amount, it is determined that fuel supply to the fuel tank 2 has been performed, and the fuel supply history flag is set (ON) in S146. At S147, a fuel circulation flag for executing a fuel circulation process, which will be described later, is set (ON), and further at S148, a fuel type determination indicating that it is necessary to determine the type of fuel supplied. The flag is set (ON), and the fuel supply determination process ends.

  The refueling history flag, the fuel circulation flag, and the fuel type determination flag that are set (ON) at the time of refueling determination, together with the purge control prohibition flag described above, even if the microcomputer 40 is in a standby state (ON / OFF) State) can be stored in a memory (RAM) area.

Next, the ECU power-off process in S190 is executed according to the procedure shown in FIG.
That is, in this ECU power-off process, first, in S191, it is determined whether or not the fuel lid 27 is closed and the fuel lid SW28 is turned off.

  If the fuel lid SW28 is not in the OFF state, the ECU power-off process is terminated as it is. If the fuel lid SW28 is in the OFF state, the process proceeds to S192, depending on whether or not the fuel circulation flag is reset (OFF). It is determined whether or not fuel circulation by fuel circulation processing to be described later is not executed.

  Next, when it is determined in S192 that the fuel circulation flag is set (ON) and fuel circulation is currently being executed by the fuel circulation process, the ECU power OFF process is terminated as it is, and in S192. If it is determined that the fuel circulation flag has been reset (OFF) and fuel circulation by the fuel circulation process has not been executed, the process proceeds to S193, where it is determined whether there is an activation history by the fuel lid SW28.

  If there is no activation history by the fuel lid SW28, the ECU power-off process is terminated as it is. If there is an activation history by the fuel lid SW28, the process proceeds to S194, and the main relay drive circuit 44 is set to return the engine ECU 30 to the standby state. The main relay 52 is turned off by outputting a command to turn off the main relay 52, and the ECU power-off process is terminated.

Next, FIG. 6 is a flowchart showing a fuel circulation process executed by the microcomputer 40.
In this fuel circulation process, immediately after the fuel (gasoline or alcohol) is supplied to the fuel tank 2, the fuel pump 20 is driven so that the discharge flow rate of the fuel becomes a large flow rate. Are circulated in the order of fuel pipe 4 → delivery pipe 8 → pressure regulator 12 → return pipe 14 → fuel tank 2 in the fuel supply path (fuel pipe 4 and delivery pipe 8) from the fuel tank 2 to the injector 6. This is a process for quickly replacing the fuel with the fuel in the fuel tank 2 after refueling, and is repeatedly executed during the normal operation of the microcomputer 40 as in the above-described refueling process.

  In this fuel circulation process, first, in S210, it is determined whether or not the fuel circulation flag is set (ON). If the fuel circulation flag is not set (ON), there is no need for fuel circulation. If the fuel circulation flag is set (ON), the process proceeds to S220, and the fuel circulation start process is executed.

  In this fuel circulation start process, as shown in FIG. 7, it is determined whether or not the fuel pump 20 is stopped (S221), and if the fuel pump 20 is stopped (S221: YES), the fuel pump 20 starts. The fuel pump 20 is driven so that the fuel discharge flow rate becomes large (S222), the drive history of the fuel pump by the fuel circulation process is stored (S223), and conversely, the fuel pump 20 is already driven. If so (S221: NO), whether the fuel pump 20 is driven so that the fuel discharge flow rate becomes a standard flow rate or is already driven so as to become a large flow rate for refueling during operation of the internal combustion engine. If the fuel pump 20 is driven so as to have a standard flow rate (S224: YES), the fuel discharge flow rate from the fuel pump 20 becomes a large flow rate. So as to drive the fuel pump 20 (S225), it is performed in Step like.

  As a result, the fuel is supplied from the fuel tank 2 to the injector 6 through the fuel pump 20 at a large flow rate, and the fuel pressure in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is increased and supplied to the injector 6. The fuel thus produced is returned from the pressure regulator 12 through the return pipe 14 into the fuel tank 2.

  Next, when the fuel circulation start process in S220 is completed, the process proceeds to S230, where fuel circulation by the fuel pump 20 is started in S220, and then in the fuel supply path (fuel pipe 4 and delivery pipe 8). A fuel circulation time calculation process for calculating a fuel circulation time required for replacing the fuel in the fuel tank 2 with the fuel in the fuel tank 2 is executed.

The fuel circulation time calculation process in S230 is executed according to the procedure shown in FIG.
That is, in the fuel circulation time calculation process, first, in S231, when the fuel pump 20 is driven at a large flow rate when the internal combustion engine is stopped, the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is transferred into the fuel tank 2. A preset time set as a time (or a slightly longer time) required for the replacement with the fuel is set as a reference fuel circulation time.

  Next, in subsequent S232, whether or not the internal combustion engine is in operation is determined by determining whether or not the internal combustion engine is rotating based on the detection signal from the rotation speed sensor 32 (rotational speed NE> 0?). If the internal combustion engine is not in operation, the process proceeds to S234. If the internal combustion engine is in operation, the process proceeds to S233.

  In S233, the fuel circulation time set in S231 is compensated for a decrease in the amount of fuel circulation caused by a decrease in pressure in the fuel supply path (fuel pipe 4 and delivery pipe 8) caused by fuel injection from the injector 6. Is added, the fuel circulation time is reset, and the process proceeds to S234.

  Next, in S234, it is determined whether or not fuel circulation has not been completed during the previous operation of the microcomputer 40 (previous trip). That is, when the microcomputer 40 is restarted by starting the internal combustion engine or the like after the fuel circulation is started in S220 until the fuel circulation is completed, the fuel circulation is Since it is interrupted in the middle, it is determined in S234 whether or not there has been such an interruption of the fuel circulation based on the fuel circulation continuation time described later.

  If it is determined in S234 that the fuel circulation in the previous trip is not incomplete, the process proceeds to S236, and conversely, in S234, it is determined that the fuel circulation in the previous trip has not been completed. In this case, from the fuel circulation time set at this time in S252 or S254, the time (fuel circulation continuation time) in which the fuel pump 20 was driven at a large flow rate during the previous operation of the microcomputer 40 and fuel was circulated was determined. By decrementing, the fuel circulation time is reset, and the process proceeds to S236.

  In S236, the latest fuel circulation time set in S231, S233, or S235 is determined as the fuel circulation time used for control, and the fuel circulation time calculation process is terminated.

  Next, when the fuel circulation time calculation process in S230 is completed, the process proceeds to S240, where a time counter for counting the time actually elapsed from the start of fuel circulation in S220 is initialized and incremented. As a result, the measurement of the fuel circulation continuation time is started.

  In the subsequent S250, the fuel pump 20 is driven by determining whether or not the fuel circulation continuation time obtained from the count value of the time counter incremented in S240 has exceeded the fuel circulation time calculated in S230. It is determined whether or not the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) has been replaced with the fuel in the fuel tank 2 (that is, whether or not the fuel circulation has been completed).

  If it is determined in S250 that the fuel circulation is not yet completed, the process returns to S240, the time counter is incremented, and the process of S250 is executed again, so that the fuel circulation time is started after the fuel circulation is started. Wait for it to continue.

  Next, if it is determined in S250 that the fuel circulation duration has exceeded the fuel circulation time and the fuel circulation has been completed, the fuel circulation flag is reset (OFF) in S260, and the fuel circulation is completed in S270. After executing the process, the fuel circulation process is terminated.

This fuel circulation end process is a process executed to restore the drive state of the fuel pump 20 corresponding to the fuel circulation end process of S220, and is executed according to the procedure shown in FIG.
That is, in the fuel circulation end process, it is determined whether or not the fuel pump 20 is currently driven (S271). If the fuel pump 20 is driven (S271: YES), the fuel circulation process of the fuel pump 20 is performed. It is determined whether the driving history is stored (S272). If the driving history of the fuel pump 20 is stored (S272: YES), the driving of the fuel pump 20 is stopped (S273), and the fuel circulation is performed. The driving history of the fuel pump 20 by the processing is deleted (S274). Conversely, if the driving history of the fuel pump 20 by the fuel circulation processing is not stored (S272: NO), the fuel pump 20 is driven at a large flow rate. If the fuel pump 20 is driven at a large flow rate (S275: YES), the fuel pump 20 is driven at a standard flow rate. Switching (S276), it is performed in Step like.

Next, FIG. 10 is a flowchart showing a fuel concentration learning process executed by the microcomputer 40.
This fuel concentration learning process is a process that is repeatedly executed together with the above-described refueling process and fuel circulation process during the normal operation of the microcomputer 40. When this process is started, first, in S310, the refueling history flag is set (ON). ), It is determined whether or not the fuel concentration learning has not been completed since the fuel supply to the fuel tank 2 is currently determined.

  If the refueling history flag is not set (ON), it is determined that the fuel concentration learning has ended, and the fuel concentration learning process is terminated as it is. Conversely, the refueling history flag is set (ON). If so, it is determined that the learning of the fuel concentration has not ended, the process proceeds to S320, and it is determined whether or not the purge control prohibition flag is set (ON).

  If it is determined in S320 that the purge control prohibition flag is not set (ON), purge control may be executed. Therefore, the fuel concentration learning process is terminated, and in S320 When it is determined that the purge control prohibition flag is set (ON), the process proceeds to S330, and it is determined whether or not the fuel type determination flag is reset (OFF).

  If the fuel type determination flag is not reset (OFF), the type of fuel that has been supplied cannot be specified after refueling the fuel tank 2, and the process proceeds to S380, where the fuel type determination process is performed. And the fuel concentration learning process is temporarily terminated.

Here, the fuel type determination process of S380 is executed according to the procedure shown in FIG.
That is, in the fuel type determination process, first, in S381, based on the detection signal from the air-fuel ratio sensor 36, it is determined whether or not the air-fuel ratio of the fuel mixture supplied to the internal combustion engine is lean. If there is, the process proceeds to S382, the rich continuation counter is cleared, the lean continuation counter is incremented in S383, and then the process proceeds to S384.

  In S384, it is determined whether or not the value of the lean continuation counter is greater than a preset fuel determination value, in other words, the time during which the air-fuel ratio is lean is the fuel determination value and the fuel concentration learning process execution period. It is determined whether or not it has become longer than the set time obtained by.

  If it is determined in S384 that the value of the lean continuation counter is equal to or less than the fuel determination value, the fuel type determination process is terminated as it is. Conversely, in S384, the value of the lean continuation counter is determined as the fuel determination value. If the air / fuel ratio is determined to be leaner than the set time, the alcohol concentration of the fuel supplied to the internal combustion engine has increased due to refueling (in other words, the gasoline concentration has decreased). Therefore, in S385, it is determined that the fuel supplied to the fuel tank 2 this time is alcohol, and the fact is stored in a memory (RAM or the like), and in S386, the fuel type determination flag is reset. (OFF), and the fuel type determination process ends.

  Next, if it is determined in S381 that the air-fuel ratio is rich, the process proceeds to S387, the lean continuation counter is cleared, and after the rich continuation counter is incremented in S388, the process proceeds to S389. .

  In S389, it is determined whether the time during which the air-fuel ratio is rich has become longer than the set time by determining whether the value of the rich continuation counter is greater than a preset fuel determination value. To do.

  If it is determined in S389 that the value of the rich continuation counter is equal to or less than the fuel determination value, the fuel type determination process is terminated as it is. Conversely, in S389, the value of the rich continuation counter is determined to be the fuel determination value. If the air-fuel ratio is determined to be richer than the set time, the alcohol concentration of the fuel supplied to the internal combustion engine has been lowered by refueling (in other words, the gasoline concentration has increased). Therefore, in S390, it is determined that the fuel supplied to the fuel tank 2 this time is gasoline, and that fact is stored in a memory (RAM or the like), and in S391, the fuel type determination flag is reset. (OFF), and the fuel type determination process ends.

  Returning to FIG. 10, if it is determined in S330 that the fuel type determination flag is reset (OFF), the process proceeds to S340, and it is determined whether or not a fuel concentration learning condition is satisfied. Note that the determination in S340 is, for example, that air-fuel ratio control is currently being performed, and that the air-fuel ratio has been reversed from lean to rich, or rich to lean, or that the deviation from the reference value of the air-fuel ratio correction amount is not. This is done by determining whether or not a preset threshold value has been exceeded.

  If it is determined in S340 that the fuel concentration learning condition is not satisfied, the fuel concentration learning process is terminated, and conversely, in S340, it is determined that the fuel concentration learning condition is satisfied. Then, the process proceeds to S350, and a fuel concentration learning value calculation process is performed in which the fuel concentration learning value is calculated based on the air-fuel ratio correction amount updated by the air-fuel ratio control.

  In the following S360, it is determined whether or not the calculation of the fuel concentration learning value by the fuel concentration learning value calculation processing in S350 is completed. If the calculation of the fuel concentration learning value is not completed, the fuel concentration learning processing is performed as it is. Exit.

  Conversely, if the calculation of the fuel concentration learning value has been completed, in order to prohibit the fuel concentration learning operation until the next refueling, the refueling history flag is reset (OFF) in S370, In order to permit the execution of the purge control, the purge control prohibition flag is reset (OFF) in S372, the purge control valve 20 is permitted to be driven in S374, and the fuel concentration learning process is terminated.

Next, FIG. 12 is a flowchart showing the fuel concentration learning value calculation process in S350.
As shown in FIG. 12, in the fuel concentration learning value calculation process, first, fuel supply to the fuel tank 2 is determined in S410, and fuel concentration learning by the fuel concentration learning value calculation process has been completed or has not been completed. Determine if it is complete.

  If the fuel concentration learning is completed, the fuel concentration learned value calculation process is terminated as it is. If the fuel concentration learning is not completed, the process proceeds to S420 and the fuel concentration learned value is set. A fuel concentration correction value for correcting to a value corresponding to the fuel concentration after refueling is calculated.

  In the fuel concentration correction value calculation process executed in S420, as shown in FIG. 13, first, after fuel supply to the fuel tank 2 is determined, the fuel concentration correction value is calculated in the fuel concentration correction value calculation process. Or whether the fuel concentration correction value has not been calculated (S421). If the calculation of the fuel concentration correction value has been completed (S421: YES), the fuel concentration correction value calculation processing is terminated. On the contrary, if the fuel concentration correction value has not been calculated (S421: NO), the fuel amount (fuel level) in the fuel tank 2 after refueling is acquired via the fuel gauge 24, and the fuel amount and the pre-refueling amount are acquired. The amount of fuel supplied to the fuel tank 2 is calculated by obtaining the difference from the amount of fuel (fuel level) (S422), and the fuel concentration learning value before refueling to the fuel tank 2 is acquired (S423). Refueling amount to 2 and fuel before refueling A degree learning value using the fuel concentration correction value calculation map as parameters to calculate the fuel density correction value (S424), is performed in Step like.

  The fuel concentration correction value calculation map, as shown in FIG. 16A, is a gasoline refueling map for obtaining a fuel concentration correction value when gasoline is supplied to the fuel tank 2, and FIG. As shown in b), two types of maps are prepared, namely, an alcohol refueling map for obtaining a fuel concentration correction value when alcohol is supplied to the fuel tank 2, and a fuel concentration correction value calculation process ( Specifically, in S424), a map used for calculating the fuel concentration correction value is selected based on the determination result of fuel supply fuel (gasoline or alcohol) by the fuel type determination process.

  Next, when the fuel concentration correction value calculation process of S420 is completed, the process proceeds to S430, and a fuel concentration correction limiting process for limiting the correction of the fuel concentration learning value by the fuel concentration correction value is executed.

  This fuel concentration correction limiting process is performed when fuel circulation by the above-described fuel circulation process is not completed (in other words, when the fuel supplied to the internal combustion engine is gradually changing to the fuel concentration after refueling). If the fuel concentration learning value is corrected using the fuel concentration correction value, the fuel concentration learning value is overcorrected. This is a process executed to limit the correction.

  In this fuel concentration correction limiting process, as shown in FIG. 14, first, in S431, it is determined whether or not the fuel circulation flag is set (ON), whereby the fuel circulation after refueling is completed. If the fuel circulation flag is reset (OFF) and the fuel circulation after refueling is completed, the fuel concentration correction restriction process is terminated as it is, and conversely, the fuel circulation flag is set. If it is (ON) and the fuel circulation is incomplete, the process proceeds to S432.

  Next, in S432, the amount of fuel (gasoline or alcohol) supplied to the fuel tank 2 calculated in S422 is acquired, and in S433, the fuel is obtained from the time counter that is sequentially incremented during fuel circulation in S240. Get the circulation duration.

  In the subsequent S434, the fuel concentration based on the fuel concentration correction value is obtained using the refueling amount and fuel circulation duration acquired in S432 and S433, and the correction restriction coefficient calculation map (see FIG. 17) using these values as parameters. A correction restriction coefficient (a value smaller than 1) for restricting correction of the learning value is calculated, and in S435, the fuel concentration correction value is corrected by multiplying the fuel concentration correction value by the calculated correction restriction coefficient, The fuel concentration correction restriction process ends.

  The correction limit coefficient calculation map indicates that the longer the amount of fuel supplied to the fuel tank 2, the longer it takes to replace the fuel in the fuel supply path (fuel pipe 4 and delivery pipe 8) with the fuel after refueling. Accordingly, as shown in FIG. 17, the correction limit coefficient is set to be smaller as the fuel circulation duration time is shorter and the amount of fuel supply is larger.

  Next, when the fuel concentration correction limiting process of S430 is completed, the process proceeds to S440, and the fuel obtained by the processes of S420 and S430 is added to the fuel concentration learning value (not including the correction value) that does not reflect the fuel concentration correction value. By adding the concentration correction value, a fuel concentration learning value (estimation) corresponding to the fuel concentration after refueling is calculated.

  In the subsequent S450, the fuel concentration learning value (estimated) calculated in S440 is updated based on the deviation from the reference value of the air-fuel ratio correction amount obtained in the air-fuel ratio control so that the deviation becomes smaller. The updated fuel concentration learning value (estimation) is set as the fuel concentration learning value used for correcting the fuel injection amount in the fuel injection control.

  In this process of S450, an average value of the air-fuel ratio correction amount read when the process of S450 was executed last time and the air-fuel ratio correction amount read this time is obtained, and the average value is determined according to the deviation from the reference value. The fuel concentration learning value (estimation) is corrected, and the procedure is executed. As illustrated in FIG. 18, when the fuel concentration learning processing is started and the processing of S450 is first executed (time point t1). Since there is no previous value of the air-fuel ratio correction amount, the fuel concentration learning value (estimated) obtained in S440 is set as it is as the fuel concentration learning value used for fuel injection control, and when the subsequent learning condition is satisfied ( At the time points t2, t3,...), The fuel concentration learning value is updated according to the deviation of the air-fuel ratio correction amount from the reference value.

  Next, when the fuel concentration learning value (estimation) is updated in S450, the process proceeds to S460, and the fuel concentration is determined in S440 according to the correction amount when the fuel concentration learning value (estimation) is updated in S450. The original fuel concentration learning value (not including the correction value) used to calculate the learning value (estimation) is updated.

  In the subsequent S470, it is determined whether or not the change rate of the fuel concentration learning value (not including the correction value) updated in S460 is within a predetermined percentage (for example, within 1%) set in advance. Is within the predetermined percentage, it is determined that the fuel concentration learned value has become a value corresponding to the fuel concentration, the process proceeds to S480, and the fuel concentration learned value updated in S460 (not including the correction value) is changed to S420. The fuel concentration learning value is obtained by adding the fuel concentration correction value obtained in the process of S430 and the fuel concentration learning value is corrected by the fuel injection control until the next refueling. Determined as the fuel concentration learning value to be used.

  In subsequent 490, the fact that the learning of the fuel concentration after refueling has been completed is stored, and the fuel concentration learning value calculation process is terminated. If it is determined in S470 that the change rate of the fuel concentration learning value (not including the correction value) is not within the predetermined percentage, the processing of S490 is not executed to continue the fuel concentration learning. Then, the fuel concentration learning value calculation process is terminated.

  As described above, the engine ECU 30 of the present embodiment causes the microcomputer 40 to normally operate to execute the fuel supply process not only when the ignition SW 38 is turned on but also when the fuel lid SW 28 is turned on.

  In this fuel supply process, it is determined whether fuel has been supplied to the fuel tank 2 by performing a fuel supply determination process (S140) when the fuel lid SW28 is in the ON state. For this reason, the engine ECU 30 side can detect fuel supply to the fuel tank 2 even when the internal combustion engine is stopped or in operation.

  In the fuel supply determination process, when the lid 25 of the fuel tank 2 is open, a fuel supply amount is obtained from the fuel amount detected by the fuel gauge 24. When the fuel supply amount is equal to or greater than the fuel supply determination amount, the fuel tank 2 is determined (S142 to S145), it is possible to accurately detect refueling.

  Next, when fuel supply to the fuel tank 2 is detected in the fuel supply determination process, a fuel type determination process (S380) for determining the fuel type supplied is executed in the fuel concentration learning process. This fuel type determination process When the fuel type is determined at, fuel concentration learning value calculation processing (350) is started.

  In this fuel concentration learning value calculation process, the fuel concentration learning value is corrected to the fuel concentration in the fuel tank after refueling based on the fuel type determined in the fuel type determination process and the fuel supply amount (S440). The corrected fuel concentration learned value is updated based on the deviation from the reference value of the air-fuel ratio correction amount (S450, S460), thereby updating the fuel concentration learned value (that is, learning the fuel concentration).

  Therefore, according to the present embodiment, as shown in FIG. 18, immediately after the fuel concentration learning value calculation process is executed (time point t1) after fuel supply to the fuel tank 2, the fuel concentration learning value is By the concentration correction value, it is corrected to a value corresponding to the fuel concentration after refueling, and until the fuel concentration learning value converges to an appropriate value corresponding to the actual fuel concentration by the subsequent fuel concentration learning value calculation processing. Time can be shortened.

  That is, in the conventional device that simply updates the fuel concentration learning value based on the deviation of the air-fuel ratio correction amount from the reference value, as shown in FIG. 19, the fuel concentration learning value is an appropriate value (in the figure, corresponding to the actual fuel concentration). However, in this embodiment, the fuel concentration correction value is obtained immediately after refueling to correct the fuel concentration learning value, so that the fuel concentration learning value is quickly changed close to the appropriate value. Thus, the time until the fuel concentration learning value converges to an appropriate value can be shortened.

  In the present embodiment, the fuel supply amount to the internal combustion engine is increased or decreased in estimating the fuel concentration after refueling to the fuel tank 2 (specifically, obtaining the fuel correction value and correcting the fuel concentration learning value). Therefore, the internal combustion engine can be operated stably without any deterioration of exhaust emission or misfire of the internal combustion engine.

  Further, in the present embodiment, the fuel concentration learning value calculation process is executed only when the refueling history flag is set, and this refueling history flag is used for the fuel tank in the refueling determination process. 2 is set when fueling to 2 is detected (S146), and when it is determined in the fuel concentration learning value calculation process that the fuel concentration learning value has converged to an appropriate value (specifically, the change rate of the fuel concentration learning value) (S370).

  For this reason, according to the present embodiment, learning of the fuel concentration can be performed only during a period after the fuel tank 2 is refueled until the fuel concentration learning value converges to an appropriate value. Can be reduced.

  Further, since the set / reset state of the refueling history flag is maintained even when the microcomputer 40 is in the standby state, for example, even if the microcomputer 40 enters the standby state when the learning of the fuel concentration is not completed, Thereafter, when the microcomputer 40 is activated, the fuel concentration learning is executed again. For this reason, the fuel concentration learning value can be made to correspond to the fuel concentration in the fuel tank 2 without always performing the fuel concentration learning.

  On the other hand, when fuel supply to the fuel tank 2 is detected in the fuel supply process, the fuel circulation flag is set together with the fuel supply history flag (S147). When this fuel circulation flag is set, the fuel pump 20 is driven by the fuel circulation process. However, it is driven so that the fuel discharge flow rate becomes a large flow rate.

  As a result, regardless of whether the internal combustion engine is operating or stopped, when fuel is supplied to the fuel tank 2, the fuel in the fuel supply path (fuel pipe 4 and delivery pipe 8) from the fuel tank 2 to the injector 6 is supplied. The fuel in the subsequent fuel tank 2 is promptly replaced, and the time until the fuel concentration learned value converges to an appropriate value in the fuel concentration learned value calculation process after refueling can be further shortened.

  Further, in the fuel circulation process, when the fuel pump 20 is driven to circulate the fuel during the operation of the internal combustion engine, the fuel circulation time is added to the fuel circulation time by adding a correction time to the fuel circulation time. It is longer than the circulation time (S233). For this reason, during operation of the internal combustion engine, the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is replaced with the fuel in the fuel tank 2 due to the pressure drop caused by the fuel injected from the injector 6. Even if the time required for the fuel becomes longer, the fuel circulation time can be set corresponding to the time, and the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is fueled by the fuel circulation processing. It is possible to reliably replace the fuel in the tank 2.

  Further, in the fuel circulation process, the fuel circulation flag used for determining whether or not to circulate the fuel by driving the fuel pump 20 is maintained even when the microcomputer 40 is in the standby state, similarly to the fuel supply history flag. The

  For this reason, even after the refueling, even if the microcomputer 40 is restarted in a state where the fuel circulation is not completed, the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is transferred to the fuel tank 2 by the fuel circulation process. The fuel can be replaced.

  The fuel circulation time at that time is set by reducing the previous fuel circulation continuation time (S235), so the drive time of the fuel pump 20 does not become unnecessarily long. The amount of power consumed can be minimized.

  In addition, when fuel is supplied to the fuel tank 2 during operation of the internal combustion engine, the fuel pump 20 may already be driven to supplement the fuel injected from the injector 6. Then, in driving the fuel pump 20 to circulate the fuel, if the fuel pump 20 has already been driven, the amount of fuel discharged from the fuel pump 20 is increased (S225), and the fuel circulation time has elapsed. When the fuel circulation is finished, the fuel discharge amount from the fuel pump 20 is returned to the original discharge amount (S276).

  Therefore, when fuel is supplied to the fuel tank 2 and the fuel is circulated during the operation of the internal combustion engine, the fuel is injected from the injector 6 and circulated through the fuel supply path (the fuel pipe 4 and the delivery pipe 8). The fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is promptly replaced with the fuel in the fuel tank by preventing the fuel amount from decreasing, and after the fuel is circulated, the fuel supply path ( The fuel supply to the fuel pipe 4 and the delivery pipe 8) can be continued.

  On the other hand, in the fuel concentration learning process, the fuel concentration learning value calculation process (S350) is also executed during the circulation of the fuel by the fuel circulation process. At this time, the fuel concentration correction limiting process (S430) is performed. The correction of the fuel concentration learning value is limited by correcting the fuel concentration correction value calculated in the value calculation process (S430) according to the fuel circulation duration time.

  Therefore, according to this embodiment, in the process in which the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is replaced with the fuel in the fuel tank 2, the fuel concentration learning value corresponds to the fuel concentration after replacement. It is also possible to prevent overcorrection to the corrected value, and to prevent the time required for the fuel concentration learned value to converge to an appropriate value due to overcorrection of the fuel concentration learned value.

  Furthermore, in this embodiment, when the fuel supply to the fuel tank 2 is detected in the fuel supply process and the fuel supply history flag is set, the purge control prohibit flag for prohibiting the purge control is set (S170), The driving (opening) of the purge control valve 20 is prohibited (S170). After the fuel concentration learning is completed, the purge control prohibiting flag is reset (S372), and the driving (opening) of the purge control valve 20 is performed. It is allowed (S374).

  For this reason, during the learning of the fuel concentration, the purge control valve 20 is opened by the purge control, the fuel vapor accumulated in the canister 16 is supplied to the intake system of the internal combustion engine, and the fuel concentration is supplied by the supplied fuel vapor. It is possible to prevent the learning value from fluctuating and increasing the time required for learning the fuel concentration.

  In the present embodiment, the engine ECU 30 functions as the fuel concentration learning device of the present invention, and among the processes executed by the microcomputer 40 of the engine ECU 30, the fuel supply determination process of FIG. 4 is the fuel supply detection means of the present invention. 11 corresponds to the fuel type determination means of the present invention, and the fuel circulation process of FIG. 6 corresponds to the fuel circulation control means of the present invention.

  In the fuel concentration learning value calculation processing of FIG. 12, the processing of S420 to S440 that calculates the fuel concentration correction value and corrects the fuel concentration learning value corresponds to the fuel concentration estimation means of the present invention, and is used for the fuel supply determination processing. The process of S146 and S370 that resets the fuel supply history flag when the fuel concentration learning value is calculated in the fuel concentration learning process, and the memory of the microcomputer 40 that stores the fuel supply history flag is set. The processing of S160 and S170 in which the purge control prohibition flag is set and the drive of the purge control valve 20 is prohibited in the refueling processing of FIG. 3 corresponds to the purge control prohibiting device of the present invention. To do.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the above embodiment, when fuel is supplied to the fuel tank 2, the fuel in the fuel supply path (the fuel pipe 4 and the delivery pipe 8) is used as the fuel in the fuel tank 2 in the fuel circulation process of FIG. 6. In the fuel concentration learning process of FIG. 10, the fuel concentration learning value (estimated) after refueling is obtained from the fuel concentration correction value and the fuel concentration learning value (not including the correction value) in the fuel concentration learning process of FIG. (Estimation) is updated so that learning of fuel concentration after refueling can be executed in a short time. However, these processes do not necessarily need to be executed in combination. In a conventional fuel concentration learning apparatus, refueling is performed. The time required for learning the fuel concentration can be shortened only by executing the fuel circulation process of FIG. 6 later, or by estimating the fuel concentration after refueling and reflecting it in the fuel concentration learning value.

It is a block diagram showing the structure of the fuel supply system which supplies alcohol mixed fuel to an internal combustion engine. It is a block diagram showing schematic structure of engine ECU. It is a flowchart showing the oil supply process performed with the microcomputer in engine ECU. It is a flowchart showing the oil supply determination process performed in S140 of FIG. It is a flowchart showing the ECU power supply OFF process performed in S190 of FIG. It is a flowchart showing the fuel circulation process performed with the microcomputer in engine ECU. It is a flowchart showing the fuel circulation start process performed in S220 of FIG. It is a flowchart showing the fuel circulation time calculation process performed in S230 of FIG. It is a flowchart showing the fuel circulation end process performed in S270 of FIG. It is a flowchart showing the fuel concentration learning process performed with the microcomputer in engine ECU. It is a flowchart showing the fuel classification determination process performed in S380 of FIG. It is a flowchart showing the fuel concentration learning value calculation process performed in S350 of FIG. It is a flowchart showing the fuel concentration correction value calculation process performed in S420 of FIG. It is a flowchart showing the fuel concentration correction | amendment limitation process performed in S430 of FIG. It is explanatory drawing explaining the operation | movement at the time of a microcomputer reading fuel amount from a fuel meter. It is explanatory drawing showing the map used for calculating a fuel concentration correction value. It is explanatory drawing showing the map used for calculating the correction | amendment limiting coefficient of a fuel concentration learning value. It is a time chart explaining the update operation | movement of the fuel concentration learning value of an Example. It is a time chart explaining the update operation | movement of the conventional fuel concentration learning value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 2 ... Fuel tank, 4 ... Fuel pipe, 6 ... Injector, 8 ... Delivery pipe, 10 ... Fuel pump, 12 ... Pressure regulator, 14 ... Return pipe, 16 ... Canister, 18 ... Evaporator line, 20 ... Purge control valve, 20 ... Fuel pump, 22 ... purge line, 24 ... fuel gauge, 25 ... lid, 26 ... lid courtesy SW, 27 ... fuel lid, 28 ... fuel lid SW, 30 ... engine ECU, 32 ... rotation speed sensor, 34 ... intake air amount sensor, 36 ... Air-fuel ratio sensor, 38 ... Ignition SW, 40 ... Microcomputer, 42 ... Power supply IC, 44 ... Main relay drive circuit, 50 ... Battery, 52 ... Main relay.

Claims (10)

The air-fuel ratio of the fuel mixture supplied to the internal combustion engine is detected from the exhaust components of the internal combustion engine that can be operated with the alcohol-mixed fuel, and the fuel supply amount to the internal combustion engine is adjusted so that the air-fuel ratio becomes the target air-fuel ratio. Fuel that is provided in a control device for an internal combustion engine that executes air-fuel ratio control to be corrected, learns the fuel concentration of the fuel supplied to the internal combustion engine from a change in the operating state of the internal combustion engine, and reflects it in the control of the fuel supply amount A concentration learning device,
Refueling detection means for detecting that fuel has been supplied to the fuel tank of the internal combustion engine;
A fuel type determination means for determining a type of fuel supplied when the fuel supply detecting means detects fuel supply to the fuel tank;
After the fuel supply to the fuel tank is detected by the fuel supply detection means, when the type of fuel supplied by the fuel type determination means is determined, the determined fuel type and the fuel tank are supplied. Fuel concentration estimation means for estimating a fuel concentration after refueling based on a fuel amount and a learned value of fuel concentration before refueling, and reflecting the estimated result in the learned value of fuel concentration;
A fuel concentration learning device for an internal combustion engine, comprising: In the internal combustion engine, in the fuel supply passage from the fuel tank to the fuel injection valve, when the fuel pressure in the fuel supply passage exceeds a set pressure, the fuel supplied to the fuel injection valve is passed through the return path. A pressure regulator is provided to return to the fuel tank via
In the fuel concentration learning device, when fuel supply to the fuel tank is detected by the fuel supply detection means, the fuel supply path from the fuel tank is set so that the fuel pressure in the fuel supply path exceeds the set pressure. 2. A fuel circulation control means is provided for driving a fuel pump for discharging the fuel to replace the fuel in the fuel supply path with the fuel in the fuel tank after refueling. A fuel concentration learning device for an internal combustion engine.   The fuel concentration estimating means detects the fuel concentration from the time when fuel supply to the fuel tank is detected by the fuel supply detecting means until the replacement of fuel in the fuel supply path by the fuel circulation control means is completed. The estimation result is corrected so that a change amount from a fuel concentration learning value before refueling becomes smaller as the fuel circulation time is shorter, and is reflected in the fuel concentration learning value. A fuel concentration learning device for an internal combustion engine. The air-fuel ratio of the fuel mixture supplied to the internal combustion engine is detected from the exhaust components of the internal combustion engine that can be operated with the alcohol-mixed fuel, and the fuel supply amount to the internal combustion engine is adjusted so that the air-fuel ratio becomes the target air-fuel ratio. Fuel that is provided in a control device for an internal combustion engine that executes air-fuel ratio control to be corrected, learns the fuel concentration of the fuel supplied to the internal combustion engine from a change in the operating state of the internal combustion engine, and reflects it in the control of the fuel supply amount A concentration learning device,
In the internal combustion engine, in the fuel supply passage from the fuel tank to the fuel injection valve, when the fuel pressure in the fuel supply passage exceeds a set pressure, the fuel supplied to the fuel injection valve is passed through the return path. A pressure regulator is provided to return to the fuel tank via
The fuel concentration learning device
Refueling detection means for detecting that fuel has been supplied to the fuel tank of the internal combustion engine;
A fuel pump for discharging fuel from the fuel tank to the fuel supply path so that the fuel pressure in the fuel supply path exceeds the set pressure when fuel supply to the fuel tank is detected by the fuel supply detection means; Fuel circulation control means for driving and replacing the fuel in the fuel supply path with the fuel in the fuel tank after refueling;
A fuel concentration learning device for an internal combustion engine, comprising:   When fuel supply to the fuel tank is detected by the fuel supply detection means while the operation of the internal combustion engine is stopped, the fuel circulation control means drives the fuel pump to supply fuel in the fuel supply path after refueling. The fuel concentration learning device for an internal combustion engine according to any one of claims 2 to 4, wherein the fuel concentration in the fuel tank is substituted.   The fuel circulation control means drives the fuel pump when fuel supply to the fuel tank is detected by the fuel supply detection means during operation of the internal combustion engine, and supplies fuel in the fuel supply path after fuel supply. 6. The fuel concentration learning device for an internal combustion engine according to claim 5, wherein the fuel in the tank is replaced and the fuel circulation time required for the replacement is increased as compared to when the operation of the internal combustion engine is stopped.   The fuel circulation control means determines whether or not the fuel pump is driven when fuel supply to the fuel tank is detected by the fuel supply detection means. If the fuel pump is not driven, the fuel circulation control means After driving the pump to replace the fuel in the fuel supply path with the fuel in the fuel tank after refueling, the driving of the fuel pump is stopped, and if the fuel pump is driven, the fuel pump The fuel discharge amount from the fuel pump is replaced with the fuel in the fuel tank after refueling, and then the fuel discharge amount from the fuel pump is returned to the original discharge amount. The fuel concentration learning device for an internal combustion engine according to any one of claims 2 to 6, wherein the device is a fuel concentration learning device.   The fuel supply detection means determines that fuel supply to the fuel tank has been made when the amount of fuel in the fuel tank increases more than a predetermined fuel supply determination amount. The fuel concentration learning device for an internal combustion engine according to any one of claims 7 to 9. When refueling to the fuel tank is detected by the refueling detection means, a refueling history indicating that fact is stored, and then the air-fuel ratio control based on the air-fuel ratio control is performed by controlling the fuel supply amount based on the learning result of the fuel concentration. When the deviation from the reference value of the fuel ratio correction amount becomes equal to or less than the set value, the fuel supply history holding means for erasing the storage of the fuel supply history is provided,
The fuel concentration learning device for an internal combustion engine according to any one of claims 1 to 8, wherein the fuel concentration learning is performed when a fuel supply history is stored in the fuel supply history holding unit. The control device is configured to execute purge control for supplying evaporated fuel from the fuel tank to an intake system of an internal combustion engine,
10. The fuel concentration learning device according to claim 1, further comprising purge control prohibiting means for prohibiting execution of the purge control during learning of the fuel concentration. A fuel concentration learning device for an internal combustion engine.

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