JP4409984B2 - Device for judging leakage of evaporated fuel treatment system - Google Patents

Description

  The present invention relates to an apparatus for determining whether or not there is a leak in an evaporated fuel processing system of an internal combustion engine after the internal combustion engine is stopped.

There has been proposed a method for determining whether or not there is a leak in the evaporative fuel processing system of the engine after the internal combustion engine (hereinafter referred to as the engine) is stopped (see, for example, Patent Document 1). According to this method, after the engine is stopped, a differential pressure between the pressure of the evaporated fuel processing system and the atmospheric pressure is detected. It is determined whether there is a leak based on the detected change in the differential pressure.
JP 2003-113743 A

  Leak determination is typically performed by an ECU (electronic control unit). The ECU receives an output from a predetermined sensor and determines whether there is a leak.

  Electric power is required for the operation of the ECU. After stopping the engine, the ECU uses the power from the battery to perform a leak determination. On the other hand, after the engine is stopped, the battery is not charged. If the amount of electricity charged in the battery is small when the engine is stopped, the battery may run out due to the leak determination.

  Therefore, there is a need for a device that can perform a leak determination after stopping the engine without causing the battery to run out.

  According to one aspect of the present invention, a leak determination apparatus includes a fuel tank, an intake port that communicates with the atmosphere, a canister that adsorbs evaporated fuel generated in the fuel tank, the fuel tank, and the canister. A first passage to be connected; a second passage for connecting the canister to the intake system of the internal combustion engine; a vent shut valve for opening and closing the intake port of the canister; and a purge control valve provided in the second passage. The leakage of the evaporative fuel processing system provided is determined. The leak determination apparatus includes a pressure sensor for detecting the pressure of the evaporated fuel processing system and a means for detecting the stop of the internal combustion engine. When it is detected that the internal combustion engine has stopped, the leak determination device closes the evaporated fuel processing system by closing the purge control valve and the vent shut valve. Thereafter, the leak determination device determines whether or not there is a leak in the evaporated fuel processing system based on the pressure detected by the pressure sensor. The leak determination device calculates an amount of electricity charged in a battery of a vehicle equipped with the internal combustion engine, and calculates a time allowed for the leak determination based on the calculated amount of electricity. The leak determination device permits the leak determination if the allowable time is equal to or longer than a predetermined time necessary for the leak determination.

  According to one embodiment of the present invention, the leak determination device measures an elapsed time since the start of the leak determination. If the leak determination is permitted, the leak determination device continues the leak determination until the elapsed time reaches the allowable time.

  According to an embodiment of the present invention, the allowable time is further calculated based on the amount of electricity consumed for leak determination.

  According to one embodiment of the present invention, the amount of electricity charged in the battery includes the amount of power generated by a generator mounted on the vehicle when the internal combustion engine is operating, and the amount of electricity mounted on the vehicle. It is calculated based on the amount of electricity consumed by the load.

  According to the present invention, the leak determination is executed so that the time allowed for the leak determination calculated based on the amount of electricity charged in the battery is not exceeded. Therefore, the leak determination can be performed without causing the battery to run out.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an internal combustion engine and its control device according to an embodiment of the present invention.

  An electronic control unit (hereinafter referred to as “ECU”) 5 includes an input interface 5a that receives data sent from each part of the vehicle, a CPU 5b that executes calculations for controlling each part of the vehicle, and a read-only memory (ROM) ) And a random access memory (RAM) 5c, and an output interface 5d for sending control signals to various parts of the vehicle. The ROM of the memory 5c stores a program for controlling each part of the vehicle and various data. A program for performing leak determination according to the present invention, and data and tables used in executing the program are stored in this ROM. The ROM may be a rewritable ROM such as an EPROM. The RAM is provided with a work area for calculation by the CPU 5b. Data sent from each part of the vehicle and control signals sent to each part of the vehicle are temporarily stored in the RAM.

  The engine 1 is an engine having, for example, four cylinders, and an intake pipe 2 is connected thereto. A throttle valve 3 is arranged on the upstream side of the intake pipe 2, and a throttle valve opening sensor (θTH) 4 connected to the throttle valve 3 outputs an electrical signal corresponding to the opening of the throttle valve 3. Supply to ECU5.

  The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 3, and the valve opening time is controlled by a control signal from the ECU 5. The fuel supply pipe 7 connects the fuel injection valve 6 and the fuel tank 9, and a fuel pump 8 provided in the middle supplies the fuel from the fuel tank 9 to the fuel injection valve 6. A regulator (not shown) is provided between the pump 8 and the fuel injection valve 6 and keeps a differential pressure between the pressure of the air taken in from the intake pipe 2 and the pressure of the fuel supplied through the fuel supply pipe 7 constant. When the fuel pressure is too high, excess fuel is returned to the fuel tank 9 through a return pipe (not shown). Thus, the air taken in through the throttle valve 3 passes through the intake pipe 2 and is mixed with the fuel injected from the fuel injection valve 6 and supplied to the cylinder (not shown) of the engine 1.

  An intake pipe pressure (PB) sensor 13 and an intake temperature (TA) sensor 14 are mounted on the downstream side of the throttle valve 3, detect the intake pipe pressure PB and the intake air temperature TA, respectively, and send them to the ECU 5.

  The engine 1 is provided with a crank angle sensor 17. The crank angle sensor 17 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 5 as the crankshaft (not shown) rotates.

  The CRK signal is a pulse signal output at a predetermined crank angle (for example, 30 degrees). The ECU 5 calculates the rotational speed NE of the engine 1 according to the CRK signal. The TDC signal is a pulse signal output at a crank angle related to the TDC position of a piston (not shown).

  The engine water temperature (TW) sensor 18 is attached to a cylinder peripheral wall (not shown) filled with cooling water in the cylinder block of the engine 1, detects the temperature TW of engine cooling water, and sends it to the ECU 5.

  An exhaust pipe 12 is connected to the engine 1, and exhaust is performed via a three-way catalyst (not shown) that is an exhaust gas purification device provided in the middle of the exhaust pipe 12. The LAF sensor 19 provided upstream of the three-way catalyst is a wide area air-fuel ratio sensor, detects the oxygen concentration in the exhaust gas, that is, the actual air-fuel ratio in a range from lean to rich, and sends it to the ECU 5.

  An alternator (generator) 41 is driven by a V belt from a crank pulley of the engine 1. The power generation amount of the alternator 41 follows the engine speed NE. Electric power from the alternator 41 is supplied to an electric load such as an air conditioner, a headlight, and the ECU 5.

  The battery 42 is connected to the alternator 41 and other electric loads. If the amount of electricity consumed by the electrical load is greater than the amount of power generated by the alternator 41, the battery 42 is discharged to compensate for the shortage. If the amount of power generated by the alternator 41 is greater than the amount of electricity consumed by the electrical load, the battery 42 is charged.

  A sensor 43 that detects the voltage VB of the battery 42 is connected to the battery 42. The detected battery voltage VB is sent to the ECU 5.

  An ignition switch 21 is connected to the ECU 5. A switching signal of the ignition switch 21 is sent to the ECU 5.

  A vehicle speed (VP) sensor 22 and an atmospheric pressure (PA) sensor 23 are connected to the ECU 5 to detect the vehicle speed VP and the atmospheric pressure PA, respectively, and send them to the ECU 5.

  Next, the evaporative fuel processing system will be described. The fuel tank 9 is connected to the canister 33 via the charge passage 31 so that the evaporated fuel from the fuel tank 9 can move to the canister 33. The charge passage 31 is provided with a mechanical two-way valve 35. The two-way valve 35 opens when the tank internal pressure is higher than the atmospheric pressure by a first predetermined pressure (for example, 2.7 kPa) or more, and opens when the tank internal pressure is lower than the canister 33 pressure by a second predetermined pressure or more. A negative pressure valve is provided.

  A bypass passage 31a for bypassing the two-way valve is provided. A bypass valve 36 that is an electromagnetic valve is provided in the bypass passage 31a. The bypass valve 36 is normally in a closed state, and opens according to a control signal from the ECU 5.

  The pressure sensor 15 is provided between the two-way valve 35 and the fuel tank 9, and the detection signal is sent to the ECU 5. The output PTANK of the pressure sensor 15 is equal to the pressure in the fuel tank in a steady state where the pressure in the canister 33 and the fuel tank 9 is stable. On the other hand, the output PTANK of the pressure sensor 15 indicates a pressure different from the actual tank internal pressure when the pressure in the canister 33 or the fuel tank 9 changes. The output of the pressure sensor 15 is hereinafter referred to as “tank pressure PTANK”.

  The canister 33 incorporates activated carbon that adsorbs fuel vapor, and has an inlet (not shown) that communicates with the atmosphere via a passage 37. A vent shut valve 38 is provided in the middle of the passage 37. The vent shut valve 38 is normally in an open state and closes in accordance with a control signal from the ECU 5.

  The canister 33 is connected to the downstream side of the throttle valve 3 in the intake pipe 2 via the purge passage 32. A purge control valve 34 which is an electromagnetic valve is provided in the middle of the purge passage 32, and the fuel adsorbed by the canister 33 is appropriately purged to the intake system of the engine via the purge control valve 34. The purge control valve 34 continuously controls the purge flow rate by changing the on-off duty ratio based on a control signal from the ECU 5.

  According to this embodiment, even when the ignition switch 21 is turned off, electricity is supplied to the ECU 5, the bypass valve 36 and the vent shut valve 38 during the period for performing the leak determination. When the ignition switch 21 is turned off, the purge control valve 34 is not supplied with electricity and maintains the valve closed state.

  Input signals from various sensors are passed to the input interface 5a of the ECU 5. The input interface 5a converts the received analog signal into a digital signal. The CPU 5b processes the converted digital signal, performs an operation according to a program stored in the memory 5c, and generates a control signal to be sent to the actuator of each part of the vehicle. This control signal is sent to the output interface 5d, and the output interface 5d sends control signals to the fuel injection valve 6, the purge control valve 34, the bypass valve 36 and the vent shut valve 38.

  FIG. 2 is a block diagram of an apparatus for determining whether there is a leak in the evaporated fuel processing system 50 according to an embodiment of the present invention. Each functional block is typically realized by a computer program stored in the memory 5c. Alternatively, it may be realized by software, hardware and firmware and any combination thereof.

  In one embodiment of the present invention, first and second leak determinations are performed. The second leak determination detects a hole smaller than the first leak determination (for example, a hole having a diameter of about 0.5 millimeter). In the following description, when it is simply referred to as “leak determination”, it includes the first and second leak determinations.

  While the engine is operating, the charge amount calculation unit 51 calculates the amount of electricity charged in the battery 42 at predetermined time intervals. The allowable time calculation unit 52 receives the amount of electricity stored in the battery 42 calculated by the charge amount calculation unit 51 when the engine is stopped. The allowable time calculation unit 52 calculates a time TBATTOK in which the leak determination is allowed based on the amount of electricity of the battery 42 when the engine is stopped.

The determination permission unit 53 determines whether or not a condition for performing the leak determination is satisfied after the engine is stopped. The allowable time TBATTOK calculated by the allowable time calculation unit 52 is compared with the first determination time TMDDPTL (for example, 300 seconds ). Here, the first determination time TMDDPTL indicates a time required to execute the first leak determination, and is predetermined by, for example, simulation. The determination permitting unit 53 permits the leak determination to be performed when the allowable time TBATTOK is equal to or longer than the first determination time TMDDPTL. If the allowable time TBATTOK is smaller than the first determination time TMDDPTL, the determination permission unit 53 prohibits the leak determination from being performed.

  If the execution of the leak determination is permitted, the leak start unit 54 opens the vent shut valve 38 and the bypass valve 36 to open the evaporated fuel processing system 50 to the atmosphere. The atmosphere release process is executed over a predetermined time. Thereafter, the vent shut valve 38 is closed.

  The leak determination unit 55 starts the first and second leak determinations when the vent shut valve 38 is closed. The first and second leak determinations are executed by the first leak determination unit 61 and the second leak determination unit 62, respectively, at predetermined time intervals.

  The timer 57 measures an elapsed time TEONVTL from the start of the second leak determination. The determination canceling unit 58 compares the allowable time TBATTOK calculated by the allowable time calculating unit 52 with the elapsed time TEONVTL measured by the timer 57. If the elapsed time TEONVTL of the second leak determination reaches the allowable time TBATTOK, the determination canceling unit 58 stops the second leak determination.

  In the first leak determination, a determination result can be obtained within the first determination time TMDDPTL. On the other hand, since the second leak determination detects a smaller hole, it is preferably performed over a longer time than the first leak determination. For example, the second determination time during which the second leak determination is performed is performed over 1000 seconds, which is longer than the first determination time TMDDPTL (eg, 300 seconds). In one embodiment of the present invention, first, if the allowable time TBATTOK is equal to or greater than the first determination time TMDDPTL, the first and second leak determinations are permitted. Further, for the second leak determination, the elapsed time The second leak determination is continued until the allowable time TBATTOK is reached.

  Since the power generation by the alternator 41 is stopped after the engine is stopped, the charging of the battery 42 is stopped. The leak determination is executed by the ECU 5 and consumes the amount of electricity from the battery. If the amount of electricity necessary for executing the leak determination does not remain in the battery, the battery may run out by executing the leak determination.

  According to the present invention, based on the amount of electricity charged in the battery, the time allowed for the leak determination is calculated. The leak determination is performed so as not to exceed the allowable time. Therefore, it is possible to avoid battery exhaustion due to execution of leak determination.

  It should be noted that the method for preventing the determination time for performing the leak determination from exceeding the allowable time can be changed according to how the leak determination is realized. For example, if the time for performing the leak determination can be determined in advance as in the first leak determination, the leak determination is permitted or prohibited by comparing the allowable time with the predetermined time. To do. When it is difficult to predetermine the time for performing the leak judgment as in the second leak judgment, the leak judgment is stopped when the elapsed time from the start of the leak judgment reaches the allowable time. To do. Further, when the minimum determination time necessary for the leak determination can be determined in advance, if the minimum determination time is less than the allowable time, the leak determination is started, and the elapsed time of the leak determination is the allowable time. The leak determination may be continued until the time is reached. In any leak determination, it is an object of the present invention to perform the leak determination so as not to exceed the allowable time calculated based on the amount of electricity of the battery.

  The leak determination can be executed by any known method. According to one embodiment of the present invention, the first determination unit 61 determines whether or not there is a leak in the evaporated fuel processing system 50 based on the twice differential value of the tank internal pressure PTANK. The second determination unit 62 determines whether there is a leak based on the relationship between the tank internal pressure PTANK and the stagnation time of the tank internal pressure PTANK.

  The first leak determination will be described with reference to FIGS.

  FIG. 3 is an example of a time chart showing the transition of the tank internal pressure PTANK. Specifically, FIG. 3 shows the transition of the tank internal pressure PTANK from the time t0 when the vent shut valve 38 is closed after the atmospheric release process. 3A shows a case where the evaporative fuel processing system 50 is normal (that is, there is no leak), and FIG. 3B shows a case where the evaporative fuel processing system 50 has a leak. When the fuel vapor processing system 50 is normal, the tank internal pressure PTANK increases almost linearly. When there is a leak in the evaporated fuel processing system 50, the tank internal pressure PTANK increases at a relatively large rate of change, and then the rate of change gradually decreases. Therefore, it is possible to determine whether or not there is a leak by observing the transition of the change rate of the tank internal pressure PTANK.

  In one embodiment of the present invention, a twice differential value of the tank internal pressure PTANK is used to calculate a determination parameter for determining whether there is a leak. If the evaporative fuel processing system 50 is normal, the twice differential value of the tank internal pressure PTANK is almost zero. If there is a leak in the evaporated fuel processing system 50, the twice differential value becomes a negative value.

  FIG. 4A shows an example of an actual measurement value of the tank internal pressure PTANK sampled at regular intervals. When the tank internal pressure detected in the current sampling cycle is represented by PTANK (k), the tank internal pressure change amount DP is represented by Expression (1).

DP = PTANK (k) −PTANK (k−1) (1)
FIG. 4B is a time chart showing the transition of the change amount DP. It is shown that the change amount DP tends to gradually decrease. In one embodiment of the present invention, a regression line L1 indicating the transition of the change amount DP is obtained by the least square method, and the slope EDPLPLSQA (referred to as a first slope parameter) is calculated. The first slope parameter represents a twice differential value of the tank internal pressure PTANK.

  When the amount of evaporated fuel generated in the fuel tank 9 is large and the rate of change in pressure after closing the vent shut valve 38 is large, the variation DP gradually increases even if the evaporated fuel processing system 50 is normal. It has been experimentally confirmed that it tends to decrease. In order to more accurately determine whether or not there is a leak even in such a state, in one embodiment of the present invention, as shown in FIG. 5, the first determination time from the time t0 when the vent shut valve 38 is closed is shown. The maximum value DPEOMAX of the tank internal pressure during the period until TMDDPTL elapses is detected. If there is a leak in the evaporated fuel processing system 50, the ratio of the slope EDPLSQA with respect to the maximum value DPEOMAX increases. By examining the ratio, it can be determined whether there is a leak. The ratio is calculated by the equation (2), and this is set as a determination parameter EODDPJUD.

EODDPJUD = | EDDPLSQA | / DPEOMAX (2)
FIG. 6 plots data when there is no leak in the evaporated fuel processing system 50 (that is, normal) as a black circle on the coordinate plane with the determination parameter EODDPJUD as the vertical axis and the maximum pressure DPEOMAX as the horizontal axis. Data in some cases are plotted as white circles. As is apparent from this figure, it is possible to accurately determine whether or not there is a leak by setting the threshold value DDPJUD to an appropriate value.

  Next, the second leak determination will be described with reference to FIG. When the evaporative fuel processing system 50 has a small hole (for example, a hole having a diameter of 0.5 millimeter) and the change rate of the tank internal pressure PTANK is very small, it is difficult to detect the leak by the first determination. Sometimes. According to the second determination, a leak due to such a small hole can be detected.

  (A) of FIG. 7 shows the transition of the tank internal pressure PTANK in a normal case (more precisely, as will be described later, the tank internal pressure PTANKAVE obtained by smoothing the tank internal pressure PTANK (applying a low-pass filter)) 7B shows the transition of the tank internal pressure PTANK when there is a leak (more accurately, as will be described later, the tank internal pressure PTANKAVE obtained by smoothing the tank internal pressure PTANK (applying a low-pass filter)). The duration during which the detected pressure PTANK does not change is defined as the stagnation time TSTY. T1, T2, and T3 shown in the figure correspond to the stagnation time TSTY. When the relationship between the stagnation time TSTY and the tank internal pressure PTANK is plotted, a correlation characteristic as shown in FIG. 7C is obtained in the normal case, and in FIG. 7D when there is a leak. Correlation characteristics as shown in FIG. Focusing on the slopes of the regression lines L11 and L12 in each figure, the slope AL11 of the regression line L11 is a relatively small positive value, and the slope AL12 of the regression line L12 is a negative value having a large absolute value. I understand. In one embodiment of the present invention, a leak is determined based on the slope of a regression line (referred to as a second slope parameter EODTMJUD) representing the correlation characteristic between the tank internal pressure PTANK and the stagnation time TSTY.

  FIG. 8 is a flowchart of a process for calculating the time allowed for the leak determination based on the amount of electricity charged in the battery. This process is performed at predetermined time intervals (eg, 80 milliseconds) while the engine is running (ie, from when the ignition key is turned on until it is turned off).

  In step S11, the rotation speed NACG of the alternator 41 is calculated by multiplying the pulley ratio KPULLEY by the detected current engine speed NE. The pulley ratio KPULLEY is a ratio of the diameter of the crank pulley to the diameter of the pulley of the alternator 41. For example, if the ratio of the diameter of the crank pulley to the diameter of the pulley of the alternator 41 is 3: 1, the pulley ratio is 3.

  In step S12, a predetermined map is referred to based on the rotation speed NACG of the alternator and the detected current engine water temperature TW, and a power generation current ACGGENE of the alternator 41 is obtained. The generated current ACGGENE corresponding to the rotational speed NACG of the alternator 41 and the engine coolant temperature TW can be calculated in advance by simulation or the like and defined in the map. The map can be stored in the memory 5c. Typically, the power generation current ACGGENE is set to increase as the rotational speed NACG increases. Further, the generated current ACGGENE decreases as the temperature of the alternator coil increases. Since it is difficult to directly measure the coil temperature, the engine water temperature TW is used. The power generation current ACGGENE is set to be smaller as the engine water temperature TW is higher.

  In step S13, a predetermined map is referred to based on the detected vehicle speed VP, and a current ELLOAD supplied from the battery 42 to the electric load is obtained. An example of the map is shown in FIG.

  Examples of the electric load include a headlight, a small lamp, a stop lamp, and an air conditioner. As the vehicle speed VP decreases, the current ELLOAD supplied to the electric load decreases. This is mainly due to the influence of the fan that cools the stop lamp and the radiator. When the vehicle is stopped or when the brake is depressed to decelerate the vehicle, the stop lamp is lit. As the vehicle speed decreases, the wind that hits the fan becomes weaker, and the fan that cools the radiator needs to be electrically driven.

  In step S14, the current ELLOAD supplied to the electric load is subtracted from the generated current ACGGENE of the alternator 41 to calculate the charging / discharging current BATTCHRGX of the battery 42. The charging / discharging current BATTCHRGX of the battery 42 is expressed as a positive value when the battery 42 is charged, and is expressed as a negative value when the battery 42 is discharged.

  The maximum value of the charge / discharge current of the battery 42 is determined depending on the capacity specific to the battery. In step S15, the charging / discharging current BATTCHRGX of the battery 42 calculated in step S14 is subjected to limit processing based on the maximum charging / discharging current value BATTCHRGH determined according to the capacity of the battery. The maximum value BATTCHRGH has a positive value in the case of a charging current, and a negative value in the case of a discharging current.

  For example, if the charging current BATTCHRGX is larger than the maximum value BATTCHRGH, the maximum value is calculated as the charging / discharging current BATTCHRG. If the charging current BATTCHRGX is smaller than the maximum value BATTCHRGH, the charging current BATTCHRGX is calculated as the charging / discharging current BATTCHRG.

  If the discharge current BATTCHRGX is smaller than the maximum value BATTCHRGH (note that both are represented by negative values), the maximum value is calculated as the charge / discharge current BATTCHRG. If the discharge current BATTCHRGX is larger than the maximum value BATTCHRGH, the discharge current BATTCHRGX is calculated as the charge / discharge current BATTCHRG.

  In step S16, first, the amount of current per second of the charge / discharge current BATTCHRG calculated in step S15 is calculated according to the equation (3).

BATTCHRG x cycle time (seconds) (3)
For example, when the cycle time of the process of this flowchart is 80 milliseconds, the cycle time of Expression (3) is 0.08 seconds.

  The current value of the integrated value of the charge / discharge current of the battery is obtained by adding the charge / discharge current BATCHRG per second calculated by the equation (3) to the previous value BATCGTLX (n-1) of the integrated value of the charge / discharge current of the battery. The value BATCGTLX (n) is calculated. The current value BATCGTLX (n) of the integrated value of the charge / discharge current of the battery represents the amount of electricity currently charged in the battery.

  In step S17, the amount of electricity BATCGTLX (n) currently charged in the battery is subjected to limit processing with a predetermined upper limit value, and the amount of electricity BATCGTL that can be used for leak determination is calculated. It is known that when the discharge current exceeds 3 to 5% with respect to the total capacity of the battery, the battery rapidly deteriorates. Therefore, for example, (total battery capacity × 0.03) is set to the upper limit value, and if the electric quantity BATCGTLX (n) exceeds the upper limit value, the upper limit value is set to the electric quantity BATCGTL. If the electric quantity BATCGTLX (n) is less than or equal to the upper limit value, the electric quantity BATCGTLX (n) is set to the electric quantity BATCGTL.

  In step S18, it is determined whether or not the amount of electricity BATCGTL of the battery 42 that can be used for the leak determination calculated in step S17 is greater than zero. If the amount of electricity BATCGLT is equal to or less than zero, it indicates that the amount of electricity that can be used for the leak determination does not remain in the battery 42. Therefore, zero is set as the leak determination allowable time TBATTOK (S19). If the amount of electricity BATCGTL is greater than zero, the amount of electricity BATCGLL is divided by the current BATTDISIONV required for leak determination to calculate a leak determination allowable time TBATTOK (S20). The current BATTDISIONV required for leak determination is calculated in advance by simulation or the like.

  As an example, FIG. 10 shows how the leak determination allowable time TBATTOK changes according to the change in the vehicle speed VP. As the vehicle speed VP increases, the amount of electricity consumed by the electrical load decreases, and thus the amount of electricity charged in the battery 42 increases. As a result, the allowable time TBATTOK increases as the vehicle speed VP increases. Every time the vehicle speed VP is zero, that is, the brake is applied, electricity is consumed by the stop lamp, and thus the allowable time TBATTOK is shortened.

  FIG. 11 is a flowchart of a process for determining whether a condition for executing the leak determination is satisfied. In this process, the permission flag FMCNDEONV is set to a value of 1 in response to the condition being satisfied. This process is performed every predetermined time (for example, 80 milliseconds).

  In step S31, the value of the permission flag FMCNDEONV is checked. If FMCNDEONV = 0, the value of the permission flag FMCNDEONV is maintained at zero (S32), and this process ends.

  In step S33, the value of the determination end flag FDONE that is set to 1 when the leak determination ends is checked. If FDONE = 1, since the leak determination has already been completed, the process proceeds to step S32.

  If FDONE = 0, it is checked in step S34 whether the engine is stopped, that is, whether the ignition switch 21 is turned off. When the engine is in operation, the value of the permission flag FMCNDEONV is set to zero (S32), and this process is terminated.

  When the engine is stopped, the process proceeds to step S35, and a refueling flag FREFUEDC, which is set to a value 1 when refueling, is checked. When the fuel is being supplied, the leak determination cannot be executed accurately, and the process proceeds to step S32.

  In step S36, the leak determination allowable time TBATTOK calculated in FIG. 10 is compared with the first determination time TMDDPTL required for the leak determination. The first determination time TMDDPTL is determined in advance and stored in the memory. If the allowable time TBATTOK is smaller than the first determination time TMDDPTL, it indicates that the amount of electricity necessary for executing the first leak determination is not left in the battery. If the first leak determination is performed in such a state, there is a risk that the battery will run out, so the process proceeds to step S32 and the value of the permission flag FMCNDEONV is set to zero (S32).

  If the allowable time TBATTOK is equal to or longer than the first determination time TMDDPTL, it indicates that the amount of electricity necessary for executing the leak determination is left in the battery 42. Proceeding to step S37, the permission flag FMCNDEONV is set to a value of 1, and execution of leak determination is permitted.

  In this embodiment, in order to perform the leak determination, the detected tank internal pressure PTANK is smoothed (a low-pass filter is applied), the tank internal pressure PEONVAVE, and the stagnation indicating the value when the tank internal pressure PEONVAVE is stagnant Tank internal pressure PEOAVDTM is used.

  FIG. 12 shows a flowchart of a process for calculating the tank internal pressure PEONVAVE and the stagnation tank internal pressure PEOAVDTM. This process is executed every predetermined time (for example, 80 milliseconds) after the engine is stopped.

  In step S52, if the value of the permission flag FMCNDEONV is zero, it indicates that the condition for executing the leak determination is not satisfied. If the execution condition for the leak determination is not satisfied, the downcount timer TEODLY is set to a predetermined time TEODLY0 (for example, 90 seconds) and started (S53). The timer TEODLY is a timer that measures the atmosphere release processing period.

  In step S54, the execution flag FEONVEXE is set to zero. Further, the bypass valve 36 and the vent shut valve 38 are maintained in the open state, and the evaporated fuel processing system 50 is opened to the atmosphere. The flag FVSVCPCTL is set to zero to indicate that the vent shut valve 38 is open.

  If FMCNDEONV = 1 in step S52, it indicates that the condition for executing the leak determination is satisfied. In step S55, it is determined whether or not the value of the execution flag FEONVEXE is 1. When this step is executed for the first time, the answer is No. Therefore, the process proceeds to step S56, and it is determined whether the value of the timer TEODLY started in step S53 is zero. When this step is executed for the first time, the answer is No, so the flag FVSVCPTCL is set to zero (S61), and the vent shut valve 38 is maintained in the open state.

  If TEODLY = 0 in step S56, the process proceeds to step S57, and the current tank internal pressure PTANK is stored as the start pressure PEOTANK0. This tank internal pressure PTANK shows almost atmospheric pressure by the atmospheric release process.

  In step S58, the corrected tank internal pressure PEOTANK, the tank internal pressure PEONVAVE, the comparison parameter current value PEODTM, the comparison parameter previous value PEODTMZ, the stagnation tank internal pressure current value PEOAVDTM, and the stagnation tank internal pressure previous value PEOAVDTMZ are set to zero.

  In step S59, the execution flag FEONVEXE is set to a value of 1, and execution of leak determination is started. In step S60, the downcount timer TEODTM is set to a predetermined time TMEODTM and started. Further, the upcount timer TEONVTL is set to zero, and the process proceeds to step S61. The timer TEONVTL is a timer that measures an elapsed time since the start of the leak determination.

  If this routine is entered after the execution flag FEONVEXE is set to the value 1 in step S59, the answer to step S55 is Yes. In step S62, the corrected tank internal pressure PEOTANK is calculated by subtracting the start pressure PEOTANK0 from the current tank internal pressure PTANK. In step S63, the tank internal pressure PEONVAVE is calculated from the equation (4).

Current value of PEONVAVE = CPTAVE x PEOTANK
+ (1-CTPAVE) x previous value of PEONVAVE (4)
Here, CPTAVE is a smoothing (smoothing) coefficient set to a value between zero and one.

  In step S64, the current value PEODTM is set to the previous value PEODTMZ of the comparison parameter. In step S65, the tank internal pressure PEONVAVE is set to the current value PEODTM of the comparison parameter. In step S66, it is determined whether the current value of the comparison parameter is equal to the previous value. If this answer is No, it indicates that the tank internal pressure PEONVAVE is changing. In step S67, the downcount timer TEODTM is set to a predetermined time TMEODTM and started. In step S71, the flag FVSVCPTCL is set to 1 and the vent shut valve 38 is closed.

  If the answer to step S66 is Yes, it indicates that the tank internal pressure PEONVAVE is stagnant. In step S68, it is determined whether or not the value of the timer TEODTM is zero. When this step is executed for the first time, the answer is No, so the process proceeds to step S71. If the answer to step S68 is Yes, the current value PEOAVDTM is set to the previous value PEOAVDTMZ of the stagnation tank internal pressure (S69), and the tank internal pressure PEONVAVE is set to the current value PEOAVDTM (S70). Thereafter, the process proceeds to step S71.

  As described above, when the execution condition for leak determination is satisfied, the atmosphere release process is executed (S54), and then the vent shut valve 38 is closed (S71). While the leak determination is being executed, the calculation of the tank internal pressure PEONVAVE and the stagnant tank internal pressure PEOAVDTM is executed.

  13 and 14 are flowcharts of the first leak determination process. This process is executed every predetermined time (for example, 1 second).

  In step S80, the value of the flag FVSVCPTCL is checked. As described above, the flag has a value of 1 when the vent shut valve 38 is closed. If FVSVCPTCL = 0, the current tank internal pressure PEONVAVE is set to the initial pressure PEONVAV (S81). In step S82, various parameters used for calculation of the first slope parameter EDPLPLSQA are initialized. The first slope parameter EDPLPLSQA indicates the slope of the regression line L1 described with reference to FIG.

  In step S83, the maximum pressure DPEOMAX is set to zero. In step S84, the first leakage determination flag FDDPLK, the hold flag FDDPJDHD, and the first determination end flag FEONVDDPJUD are all set to zero. The first leak determination flag FDDPLK is a flag that is set to a value of 1 when it is determined that there is a leak. In step S85, the value of the upcount timer TDDPTL is set to zero.

  If FVSVCPTCL = 1 in step S80, the vent shut valve 38 is closed. In step S86, it is determined whether the value of the timer TDDPTL is equal to or longer than the first determination time TMDDDPTL. As described above, the first determination time TMDDPTL is a time necessary for the first leak determination. When this step is executed for the first time, the answer is No, so steps S87 to S95 are executed to calculate the first slope parameter EDPLPLSQA and the maximum pressure DPEOMAX.

  In step S87, the time parameter CEDDPCAL is incremented by one. In Step S88, the pressure change amount DPEONV is calculated by subtracting the initial pressure PEONVAVO from the tank internal pressure PEONVAVE.

  In step 89, the integrated value ESIGMAX of the time parameter CEDDPCAL is calculated by equation (5).

Current value of ESIGMAX = previous value of ESIGMAX + CEDDPCAL (5)
In step S90, an integrated value ESIGMAX2 of a value obtained by squaring the time parameter CEDDPCAL is calculated by the equation (6).

Current value of ESIGMAX2 = previous value of ESIGMAX2 + CEDDPCAL x CEDDPCAL (6)
In step S91, an integrated value ESIGMAXY of the product of the time parameter CEDDPCAL and the pressure change amount DPEONV is calculated by the equation (7).

Current value of ESIGMAXY = previous value of ESIGMAXY + CEDDPCAL x DPEONV (7)
In step S92, the integrated value ESIGMAY of the pressure change amount DPEONV is calculated by the equation (8).

Current value of ESIGMAY = previous value of ESIGMAY + DPEONV (8)
In step S93, using the time parameter CEDDPCAL, integrated values ESIGMAX, ESIGMAX2, ESIGMAXY, and ESIGMAY calculated in steps S87 and S89 to S92, a first slope parameter EDPLSQA is calculated according to equation (9).

  In step S94, the current tank internal pressure PEONVAVE is set to the initial pressure PEONVAVO. In step S95, the larger one of the maximum pressure DPEOMAX and the tank internal pressure PEONVAVE is selected to determine the maximum pressure DPEOMAX.

  When the value of the timer TDDPTL reaches the first determination time TMDDPTL in step S86, the process proceeds to step S101 (FIG. 14), and it is determined whether or not the maximum pressure DPEOMAX is equal to or higher than the predetermined pressure PDDPMIN. If the answer is No, it indicates that the increase of the tank internal pressure PTANK is insufficient. In this case, since accurate determination cannot be made, the first determination end flag FEONVDDPJUD is set to zero (S112).

  If DPEOMAX ≧ PDDPMIN in step S101, the determination parameter EODDPJUD is calculated by the above-described equation (2) (S102).

  In step S103, the correction coefficient KEOP1JDX is calculated with reference to the KEOP1JDX table shown in FIG. 15 based on the atmospheric pressure PA. The KEOP1JDX table is set so that the correction coefficient KEOP1JDX decreases as the atmospheric pressure PA decreases. PA1, PA2, and PA3 in the figure are set to, for example, 77 kPa (580 mmHg), 84 kPa (630 mmHg), and 99 kPa (740 mmHg), and KX1 and KX2 are set to, for example, 0.75 and 0.84, respectively.

  In steps S104 and S105, the OK determination threshold value DDPJUDOK and the NG determination threshold value DDPJUDNG are calculated according to the equations (10) and (11) using the correction coefficient KEOP1JDX.

DDPJUDOK = EODDPJDOK × KEOP1JDX (10)
DDPJUDNG = EODDPJDNG × KEOP1JDX (11)
Here, EODDPJDOK and EODDPJDNG are a threshold value for OK determination and a predetermined threshold value for NG determination, respectively, and the former is set to a value smaller than the latter.

  In step S106, it is determined whether the determination parameter EODDPJUD is equal to or less than an OK determination threshold value DDPJUDOK. If the answer is Yes, it is determined that the evaporated fuel processing system 50 is normal, and the first leak determination flag FDDPLK is set to zero (S108).

  If EODDPJUD> DDPJUDOK in step S106, it is determined whether or not the determination parameter is greater than the threshold value DDPJUDNG for determining ODDPJUDD (S107). If this answer is Yes, it is determined that there is a leak in the evaporated fuel processing system 50, and the first leak determination flag FDDPLK is set to a value 1 (S109). If the answer to step S107 is No, that is, if DDPJUDOK <EODDPJUD ≦ DDPJUDNG, the determination is suspended and the suspension flag FDDPJDHD is set to a value 1 (S110).

  In step S111, the first determination end flag FEONVDDPJUD is set to 1 to indicate that the first determination has ended.

  According to the first determination method, the first slope parameter EDPLSQA corresponding to the twice differential value with respect to the time of the tank internal pressure PEONVAVE is calculated. Further, the determination parameter EODDJUD is calculated by dividing the first inclination parameter EDPLPLSQA by the maximum pressure DPEOMAX. If the determination parameter is equal to or less than the OK determination threshold value DDPJUDOK, the evaporated fuel processing system 50 is determined to be normal, and if it is greater than the NG determination threshold value DDPJUDNG, it is determined that there is a leak. Thus, the first determination described with reference to FIG. 6 is realized.

FIG. 16 is a flowchart of a process for determining whether or not the execution condition for the second leak determination is satisfied. This process is performed every predetermined time (for example, 1 second) after the engine is stopped.

  In step S121, the value of the flag FVSVCPTCL that is set to 1 when the vent shut valve 38 is closed is checked. If FVSVCPTCL = 0, the process proceeds to step S125, the permission flag FEODTMEX is set to zero, and the execution of the second leak determination is prohibited.

  If FVSVCPTCL = 1 in step S121, the process proceeds to step S122, and it is determined whether or not the value of the upcount timer TEONVTL is smaller than the leak determination allowable time TBATTOK calculated in step S20 of FIG. The upcount timer TEONVTL is activated when the execution flag FEONVEXE is set to a value 1 (S60 in FIG. 12), and measures the elapsed time since the execution of the leak determination is started.

  If TEONVTL ≧ TBATTOK, it indicates that the elapsed time from the start of the execution of the second leak determination exceeds the allowable time based on the amount of electricity charged in the battery. If the second leak determination is further continued, there is a risk that the battery will run out. Accordingly, the process proceeds to step S124, where the stop flag FEONVTMUP is set to the value 1 and the second leak determination is stopped. Since the second leak determination is stopped, zero is set to the permission flag FEODTMEX in step S125.

  If TEONVTL <TBATTOK in step S122, the maximum execution time TMEOMAX (which is a predetermined value, for example, 2400 seconds) is compared with the elapsed time TEONVTL in step S123. If TEONVTL ≧ TMEOOMAX, it indicates that the maximum execution time during which the second leak determination can be executed has elapsed. Proceeding to step S124, the cancel flag FEONVTMUP is set to 1 and the second determination is cancelled. Since the second leak determination is stopped, zero is set to the permission flag FEODTMEX in step S125.

  If TEONVTL <TMEOOMAX in step S123, the process proceeds to step S126, and it is determined whether or not the current value PEOAVDTM of the stagnation tank internal pressure is not less than the first predetermined pressure P0 and not more than the second predetermined pressure P1. For example, the first predetermined pressure P0 is set to a value equal to the atmospheric pressure, and the second predetermined pressure P1 is slightly higher than the first predetermined pressure P0, for example, 0.133 kPa ( 1 mmHg) is set to a high value.

  If the answer to step S126 is Yes, it indicates that the current value PEOAVDTM of the stagnation tank internal pressure is near atmospheric pressure. In step S130, it is determined whether or not the previous value PEOAVDTMZ of the stagnation tank internal pressure is lower than the first predetermined pressure P0. If PEOAVDTMZ <P0, it indicates that the stagnation tank internal pressure is increasing. In step S132, the permission flag FEODTMEX is set to zero.

  On the other hand, if PEOAVTMZ ≧ P0 in step S130, it indicates that the stagnation tank internal pressure is stagnating or decreasing. In step S131, the permission flag FEODMEX is set to a value 1.

  If the answer to step S126 is No, that is, if PEOAVDTM <P0 or PEOAVDTM> P1, it is determined whether the current value PEOAVDTM of the stagnation tank internal pressure is equal to the previous value PEOAVDTMZ (S127). If they are equal, it indicates that the stagnation tank internal pressure has not changed, and the process ends.

  If the answer to step S127 is No, it is determined whether or not the current value PEOAVDTM of the stagnation tank internal pressure is greater than the previous value PEOAVDTMZ (S128). If this answer is Yes, it indicates that the stagnation tank internal pressure has increased, and the permission flag FEODTMEX is set to zero (S132).

  If the answer to step S128 is No, it indicates that the stagnation tank internal pressure has decreased, the process proceeds to step S129, and the permission flag FEODTMEX is set to a value 1.

  Thus, the permission flag FEODTMEX is set to zero when the stagnation tank internal pressure PEOAVDTM is increasing, and is set to 1 when it is decreasing. Further, when the stagnation tank internal pressure is stagnating in the vicinity of atmospheric pressure (between P0 and P1), the permission flag FEODTMEX is always set to 1.

  Thus, the second leak determination is executed when the stagnation tank internal pressure is stagnating in the vicinity of the atmospheric pressure and when it is decreasing.

  17 and 18 are flowcharts of a process for executing the second leak determination. This process is executed every predetermined time (for example, 1 second).

  In step S141, a flag FVSVCPTCL that is set to 1 when the vent shut valve 38 is closed is checked. If FVSVCPTCL = 0, the process proceeds to step S145 (FIG. 18), and the current value DPEOMIN and the previous value DPEOMINZ of the minimum pressure are set to the current stagnation tank internal pressure PEOAVDTM. In step S146, the value of the upcount timer TDTMSTY that measures the stagnation time of the tank internal pressure is set to zero.

  In step S147, various parameters for calculating the second slope parameter EODTMJUD corresponding to the slopes of the regression lines L11 and L12 shown in FIGS. 7C and 7D are initialized.

  In step S148, the second leakage determination flag FDTMLK, the determination impossible flag FDTMDISBL, the second determination end flag FEONVDTMJUD, and the pressure change flag FCHG are all set to zero. The second leak determination flag FDTLK is a flag that is set to a value of 1 when it is determined that there is a leak.

  If the answer to step S141 is Yes, it indicates that the vent shut valve 38 is closed. In step S142, it is checked whether or not the value of the cancel flag FEONVTMUP is 1. If this answer is Yes, the determination impossible flag FDTMDISBL is set to 1 (S143), and the process is terminated.

  If FEONVTMUP = 0 in step S142, the process proceeds to step S144 to check whether the value of the permission flag FEODTMEX is 1. If the answer is No, the process proceeds to step S145, and the execution of the second leak determination is prohibited.

  If FEODTMEX = 1 in step S144, the process proceeds to step S149, and the current value DPEOMIN is set to the previous value DPEOMINZ of the minimum pressure. In step S150, the smaller one of the minimum pressure DPEOMIN and the stagnation tank internal pressure PEOAVDTM is selected and set to the minimum pressure DPEOMIN.

  In step S151, it is determined whether or not the current value DPEOMIN of the minimum pressure is equal to the previous value DPEOMINZ. If this answer is Yes, it is determined whether or not the value of the timer TDTMSTY is equal to or greater than a predetermined value TDTMLK (S152). When this step is executed for the first time, the answer is No. Therefore, the process proceeds to step S153, and the stagnation time parameter CTMSTY is incremented by one. The stagnation time parameter CTMSTY is a parameter corresponding to the stagnation time TSTY (FIG. 7). In step S154, it is determined whether or not the pressure change flag FCHG is 1. When this step is executed for the first time, the answer is No, and the process proceeds to step S164 (FIG. 18).

  When the minimum pressure DPEOMIN changes, that is, when the stagnation tank internal pressure PEOAVDTM decreases, the process proceeds from step S151 to step S159, and the pressure change flag FCHG is set to the value 1. In step S160, the pressure parameter CDTMPCHG is incremented by one. The pressure parameter CDTMTCHHG is a parameter corresponding to the tank internal pressure PTANK shown on the horizontal axis of FIG. 7C or FIG. 7D, and the pressure parameter CDTMPCHG increases as the tank internal pressure PTANK decreases. Therefore, the second inclination parameter EODTMJUD has a negative value corresponding to the straight line L11 in FIG. 7C and a positive value corresponding to the straight line L12 in FIG. 7D.

  In step S161, the integrated value DTMISGX of the pressure parameter CDTMPCHG is calculated from the equation (12).

Current value of DTSIGX = previous value of DTSIGX + CDTMTCHG
(12)
In step S162, the integrated value DTMISGX2 of the value obtained by squaring the pressure parameter CDTMPCHG is calculated by the equation (13).

Current value of DTSIGX2 = previous value of DTSIGX2
+ CDTMPCHG × CDTMPCHG (13)
In step S163, the value of the timer TDTMSTY is returned to zero, and the process proceeds to step S164.

After the pressure change flag FCHG is set to the value 1, the answer to step S151 is Yes, and the process proceeds to step S154 via step S153. Since the answer to step S154 is Yes, the process proceeds to step S155, and the current value of DTMSIGY for calculating the integrated value DTMSIGY of the stagnation time parameter CTMSTY is calculated by the equation (14) = the previous value of DTMSIGY + CTMSTY (14)
In step S156, an integrated value DTMSIGXY of the product of the pressure parameter CDTMPCHG and the stagnation time parameter CTMSTY is calculated by the equation (15).

Current value of DTMSIGXY = previous value of DTMSIGXY +
CDTMPCHG × CTMSTY (15)
In step S157, the pressure change flag FCHG is returned to zero, and the stagnation time parameter CTMSTY is returned to zero. Thereafter, the process proceeds to step S164.

In step S164, it is determined whether or not the pressure parameter CDTMPCHG is greater than one. When the answer is No, the slope of the regression line cannot be obtained and the process is terminated. If CDTMPCHG> 1, then the second gradient parameter EODTMJUD is calculated according to the equation (16) using the pressure parameter CDTMPCHG, the integrated values DTMSIGX, DTSIGX2, DTMSIGY, and DTMSIGXY (S165). In this embodiment, it should be noted that the pressure parameter CDTMPCHG is also a parameter indicating the number of sampling data because the pressure parameter CDTMPCHG is incremented by 1 each time the minimum pressure DPEOMIN changes.

  In step S166, it is determined whether the second slope parameter EODTMJUD is larger than the determination threshold value EODTMJDOK. If the answer is Yes, it is determined that there is a leak, and the second leak determination flag FDTLK is set to a value of 1. The second determination end flag FEONVDTMJUD is set to a value 1 (S169), indicating that the second leak determination has ended.

  If the second slope parameter EODTMJUD is less than or equal to the determination threshold value EODTMJDOK, it is determined whether or not the pressure parameter CDTMPCHG is greater than or equal to a predetermined value DTENBIT (S167). If CDTMPCHG <DTMENBIT, the process ends. When the pressure parameter CDTMPCHG reaches the predetermined value DTENBIT, the process proceeds to step S168, where the second leak determination flag FDTLK is set to zero, indicating that no leak has been detected in the second leak determination. Further, the second determination end flag FEONVDTMJUD is set to a value 1 (S168).

  In step S152, when the value of the timer TDTMSTY for measuring the stagnation time is equal to or greater than the predetermined time TDTMLK, it is determined that there is a leak, the second leak determination flag FDTLK is set to 1, and the second determination The end flag FEONVDTMJUD is set to a value 1 (S158).

  Thus, the second leak determination is executed when the stagnation tank internal pressure PEOAVDTM is stagnating or decreasing. If the stagnation time TDTMSTY is equal to or longer than the predetermined time TDTMLK, or if the second slope parameter EODTMJUD corresponding to the slope of the regression line shown in FIG. It is determined that there is a leak.

  FIG. 19 is a flowchart of a process for performing the final determination. This process is executed every predetermined time (for example, 1 second).

  In step S171, it is determined whether the determination end flag FDONE is 1. If the answer is yes, the process ends. If FDONE = 0, it is determined whether the permission flag FMCNDEONV is 1 (S172). If this answer is Yes, it is determined whether or not the determination impossible flag FDTMDISBL is 1 (S173). If FMCNDEONV = 0 or FDTMDISBL = 1, in order to interrupt the leak determination, the interrupt flag FEONVABOT and the determination end flag FDONE are set to 1 (S174), and this process ends.

  If FDTMDISBL = 0 in step S173, it is determined whether or not the first determination end flag FEONVDDPJUD is 1. If FEONVDDPJUD = 1, the first leak determination is complete. In step S176, it is determined whether or not the value of the hold flag FDDPJDHD is 1. If FDDPJDHD = 1, the interruption flag FEONVABOT is set to zero, and the end flag FDONE is set to 1 (S184).

  If the hold flag FDDPJDHD is zero in step S176, the process proceeds to step S177, and it is determined whether or not the first leak determination flag FDDPLK is 1. If FDDPLK = 1, the failure flag FFSD is set to 1 (S178), indicating that a failure has occurred. If FDDPLK = 0, the normal flag FOK is set to 1 (S179). Thereafter, the process proceeds to step S184.

  If the first leak determination is not completed in step S175, the process proceeds to step S180 to determine whether the second determination end flag FEONVDTMJUD is 1. If the answer is no, the process ends. When the second determination is completed, the process proceeds to S181, and it is determined whether or not the second leakage determination flag FDTLK is 1. If FDTLK = 1, the failure flag FFSD is set to 1 (S182), indicating that a failure has occurred. If FDTLKLK = 0, the normal flag FFSD is set to 1 (S183). Thereafter, the process proceeds to step S184.

  In this way, when one of the first leak determination and the second leak determination ends, the leak determination of the fuel generation processing system ends. Since the second leak determination takes longer than the first leak determination, the result of the first leak determination is preferentially used. Alternatively, the leak determination of the evaporated fuel processing system may be terminated in response to obtaining both determination results. Further, the result of the second leak determination may be obtained only when it is determined that there is a leak in the first leak determination.

  Alternatively, the detected tank pressure PTANK may be used instead of the smoothed tank pressure PEONVAVE and the stagnant tank pressure PEOAVDTM.

  In the processes of FIGS. 17 and 18, the second slope EODTMJUD is calculated by applying the least square method to the pressure parameter CDTMTCHHG and the stagnation time parameter CTMSTY. Alternatively, the second slope EODTMJUD may be calculated by applying the least square method to the values of the tank internal pressure PTANK and the upcount timer TDTMSTY.

  The present invention is applicable to general-purpose internal combustion engines (for example, outboard motors).

1 schematically shows an internal combustion engine and a control device therefor according to one embodiment of the present invention. FIG. The functional block diagram of the leak determination apparatus according to one Example of this invention. The figure which shows transition of the tank internal pressure when performing the leak determination according to one Example of this invention. The figure which shows the regression line calculated based on the time chart which shows the actual measurement data of the tank internal pressure according to one Example of this invention, and this actual measurement data. The figure for demonstrating the maximum pressure in the period which performs the leak determination according to one Example of this invention. The figure for demonstrating the 1st leak determination method according to one Example of this invention. The figure for demonstrating the 2nd leak determination method according to one Example of this invention. The flowchart of the process which calculates the allowable time of the leak determination according to one Example of this invention. The map which shows the relationship between the electric current supplied to an electric load, and a vehicle speed according to one Example of this invention. The time chart which shows an example of the calculated allowable time according to one Example of this invention. The flowchart of the process which judges whether the conditions which perform leak determination are satisfied according to one Example of this invention. 5 is a flowchart of a process for calculating a pressure parameter according to an embodiment of the present invention. 4 is a flowchart of a process for performing a first leak determination according to one embodiment of the present invention. 4 is a flowchart of a process for performing a first leak determination according to one embodiment of the present invention. The figure which shows an example of the table used by FIG. 14 according to one Example of this invention. The flowchart of the process which judges whether the conditions for performing 2nd leak determination are satisfied according to one Example of this invention. 4 is a flowchart of a process for performing a second leak determination according to an embodiment of the present invention. 4 is a flowchart of a process for performing a second leak determination according to an embodiment of the present invention. 4 is a flowchart of a process for performing a final determination according to one embodiment of the present invention.

Explanation of symbols

1 Engine 5 ECU
6 Fuel injection valve 9 Fuel tank
34 Purge control valve 36 Bypass valve 38 Vent shut valve
41 Alternator 42 Battery

Claims (2)

A fuel tank, an intake port that communicates with the atmosphere, a canister that absorbs evaporated fuel generated in the fuel tank, a first passage that connects the fuel tank and the canister, and the canister are connected to the internal combustion engine An apparatus for determining a leak in an evaporated fuel processing system comprising a second passage connected to an intake system, a vent shut valve that opens and closes an intake port of a canister, and a purge control valve provided in the second passage. ,
A pressure sensor for detecting the pressure of the evaporated fuel processing system;
Engine stop detection means for detecting the stop of the internal combustion engine;
If the stop of the internal combustion engine is detected, the evaporated fuel processing system is closed by closing the purge control valve and the vent shut valve, and the evaporated fuel processing system is based on the pressure detected by the pressure sensor. Leak determination means for performing a first leak determination for determining whether or not there is a leak, and a second leak determination for determining a leak smaller than a leak that can be determined by the first leak determination, A leak determination means in which a first determination time required from the start to completion of the first leak determination is predetermined;
An electric quantity calculating means for calculating an electric quantity charged in a battery of a vehicle equipped with the internal combustion engine;
An allowable time calculation means for calculating a time allowed for the leak determination means based on the calculated amount of electricity and the current required for the first and second leak determination ;
If the allowable time is equal to or longer than the first determination time, permission means for permitting the leak determination means to start the first leak determination and the second leak determination;
Means for starting the first and second leak determination in response to the start of the first and second leak determination being permitted;
First time measuring means for measuring a first elapsed time from the start of the first leak determination;
And a second time measuring means for measuring a second elapsed time from the second to leak determination is started,
The leak determination means terminates the first leak determination together with acquisition of the leak determination result when the first elapsed time reaches the first determination time, and the second leak The determination ends when the determination result of the small leak is obtained,
The leak determination means further stops the second leak determination if the second elapsed time reaches the allowable time before the end of the second leak determination.
Leak determination device.   The electric quantity calculation means is further based on an electric power generation amount of a generator mounted on the vehicle and an electric amount consumed by an electric load mounted on the vehicle when the internal combustion engine is operating. The leak determination apparatus according to claim 1, wherein the amount of electricity charged in the battery is calculated.

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