JP2014227907A - Evaporation fuel processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diagnose leakage of an evaporation fuel sealed system at high precision.SOLUTION: An evaporation fuel processing device 11 is provided with a diagnosis part 53 for diagnosing leakage of an evaporation fuel sealed system. The diagnosis part 53 executes leakage diagnosis using a double differential method on the basis of a correlation parameter relating to a double differential value of tank internal pressure Ptank by a tank internal pressure detection part 27 while an atmospheric on-off valve 29 is under a sealed state after an ignition switch 43 is turned off, and leakage diagnosis using a delay time method based on a relationship between the tank internal pressure Ptank and a delay time of the tank internal pressure Ptank by the tank internal pressure sensor 27. The diagnosis 53 preferentially uses leakage diagnosis results using the delay time method (DTM method) for leakage diagnosis results using the double differential method (DDP method).

Description

  The present invention relates to an evaporated fuel processing apparatus for processing evaporated fuel.

  For example, in a vehicle equipped with an internal combustion engine, when the fuel tank is refueled, the occupied volume of the liquid fuel stored in the internal space of the fuel tank increases. As a result, the occupied volume of the gas phase region in the internal space is relatively reduced, and the pressure in the gas phase region (hereinafter referred to as “tank internal pressure”) becomes higher than the atmospheric pressure. Then, the vaporized fuel in the gas phase region staying in the fuel tank tends to come out into the atmosphere. If evaporative fuel is released into the atmosphere, it will contaminate the atmosphere (global environment).

  Therefore, in order to prevent atmospheric (global environment) pollution caused by the emission of evaporated fuel into the atmosphere, the conventional evaporated fuel processing apparatus temporarily adsorbs evaporated fuel in the communication path between the fuel tank and the atmosphere. A canister having an adsorbent is provided, and the tank internal pressure is kept low by adsorbing evaporated fuel to the adsorbent of the canister.

  For example, Patent Document 1 discloses a fuel tank, a canister, a charge passage that communicates between the fuel tank and the canister, an air passage that communicates between the canister and the atmosphere, and a vent shut valve for opening and closing the air passage (at the time of refueling or Evaporative fuel processing apparatus comprising: a purge passage that opens between the canister and the internal combustion engine, and a purge control valve that opens and closes the purge passage (opens during purge execution). Is disclosed.

  In the evaporative fuel processing apparatus according to Patent Document 1, after the internal combustion engine is stopped, a first determination method based on a parameter corresponding to the second derivative value of the fuel tank internal pressure, and a second determination based on the stagnation time of the fuel tank internal pressure. The leak diagnosis of the evaporative fuel sealing system including the fuel tank is performed selectively. Specifically, when the amount of evaporated fuel generated in the fuel tank is relatively large, the diagnosis result by the first determination method is selected, and when the amount of evaporated fuel generation is relatively small, the diagnosis by the second determination method is selected. The result is selected.

  According to the evaporated fuel processing apparatus according to Patent Document 1, it is possible to accurately perform a leak diagnosis of the evaporated fuel processing apparatus with a relatively simple configuration while the internal combustion engine is stopped.

JP 2006-77595 A (paragraph numbers 0028 to 0030)

  By the way, both of the leak diagnosis principles according to the first and second determination methods used in the evaporated fuel processing apparatus according to Patent Document 1 are based on the assumption that the environmental temperature related to the fuel tank changes. The change in the internal pressure of the tank that changes over time in the process of liquidization (or liquefaction) of the liquid fuel sealed in the internal space of the fuel tank in accordance with the environmental temperature change is This is based on correlation with the presence or absence of leakage in the closed system.

  In short, in order to perform leak diagnosis accurately in a short time in the evaporated fuel processing apparatus according to Patent Document 1, it is preferable that the environmental temperature related to the fuel tank dynamically changes from moment to moment.

  Thus, for example, when the evaporative fuel treatment device according to Patent Document 1 is applied to a hybrid vehicle that includes an internal combustion engine and an electric motor as power sources and in which the main heat source, the internal combustion engine, operates only intermittently, In the case where the operating frequency of the fuel tank is low, the change range (dynamic range) of the environmental temperature related to the fuel tank is relatively small as compared with an existing vehicle in which only the internal combustion engine is mounted as a power source. As a result, it was difficult to perform leak diagnosis of the evaporated fuel sealing system with high accuracy.

  The present invention has been made to solve the above problems, and provides an evaporative fuel processing apparatus capable of performing leak diagnosis of an evaporative fuel sealing system with high accuracy even when applied to, for example, a hybrid vehicle. The purpose is to do.

  In order to achieve the above object, the invention according to (1) is provided in a fuel tank that is mounted on a vehicle equipped with an internal combustion engine and accommodates fuel, and a communication passage that connects between the fuel tank and the atmosphere. A canister for recovering the evaporated fuel discharged through the communication path, an open / close valve provided in a communication path connecting the canister and the atmosphere, and opening or closing the canister to the atmosphere, and a fuel tank A tank internal pressure detection unit that detects an internal pressure; a control unit that issues a command to open or close the on-off valve; and a diagnosis unit that performs a leak diagnosis of an evaporative fuel sealing system including the fuel tank.

  The diagnostic unit correlates with the twice differential value of the tank internal pressure by the tank internal pressure detection unit when the on-off valve is closed in accordance with the command of the control unit after the ignition switch of the vehicle is turned off. The evaporative fuel using the stagnation time method based on the relationship between the tank internal pressure detected by the tank internal pressure detection unit and the stagnation time of the tank internal pressure while performing a leak diagnosis of the evaporative fuel sealing system using a parameter-based two-derivative method The leak diagnosis of the closed system is performed, and the leak diagnosis result using the stagnation time method is preferentially used with respect to the leak diagnosis result using the twice differential method.

  In the invention according to (1), the leak diagnosis result using the stagnation time method having higher diagnostic accuracy than the two-time differential method is preferentially used for the leak diagnosis result using the two-time differential method. Specifically, for example, when the leak diagnosis result using the stagnation time method is normal with no leak, the diagnosis unit indicates that the leak diagnosis is normal regardless of whether the leak diagnosis result using the twice differential method is used. Make a diagnosis of

  According to the invention according to (1), the leak diagnosis result using the stagnation time method having higher diagnostic accuracy than the twice differential method is preferentially used for the leak diagnosis result using the double differential method. Therefore, for example, even when applied to a hybrid vehicle, leak diagnosis of the evaporated fuel sealing system can be performed with high accuracy.

  The invention according to (2) is the invention according to (1), and the diagnosis time for obtaining the leak diagnosis result using the stagnation time method is for obtaining the leak diagnosis result using the twice differential method. It is characterized in that the time length is set to be longer than the diagnosis time.

  According to the invention according to (2), the diagnosis time for obtaining the leak diagnosis result using the stagnation time method is longer than the diagnosis time for obtaining the leak diagnosis result using the twice differential method. Therefore, the leakage diagnosis of the evaporated fuel sealing system can be performed with higher accuracy.

The invention according to (3) is the invention according to (1) or (2), in which the diagnosis unit is configured to perform the opening / closing valve in accordance with the command from the control unit after the ignition switch of the vehicle is turned off. In the first diagnosis stage in which the tank is closed, the first leak diagnosis is performed based on the relationship between the tank internal pressure detected by the tank internal pressure detection unit and the first threshold value set in advance, and the first leak diagnosis is completed. Thereafter, in a second diagnosis stage in which the on-off valve is in a closed state according to the command of the control unit, a pressure fluctuation detection method based on a relationship between a tank internal pressure by a tank internal pressure detection unit and a predetermined second threshold value, A second leak diagnosis using the differential differentiation method and the stagnation time method is performed.
The on-off valve is opened once after the first leak diagnosis is completed according to the command of the control unit. If the result of the second leak diagnosis using the pressure fluctuation detection method is normal without a leak, the diagnosis unit determines whether the result of the second leak diagnosis using the second differential method or the stagnation time method is used. Regardless, it is characterized by making a diagnosis of normality without leaks.

  According to the invention according to (3), the diagnosis unit performs the second leak using the twice differential method or the stagnation time method when the result of the second leak diagnosis using the pressure fluctuation detection method is normal without leak. Regardless of the result of the diagnosis, since the diagnosis that the leak is normal is made, the leak diagnosis of the evaporated fuel sealing system can be performed in a short time.

  According to the evaporated fuel processing apparatus of the present invention, for example, even when applied to a hybrid vehicle, leak diagnosis of the evaporated fuel sealing system can be performed with high accuracy.

It is a whole block diagram showing the outline | summary of the evaporative fuel processing apparatus which concerns on embodiment of this invention. It is a flowchart figure showing the flow of the leak diagnosis process which the evaporative fuel processing apparatus which concerns on embodiment of this invention performs. It is a flowchart figure showing the flow of the integrated leak diagnostic process which the evaporative fuel processing apparatus which concerns on embodiment of this invention performs. It is a time chart figure used for description of operation | movement of the evaporative fuel processing apparatus (at the time of normal without a leak) which concerns on the comparative example after switching an ignition switch from ON to OFF. It is a time chart figure used for description of operation | movement of the evaporative fuel processing apparatus (at the time of abnormality with a leak) which concerns on the comparative example after switching an ignition switch from on to off. It is a time chart figure used for operation | movement description of the evaporative fuel processing apparatus (at the time of normal without a leak) which concerns on embodiment of this invention after switching an ignition switch from on to off. It is a time chart figure used for operation | movement description of the evaporative fuel processing apparatus (at the time of normal without a leak) which concerns on embodiment of this invention after switching an ignition switch from on to off. It is a time chart figure used for operation | movement description of the evaporative fuel processing apparatus (at the time of abnormality with a leak) which concerns on embodiment of this invention after the ignition switch is switched from on to off.

  Hereinafter, an evaporative fuel processing apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Outline of Evaporative Fuel Processing Device 11 According to Embodiment of the Present Invention]
First, the outline of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention will be described with reference to FIG. 1 by taking an example of application to a hybrid vehicle including an internal combustion engine 13 and an electric motor (not shown) as drive sources. To do. FIG. 1 is an overall configuration diagram showing an outline of an evaporative fuel processing apparatus 11 according to an embodiment of the present invention.
In addition, in drawing shown below, the same referential mark shall be attached | subjected between the same members or corresponding members. In addition, the size and shape of the member may be schematically represented by being modified or exaggerated for convenience of explanation.

  As shown in FIG. 1, the evaporative fuel processing device 11 that plays a role in processing evaporative fuel is mounted on a vehicle equipped with an internal combustion engine 13 and contains a fuel tank 15 that contains fuel such as gasoline, and a fuel tank 15. A canister 17 having a function of adsorbing evaporated fuel, an ECU (Electronic Control Unit) 19 that performs overall control of the evaporated fuel processing device 11, and the like are provided.

  A fuel inlet pipe 21 is provided in the fuel tank 15. A fuel inlet 21 a into which a nozzle (both not shown) of a fuel gun is inserted is provided on the fuel inlet pipe 21 on the opposite side of the fuel tank 15. A screw-type filler cap 23 is attached to the oil filler port 21a.

  The fuel tank 15 is provided with an evaporated fuel discharge passage 25 that connects the fuel tank 15 and the canister 17 in communication. The evaporated fuel discharge passage 25 has a function as a flow passage for the evaporated fuel. The canister 17 is provided with an atmospheric flow passage 26 that communicates and connects the canister 17 and the atmosphere. The large air flow passage 26 functions as an air flow passage. The evaporated fuel discharge passage 25 and the atmospheric flow passage 26 correspond to the “communication passage” of the present invention.

  A tank internal pressure sensor 27 is provided in the evaporated fuel discharge passage 25. The tank internal pressure sensor 27 corresponding to the “tank internal pressure detection unit” of the present invention detects a tank internal pressure Ptank, which is a pressure in the gas phase region in the fuel tank 15 (pressure in the “evaporated fuel sealing system” of the present invention). It has a function. However, a configuration in which the tank internal pressure sensor 27 is provided directly to the fuel tank 15 may be employed. As a pressure detection part of the tank internal pressure sensor 27, for example, a piezoelectric element can be used. Information relating to the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is sent to the ECU 19.

  When the canister 17 communicates with the atmosphere by opening the atmosphere opening / closing valve 29, the tank internal pressure sensor 27 can detect the atmospheric pressure. On the other hand, when the “evaporated fuel sealing system” is configured by closing the atmospheric on-off valve 29 and the purge control valve 35, the tank internal pressure sensor 27 can detect a change in the tank internal pressure Ptank related to the fuel tank 15.

  An atmospheric opening / closing valve 29 is provided in the large air flow passage 26. The atmospheric on / off valve 29 corresponding to the “open / close valve” of the present invention has a function of opening or closing the internal space of the canister 17 with respect to the atmosphere. Specifically, the atmospheric opening / closing valve 29 is a normally closed electromagnetic valve that operates according to a control signal sent from the ECU 19. The atmospheric opening / closing valve 29 operates so as to communicate between the canister 17 and the atmosphere by closing according to an opening control signal from the ECU 19 while closing between the canister 17 and the atmosphere by closing when not energized.

  The canister 17 incorporates an adsorbent (not shown) made of activated carbon for adsorbing the evaporated fuel. The adsorbent of the canister 17 adsorbs the evaporated fuel sent from the fuel tank 15 side via the evaporated fuel discharge passage 25. In addition to the atmospheric flow passage 26, the canister 17 is connected to a purge passage 31 used for performing a purge process. The canister 17 is connected to an intake pipe (intake manifold) 33 through a purge passage 31.

  In the purge process, the purge control valve 35 described below is opened so that the evaporated fuel adsorbed by the adsorbent of the canister 17 is taken in through the purge passage 31 together with the air taken in through the atmospheric flow passage 26. Sent to the tube 33.

  A purge control valve 35 is provided in the purge passage 31. The purge control valve 35 has a function of opening or closing a purge passage 31 that communicates between the canister 17 and the intake pipe 33. Specifically, the purge control valve 35 is a normally closed electromagnetic valve that operates according to a control signal sent from the ECU 19. The purge control valve 35 closes when not energized to shut off the canister 17 and the intake pipe 33, and opens according to an open control signal from the ECU 19 to operate the canister 17 and the intake pipe 33 to communicate with each other. .

  Here, the “evaporated fuel sealing system” of the present invention is defined by the fuel tank 15, the evaporated fuel discharge passage 25, the canister 17, the atmospheric flow passage 26 and the atmospheric opening / closing valve 29, and the purge passage 31 and the purge control valve 35. A closed space.

  The fuel tank 15 and the intake pipe 33 are connected to each other via a fuel supply passage 37. The fuel supply passage 37 is provided with a fuel pump module 39 that pumps up the fuel stored in the fuel tank 15 and sends it to the fuel injection valve 41. The fuel injected from the fuel injection valve 41 is supplied to the internal combustion engine 13 while being mixed with the air supplied from the intake pipe 33.

  As shown in FIG. 1, the tank internal pressure sensor 27, the ignition switch 43, the atmospheric pressure sensor 45, and the vehicle speed sensor 47 are connected to the ECU 19 as an input system. The vehicle speed sensor 47 has a function of detecting the speed of the host vehicle (not shown). Information relating to the speed of the host vehicle detected by the vehicle speed sensor 47 is sent to the ECU 19.

  As shown in FIG. 1, the ECU 19 is connected to the atmospheric on-off valve 29, the purge control valve 35, the fuel pump module 39, and the fuel injection valve 41 as output systems.

  As shown in FIG. 1, the ECU 19 includes a storage unit 51, a diagnosis unit 53, and a control unit 55. The ECU 19 is configured by a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The microcomputer reads and executes programs and data stored in the ROM, and operates to perform overall control of the leak diagnosis function of the ECU 19 and the entire evaporated fuel processing apparatus 11.

  The storage unit 51 stores the first threshold value P_th1, the second threshold value P_th2, the first diagnosis period dt1 related to the first diagnosis stage, the second diagnosis period dt2 related to the second leak diagnosis, and the atmosphere opening / closing valve 29. It has a function of storing the opening setting time ot and the like. The opening / closing time ot of the air opening / closing valve 29 may be set appropriately as long as the pressure of the evaporated fuel sealing system (tank pressure Ptank) is reset to the atmospheric pressure.

  The first and second threshold values P_th1 and P_th2, the first and second diagnostic periods dt1 and dt2, and the opening / closing set time ot of the atmospheric on-off valve 29 stored in the storage unit 51 are stored in the diagnosis unit 53 in the first to be described later. In addition, it is referred to as appropriate when performing a leak diagnosis in the second diagnosis stage.

  The diagnosis unit 53 has a function of performing leak diagnosis of the evaporated fuel sealing system. More specifically, the diagnosis unit 53 performs the tank operation by the tank internal pressure sensor 27 in the first diagnosis stage in which the atmospheric on-off valve 29 is closed in accordance with the close command of the control unit 55 after the ignition switch 43 of the host vehicle is turned off. The first leak diagnosis is performed based on the relationship between the internal pressure Ptank and the first threshold value P_th1, and after the first leak diagnosis is performed, the atmospheric on-off valve 29 is closed according to the closing command of the control unit 55. In the diagnosis stage, the second leak diagnosis is performed based on the relationship between the tank internal pressure Ptank and the second threshold value P_th2 by the tank internal pressure sensor 27.

  Here, in the embodiment according to the present invention, a pressure fluctuation detection method (hereinafter referred to as “PFD method”), a two-time differential method (hereinafter referred to as “DDP method”), as a leakage diagnosis method for a fuel vapor sealing system. And a stagnation time method (hereinafter referred to as “DTM method”). When performing leak diagnosis using the PFD method, the DDP method, and the DTM method, it is assumed that an evaporative fuel sealing system is configured (the atmospheric on-off valve 29 and the purge control valve 35 are in a closed state).

  The leak diagnosis method using the DDP method and the DTM method is described in detail in, for example, Japanese Patent Application Laid-Open No. 2006-77595. This publication is incorporated herein by reference. Therefore, the description of the leak diagnosis method using the DDP method and the DTM method is briefly described.

  First, the principle common to the leak diagnosis methods related to the PFD method, the DDP method, and the DTM method will be described. In general, on the assumption that the evaporative fuel sealing system is configured normally (no leakage), if the time from when the internal combustion engine 13 is stopped (ignition switch 43 is turned off) elapses, the tank internal pressure Ptank is near atmospheric pressure. Often deviates from (predetermined allowable range including atmospheric pressure, the same applies hereinafter). This is because evaporative fuel is generally generated inside the fuel tank 15 of the parked vehicle under the influence of the residual heat of the internal combustion engine 13 and the environmental temperature.

  However, if a leak occurs in the evaporative fuel sealing system including the fuel tank 15, the time-dependent characteristic of the tank internal pressure Ptank shows a unique tendency, for example, converges to the vicinity of the atmospheric pressure. Therefore, it is possible to diagnose whether or not there is a leak in the fuel vapor sealing system based on whether or not the time-dependent characteristics of the tank internal pressure Ptank show the above-mentioned tendency.

  Next, an outline of the PFD method will be described. When the evaporative fuel sealing system is normal (no leak), the time-dependent characteristic related to the tank internal pressure Ptank detected by the tank internal pressure sensor 27 tends to increase almost linearly with a relatively large slope, In the case of abnormality (there is a leak), the time-dependent characteristic related to the tank internal pressure Ptank initially increases at a relatively large rate of change (the slope of the time-dependent characteristic diagram related to the tank internal pressure Ptank), but a certain pressure level corresponding to the hole diameter In many cases, the rate of change (the slope of the time-dependent characteristic diagram) gradually decreases thereafter.

Therefore, by evaluating the tendency of the time-dependent characteristics related to the tank internal pressure Ptank, it is possible to diagnose whether or not there is a leak in the evaporated fuel sealing system. Specifically, the leak diagnosis is performed based on the relationship between the tank internal pressure Ptank by the tank internal pressure sensor 27 and a predetermined threshold (for example, the first threshold P_th1 and the second threshold P_th2). When the tank internal pressure Ptank by the tank internal pressure sensor 27 exceeds a threshold value (for example, the first threshold value P_th1 and the second threshold value P_th2), a diagnosis is made that the fuel vapor sealing system is normal (no leak).
Therefore, according to the PFD method, it is determined whether the tank internal pressure Ptank after the internal combustion engine 13 is stopped (ignition switch 43 is turned off) exceeds a threshold (for example, the first threshold P_th1 and the second threshold P_th2). Through the determination, the leak diagnosis of the evaporated fuel sealing system can be performed.

  Next, an outline of the DDP method will be described. When the evaporative fuel sealing system is normal (no leakage), the time-dependent characteristics related to the tank internal pressure Ptank detected by the tank internal pressure sensor 27 tend to increase almost linearly, while the evaporative fuel sealing system is abnormal (leakage). In this case, the time-dependent characteristic related to the tank internal pressure Ptank initially increases at a relatively large change rate (the slope of the time-dependent characteristic diagram related to the tank internal pressure Ptank), but the rate of change (the slope of the time-dependent characteristic diagram) gradually increases. It shows a decreasing trend.

Therefore, by evaluating the tendency of the time-dependent characteristics related to the tank internal pressure Ptank, it is possible to diagnose whether or not there is a leak in the evaporated fuel sealing system. Specifically, in order to perform a highly accurate leak diagnosis even if the amount of evaporated fuel generated varies, a twice differential value (including a correlation value of the twice differential value) obtained by differentiating the tank internal pressure Ptank is determined. Used as a parameter. Then, the determination parameter is substantially “0” at the normal time, whereas the determination parameter has a negative value at the abnormal time.
Therefore, according to the DDP method, the leakage diagnosis of the evaporated fuel sealing system can be performed by evaluating the value taken by the determination parameter.

  By the way, in the DDP method described above, it is difficult to detect a leak abnormality when a relatively small hole is formed in the evaporative fuel sealing system and the gradient of the time characteristic diagram related to the tank internal pressure Ptank is gentle. In this way, in the case where a leak due to a small hole (hereinafter referred to as “small hole leak”) occurs, the DTM method described below is effective.

  First, a time during which the tank internal pressure Ptank detected by the tank internal pressure sensor 27 converges (continuously) within a predetermined pressure range is defined as a stagnation time TSTY. Then, taking the tank internal pressure Ptank as the x-axis and the stagnation time TSTY as the y-axis, a correlation characteristic diagram showing the transition of the stagnation time TSTY accompanying the change in the tank internal pressure Ptank is created, and the regression line related to the correlation characteristic diagram Draw a diagram. Focusing on the slope of the regression line relating to the correlation characteristic diagram representing the transition of the stagnation time TSTY accompanying the change of the tank internal pressure Ptank, when the evaporated fuel sealing system is normal (no leak), the slope of the regression line is While taking a relatively small positive value, when the fuel vapor seal system is abnormal (leak), the slope of the regression line takes a negative value with a large absolute value.

  Therefore, according to the DTM method, the presence or absence of a leak including a small hole leak is diagnosed through evaluation of whether the slope of the regression line relating to the correlation characteristic diagram is positive or negative and its magnitude relationship. can do.

  The control unit 55 has a function of performing overall control of the entire evaporated fuel processing apparatus 11. Further, the control unit 55 has a function of giving a command to close the atmospheric on-off valve 29 and the purge control valve 35 after the ignition switch 43 of the vehicle is turned off (stop of the internal combustion engine 13), for example. However, when adopting a configuration in which the power supply to the purge control valve 35 is stopped when the ignition switch 43 is turned off, the control unit 55 can omit the function of instructing the purge control valve 35 to close. .

[Operation of Evaporative Fuel Processing Device 11 According to Embodiment of the Present Invention]
Next, the operation of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention will be described with reference to FIG. 2A.
FIG. 2A is a flowchart showing the flow of a leak diagnosis process executed by the evaporated fuel processing apparatus 11 according to the embodiment of the present invention.

  In step S11 shown in FIG. 2A, the ECU 19 checks whether or not the ignition switch 43 is turned off. The ECU 19 repeats the determination process of step S11 until it is determined that the ignition switch 43 has been turned off.

  As a result of the determination in step S11, if it is determined that the ignition switch 43 has been turned off ("Yes" in step S11), the ECU 19 advances the process flow to the next step S12.

  In step S <b> 12, the control unit 55 of the ECU 19 performs control for closing the atmospheric opening / closing valve 29. As a result, when the atmospheric on-off valve 29 is closed and the purge control valve 35 is closed (by power supply stop), an evaporative fuel sealing system is configured, and the leak diagnosis is ready.

  In step S13, the diagnosis unit 53 executes the first leak diagnosis. The first leak diagnosis is a leak diagnosis procedure for the fuel vapor sealing system using the PFD method (pressure fluctuation detection method) performed by the diagnosis unit 53 in the first diagnosis stage that starts immediately after the ignition switch 43 is turned off. . The first diagnosis period dt1 related to the first diagnosis stage is necessary for the tank internal pressure Ptank detected by the tank internal pressure sensor 27 to be stable from the time when the ignition switch 43 is turned off as compared to immediately after the ignition switch 43 is turned off. Then, it is assumed to be a stable time, and is set to a shorter time length than a second diagnosis period dt2 related to a second diagnosis stage described later. Details of the first leak diagnosis will be described later.

  In step S14, the ECU 19 refers to the first diagnosis period dt1 stored in the storage unit 51, and determines whether or not the elapsed time from the time when the ignition switch 43 is turned off has reached the first diagnosis period dt1 ( It is checked whether or not the first leak diagnosis is completed. The ECU 19 repeats the determination process in step S14 until it is determined that the elapsed time from the time when the ignition switch 43 is turned off has reached the first diagnosis period dt1 (the first leak diagnosis has been completed). .

  As a result of the determination in step S14, if it is determined that the elapsed time from the time when the ignition switch 43 is turned off has reached the first diagnosis period dt1 (the first leak diagnosis has ended) (in step S14) "Yes"), the ECU 19 advances the flow of processing to the next step S15.

  In step S <b> 15, the control unit 55 of the ECU 19 performs control to open the atmospheric opening / closing valve 29. Thereby, when the atmospheric on-off valve 29 is opened, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 converges to atmospheric pressure.

  In step S <b> 16, the ECU 19 refers to the opening / closing time ot of the atmospheric opening / closing valve 29 stored in the storage unit 51, and has the opening time of the atmospheric opening / closing valve 29 reached the opening setting time ot of the atmospheric opening / closing valve 29? Check for no. The ECU 19 repeats the determination process in step S16 until it is determined that the opening time of the atmospheric opening / closing valve 29 has reached the opening setting time ot of the atmospheric opening / closing valve 29.

  As a result of the determination in step S16, when it is determined that the open time of the atmospheric on / off valve 29 has reached the open set time ot of the atmospheric on / off valve 29 ("Yes" in step S16), the ECU 19 The flow is advanced to the next step S17.

  In step S <b> 17, the control unit 55 of the ECU 19 performs control to switch the atmospheric opening / closing valve 29 from the open state to the closed state. As a result, when the atmospheric on-off valve 29 is closed (the purge control valve 35 is kept closed by stopping the power supply), the fuel vapor sealing system is configured and the leak diagnosis is ready.

  In step S18, the diagnosis unit 53 performs a second leak diagnosis. The second leak diagnosis means that after the first leak diagnosis is finished, the air opening / closing valve 29 is once opened in accordance with the closing instruction of the control unit 55, and then, in the second diagnosis stage in the closed state, the diagnosis unit 53 This is a leak diagnosis procedure for an evaporative fuel sealing system using a combination of a PFD method (pressure fluctuation detection method), a DDP method (double differential method), and a DTM method (stagnation time method). The second diagnosis period dt2 related to the second diagnosis stage is set to a sufficiently long time length compared to the first diagnosis period dt1 related to the first diagnosis stage. Details of the second leak diagnosis will be described later.

  In step S19, the ECU 19 refers to the second diagnosis period dt2 stored in the storage unit 51, and the elapsed time from the time when the atmospheric on-off valve 29 is switched from the open state to the closed state is the second diagnosis period. It is checked whether or not the period dt2 has been reached (whether or not the second leak diagnosis has ended). The ECU 19 determines that the elapsed time from when the atmospheric on-off valve 29 is switched from the open state to the closed state has reached the second diagnosis period dt2 (the second leak diagnosis has been completed). Until this, the determination process in step S19 is repeated.

  As a result of the determination in step S19, it is determined that the elapsed time from the time when the atmospheric on-off valve 29 is switched from the open state to the closed state has reached the second diagnosis period dt2 (the second leak diagnosis has been completed). When (Yes in step S19) is established, the ECU 19 advances the process flow to the next step S20.

  In step S20, the diagnosis unit 53 of the ECU 19 executes integrated leak diagnosis. The integrated leak diagnosis is an evaporative fuel sealing system for obtaining an integrated leak diagnosis result obtained by integrating the first and second leak diagnosis results, which is performed by the diagnosis unit 53 after completion of the first and second leak diagnosis. This is a leak diagnosis procedure. Details of the integrated leak diagnosis will be described below.

[Integrated Leak Diagnosis Performed by Evaporative Fuel Processing Apparatus 11 According to Embodiment of Present Invention]
Next, the integrated leak diagnosis executed by the evaporated fuel processing apparatus 11 according to the embodiment of the present invention will be described with reference to FIG. 2B.
FIG. 2B is a flowchart showing the flow of the integrated leak diagnosis process executed by the evaporated fuel processing apparatus 11 according to the embodiment of the present invention.

The integrated leak diagnosis shown in FIG. 2B is performed after the first and second leak diagnosis results are obtained in the diagnosis unit 53.
Note that, as described above, in the first leak diagnosis, the leak diagnosis of the evaporated fuel sealing system using the PFD method (pressure fluctuation detection method) is performed, while in the second leak diagnosis, the PFD method (pressure fluctuation detection method). ), The DDP method (double differential method), and the DTM method (stagnation time method) are used for leak diagnosis of the evaporative fuel sealing system.

  In step S31 shown in FIG. 2B, the diagnosis unit 53 determines that the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is near atmospheric pressure based on the second leak diagnosis result using the PFD method (pressure fluctuation detection method). Check to see if you are stuck. Specifically, the diagnosis unit 53 determines that the tank internal pressure Ptank detected by the tank internal pressure sensor 27 in the second diagnosis period dt2 related to the second diagnosis stage is near atmospheric pressure (a predetermined pressure including atmospheric pressure). When the pressure is converged to the permissible range, a diagnosis is made that the tank internal pressure Ptank is stagnating near atmospheric pressure.

  As a result of the determination in step S31, when it is determined that the tank internal pressure Ptank is not stagnating in the vicinity of the atmospheric pressure (“No” in step S31), the diagnosis unit 53 moves the process flow to the next step S32. Go ahead.

On the other hand, if it is determined in step S31 that the tank internal pressure Ptank is stagnating near atmospheric pressure (“Yes” in step S31), the diagnosis unit 53 moves the process flow to step S35. Jump to “Integrated NG”.
“Integrated NG” means that the integrated leak diagnosis result obtained by integrating the first and second leak diagnosis results is “NG (abnormality with leak)”.

  In step S32, the diagnosis unit 53 determines whether the second leak diagnosis result using the DTM method (stagnation time method) is an abnormality with a leak, normal with no leak, or normal with no diagnosis, and is suspended. .

  As a result of the determination in step S32, when it is determined that the second leak diagnosis result using the DTM method cannot be diagnosed and is suspended (“pending” in step S32), the diagnosis unit 53 performs processing. The flow is advanced to the next step S33.

  As a result of the determination in step S32, when it is determined that the second leak diagnosis result using the DTM method is abnormal with a leak (“Yes” in step S32), the diagnosis unit 53 performs processing. Is jumped to “integrated NG” in step S35.

Furthermore, when it is determined that the second leak diagnosis result using the DTM method is normal with no leak as a result of the determination in step S32 (“No” in step S32), the diagnosis unit 53 performs processing. Is jumped to “integrated OK” in step S37.
“Integrated OK” means that the integrated leak diagnosis result is “OK (no leak normal)”.

  In short, in the second leak diagnosis result determination using the DTM method in step S32, if it is determined that there is an abnormality with leak or normal without leak, the second leak diagnosis using the DDP method (double differential method) in step S34 is performed. Regardless of the leak diagnosis result, the second leak diagnosis result using the DTM method is preferentially used to give the integrated leak diagnosis result. This is because the DTM method generally provides a more accurate leak diagnosis result than the DDP method.

In step S33, in the second diagnosis stage, the diagnosis unit 53 determines that the maximum value Pmax of the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is the minimum value DDPmin of the tank internal pressure Ptank that allows leak diagnosis using the DDP method. It is determined whether or not it exceeds.
In the DDP method, in the case where the maximum value Pmax of the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is lower than the minimum value DDPmin of the tank internal pressure Ptank, which is the lower limit of application of the DDP method, the leak diagnosis of the evaporated fuel sealing system is appropriately performed. It becomes difficult to do.
According to step S33, it is possible to easily and quickly determine whether or not the leak diagnosis using the DDP method in the second diagnosis stage is effective.

  However, the minimum value DDPmin of the tank internal pressure Ptank capable of leak diagnosis using the DDP method may be a fixed value determined in advance or a variable value according to a parameter related to the DDP method.

  As a result of the determination in step S33, when it is determined that the maximum value Pmax of the tank internal pressure Ptank exceeds the minimum value DDPmin of the tank internal pressure Ptank that allows leak diagnosis using the DDP method (" Yes "), the diagnosis unit 53 advances the process flow to the next step S34.

On the other hand, as a result of the determination in step S33, it is determined that the maximum value Pmax of the tank internal pressure Ptank does not exceed the minimum value DDPmin of the tank internal pressure Ptank that allows leak diagnosis using the DDP method (step S33). No)), the diagnosis unit 53 causes the process flow to jump to “integration hold” in step S36.
Note that “integrated hold” means that the integrated leak diagnosis result is “hold (including undiagnosable)”.

  In step S <b> 34, the diagnosis unit 53 determines whether the second leak diagnosis result using the DDP method is an abnormality with a leak, a normal with no leak, or a diagnosis with no suspension.

  As a result of the determination in step S34, when it is determined that the second leak diagnosis result using the DDP method is on hold (“hold” in step S32), the diagnosis unit 53 steps the process flow. Proceed to “integration hold determination” in S36.

  As a result of the determination in step S34, when it is determined that the second leak diagnosis result using the DDP method is abnormal with a leak (“Yes” in step S34), the diagnosis unit 53 performs processing. Is jumped to “integrated NG” in step S35.

  Furthermore, when it is determined that the second leak diagnosis result using the DDP method is normal with no leak as a result of the determination in step S34 (“No” in step S34), the diagnosis unit 53 performs processing. Is jumped to “integrated OK” in step S37.

  In short, in the second leak diagnosis result determination using the DDP method in step S34, as the second leak diagnosis result using the PFD method in step S31, it is determined that the tank internal pressure Ptank is not stagnating near the atmospheric pressure. When the second leak diagnosis result using the DTM method in step S32 is pending, the second leak diagnosis result using the DDP method, which is inferior to the DTM method, is used as it is. Using the integrated leak diagnosis result.

[Time Series Operation of Evaporative Fuel Processing Apparatus According to Comparative Example]
Next, the time-series operation of the evaporated fuel processing apparatus according to the comparative example will be described with reference to FIGS. 3A and 3B.
FIG. 3A is a time chart for explaining the operation of the fuel vapor processing apparatus according to the comparative example (when there is no leak) after the ignition switch 43 is switched from on to off. FIG. 3B is a time chart for explaining the operation of the fuel vapor processing apparatus according to the comparative example (when there is an abnormality with a leak) after the ignition switch 43 is switched from on to off.

  The evaporated fuel processing apparatus 11 according to the embodiment of the present invention and the evaporated fuel processing apparatus according to the comparative example are mainly different in the following two points.

  The first difference is that, in the fuel vapor processing apparatus 11 according to the embodiment of the present invention, at the first diagnosis stage (within a stable time assumed to be required for stabilization compared to immediately after the ignition switch 43 is turned off). While the leak diagnosis is performed (atmospheric open / close valve 29 is closed), the fuel vapor processing apparatus according to the comparative example does not perform the leak diagnosis within the time corresponding to the first diagnosis stage (atmospheric open / close valve 29 is opened). Maintain state).

  The second difference is that, in the fuel vapor processing apparatus 11 according to the embodiment of the present invention, the second diagnosis stage (after the elapse of the stable time assumed to be required for stabilization compared to immediately after the ignition switch 43 is turned off). ), The leak diagnosis result by the DTM method is preferentially adopted as the integrated leak diagnosis result, and the leak diagnosis result by the DDP method is used as the integrated leak diagnosis result when the leak diagnosis result by the DTM method is pending (including undiagnosable) As a result, the fuel vapor treatment apparatus according to the comparative example adopts the leak diagnosis result by the DDP method preferentially as the integrated leak diagnosis result, and preliminarily uses the leak diagnosis result by the DTM method. It is a point to adopt.

First, the operation of the evaporated fuel processing apparatus according to the comparative example when there is no leak will be described. As a premise, it is assumed that the season is spring and the environmental temperature is, for example, about 20 degrees Celsius.
When the ignition switch 43 is switched from on to off at time t1 shown in FIG. 3A (see FIG. 3A), a leak diagnosis timer (not shown) starts counting.

  At time t1 shown in FIG. 3A, the operation of each part other than the ignition switch 43 belonging to the evaporated fuel processing apparatus according to the comparative example is as follows. That is, the air opening / closing valve 29 is maintained in an open state (see FIG. 3A (b)). The tank internal pressure Ptank detected by the tank internal pressure sensor 27 indicates the atmospheric pressure (see FIG. 3A (c)). The leak diagnosis flag indicating the leak diagnosis result is in a pending state before the leak diagnosis (see FIG. 3A (d)).

At time t1-t2 shown in FIG. 3A, the ignition switch 43 continues to be in the off state.
At the same time t1-t2 shown in FIG. 3A, the operation of each part other than the ignition switch 43 belonging to the evaporated fuel processing apparatus according to the comparative example is the same as that at time t1. That is, the air opening / closing valve 29 is maintained in an open state (see FIG. 3A (b)). The tank internal pressure Ptank detected by the tank internal pressure sensor 27 indicates the atmospheric pressure (see FIG. 3A (c)). The leak diagnosis flag is in a pending state before the leak diagnosis (see FIG. 3A (d)).

At time t2 shown in FIG. 3A, the atmospheric on-off valve 29 is switched from the open state to the closed state (see FIG. 3A (b)).
The time t2 is a timing at which the count value of the leak diagnosis timer reaches a value corresponding to a stable time that is assumed to be required for stabilization compared to immediately after the ignition switch 43 is turned off. That is, the period related to the time t1-t2 shown in FIG. 3A corresponds to the first diagnosis period dt1 related to the first diagnosis stage according to the embodiment of the present invention. In the fuel vapor processing apparatus according to the comparative example, as described above, the leak diagnosis is not performed in the period related to the time t1-t2.

  The tank internal pressure Ptank detected by the tank internal pressure sensor 27 at the time t2-t4 shown in FIG. 3A is equal to the atmospheric pressure stagnation region (at the positive pressure side and the negative pressure side with respect to the atmospheric pressure) at the time t3 shown in FIG. 3A. It shows a tendency to converge in the atmospheric pressure stagnation region again after deviating from the pressure region having a margin that can be regarded as the vicinity of the atmospheric pressure; see FIG. 3A (c)) to the positive pressure side (see FIG. 3A (c)).

  Here, the evaporative fuel sealing system is configured so that the tank internal pressure Ptank detected by the tank internal pressure sensor 27 deviates from the atmospheric pressure stagnation region (see time t3 shown in FIG. 3A). This is a phenomenon that occurs in the normal case without leaks. Thereby, the evaporative fuel processing apparatus according to the comparative example integrates the leak diagnosis result by the DDP method based on the leak diagnosis result using the PFD method and the leak diagnosis result using the DDP method and the DTM method. From the viewpoint of preliminarily adopting as a result and preliminarily adopting the leak diagnosis result by the DTM method, a diagnosis is made that the evaporative fuel sealing system is normal without leak (OK state).

  The leak diagnosis period related to time t2-t4 shown in FIG. 3A corresponds to the second diagnosis period dt2 related to the second diagnosis stage related to the embodiment of the present invention. In the comparative example, as in the embodiment of the present invention, in addition to the leak diagnosis using the PFD method (see the time-dependent characteristic diagram relating to the tank internal pressure Ptank in FIG. 3A (c)) in the period relating to the time t2-t4. In addition, leak diagnosis (not shown) using the DDP method and the DTM method is performed. However, in the comparative example, as described above as the second difference, the leak diagnosis result by the DDP method is preferentially adopted as the integrated leak diagnosis result, and the leak diagnosis result by the DTM method is preliminarily adopted. Yes.

  At time t2-t4 shown in FIG. 3A, the ignition switch 43 is kept off. The atmospheric opening / closing valve 29 maintains a closed state (see FIG. 3A (b)). The leak diagnosis flag shifts from the hold state to the OK state at time t3 shown in FIG. 3A, and then maintains the OK state until time t4 and thereafter (see FIG. 3A (d)).

  Next, the operation of the evaporated fuel processing apparatus according to the comparative example when there is a leak abnormality will be described. However, since the operation at time t1-t2 shown in FIG. 3B is the same as that at normal time without leakage, redundant description will be omitted, and operation after time t2 will be described.

  In the leak diagnosis period related to time t2-t4 shown in FIG. 3B, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is maintained in a state of being converged in the atmospheric pressure stagnation region (see FIG. 3B (c)). .

  Here, while the evaporated fuel sealing system is configured, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is maintained in a state where it converges in the atmospheric pressure stagnation region. It is a phenomenon that occurs in a case. As a result, the evaporative fuel processing apparatus according to the comparative example, at time t4 when the leak diagnosis period ends, based on the leak diagnosis result using the PFD method and the leak diagnosis result using the DDP method and the DTM method, From the viewpoint of preferentially adopting the leak diagnosis result by the method as the integrated leak diagnosis result and preliminarily adopting the leak diagnosis result by the DTM method, the diagnosis that the evaporative fuel sealing system is abnormal with leak (NG state) I will give you.

  At time t2 to t4 shown in FIG. 3B, the ignition switch 43 is maintained in the off state. The atmospheric opening / closing valve 29 maintains a closed state (see FIG. 3B (b)). The leak diagnosis flag shifts from the hold state to the NG state at time t4 shown in FIG. 3B (see FIG. 3B (d)).

[Time Series Operation of Evaporative Fuel Processing Apparatus 11 According to Embodiment of the Present Invention]
Next, the time series operation of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention will be described with reference to FIGS. 4A to 4C.
FIGS. 4A and 4B are time charts for explaining the operation of the evaporated fuel processing apparatus (when there is no leak) 11 according to the embodiment of the present invention after the ignition switch is switched from on to off. FIG. 4C is a time chart for explaining the operation of the fuel vapor processing apparatus 11 (at the time of abnormality with a leak) 11 according to the embodiment of the present invention after the ignition switch is switched from on to off.

First, the operation of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention when there is no leak will be described with reference to FIG. 4A. As a premise, it is assumed that the season is spring and the environmental temperature is, for example, about 20 degrees Celsius.
At time t11 shown in FIG. 4A, when the ignition switch 43 is switched from on to off (see FIG. 4A (a)), the leak diagnosis timer starts counting.

  At time t11 shown in FIG. 4A, the operation of each part other than the ignition switch 43 belonging to the evaporated fuel processing apparatus 11 according to the embodiment of the present invention is as follows. That is, the atmospheric on-off valve 29 is switched from the open state to the closed state (see FIG. 4A (b)). The tank internal pressure Ptank detected by the tank internal pressure sensor 27 indicates the atmospheric pressure (see FIG. 4A (c)). The leak diagnosis flag representing the leak diagnosis result is in a pending state before the leak diagnosis (see FIG. 4A (d)).

  Note that although the atmospheric on-off valve 29 has been described as being switched from the open state to the closed state in synchronization with the timing of the time t11 when the ignition switch 43 is switched from on to off, the present invention is limited to this example. Not. A configuration may be employed in which the atmospheric on-off valve 29 is switched from the open state to the closed state after a predetermined delay time (a time shorter than the time t12) from the time t11.

With this configuration, after the ignition switch 43 is switched from on to off at time t11, the first diagnosis period dt1 related to the first diagnosis stage is started (in this example, the first diagnosis is performed). The tank internal pressure Ptank can be stabilized before the period dt1 starts when a predetermined delay time elapses from the time t11.

  At time t11-t13 shown in FIG. 4A, the ignition switch 43 continues to be kept off. The atmospheric opening / closing valve 29 maintains a closed state (see FIG. 4A (b)). The tank internal pressure Ptank detected by the tank internal pressure sensor 27 continues from the positive pressure side after it has deviated from the atmospheric pressure stagnation region (described later; see FIG. 4A (c)) expanded at the time t12 shown in FIG. 4A. It shows a tendency to rise gently (see FIG. 4A (c)).

  Here, the expanded atmospheric pressure stagnation region is a first diagnostic stage used to determine whether or not the tank internal pressure Ptank detected by the tank internal pressure sensor 27 is stagnating in the vicinity of the atmospheric pressure. This is an area defined by a threshold value P_th1 of 1 (see FIG. 4A (c)).

  In the extended atmospheric pressure stagnation region, as described above, the first diagnosis period dt1 related to the first diagnosis stage is shorter than the second diagnosis period dt2 related to the second diagnosis stage described later. Therefore, the pressure range is (P_th1) as compared to the reference atmospheric pressure stagnation region (see FIG. 4A (c)) defined by the second threshold P_th2 used in the second diagnosis stage. -P_th2) is extended. This is based on performing a highly accurate leak diagnosis in a short time length.

A period related to time t11-t13 shown in FIG. 4A (a period within a stable time that is assumed to be required for the count value of the leak diagnostic timer to be stable compared to immediately after the ignition switch 43 is turned off (time t11)). This corresponds to the first diagnosis period dt1 according to the first diagnosis stage.
In the evaporated fuel processing apparatus 11 according to the embodiment of the present invention, the first leak diagnosis using the PFD method (pressure fluctuation detection method) is performed in the first diagnosis period dt1 corresponding to the time t11-t13. This is because immediately after the ignition switch 43 is turned off, the residual heat generated in the internal combustion engine 13 itself and the exhaust system of the internal combustion engine 13 is large, which is suitable for performing a leak diagnosis of the evaporated fuel sealing system.
The time t14 is a timing at which the count value of the leak diagnosis timer reaches a value corresponding to a stabilization time that is assumed to be required for stabilization compared to immediately after the ignition switch 43 is turned off (time t11). .

  Incidentally, in the fuel vapor processing apparatus according to the comparative example, the leak diagnosis is not performed in the period (period corresponding to the stabilization time) related to the time t1-t2 shown in FIG. 3A.

  By the way, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 deviates from the expanded atmospheric pressure stagnation region (see time t12 shown in FIG. 4A) in the first embodiment. This is a phenomenon that occurs in the case where the evaporative fuel sealing system is normal without leakage at the diagnosis stage. Thereby, the evaporative fuel processing apparatus 11 according to the embodiment of the present invention makes a diagnosis that the evaporative fuel sealing system is normal without leak (OK state) by the leak diagnosis using the PFD method at time t12. Therefore, the leak diagnosis flag indicating the leak diagnosis result shifts from the hold state to the OK state, and then maintains the OK state until time t16 and thereafter (see FIG. 4A (d)).

  At time t13 shown in FIG. 4A, the atmospheric on-off valve 29 is switched from the closed state to the open state in order to reset the history of the tank internal pressure Ptank related to the first leak diagnosis, and then opened until time t14. The state is maintained (see FIG. 4A (b)). At the same time t13 to t14, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 indicates the atmospheric pressure (see FIG. 4A (c)). The leak diagnosis flag representing the leak diagnosis result maintains the OK state (see FIG. 4A (d)).

When the atmospheric on-off valve 29 is switched from the open state to the closed state at time t14 shown in FIG. 4A, in the second diagnosis period dt2 (see times t14 to t16 shown in FIG. 4A) in the second diagnosis stage, In addition to the leak diagnosis using the PFD method (see the time characteristic diagram relating to the tank internal pressure Ptank in FIG. 4A (c)), the second leak diagnosis (not shown) using the DTM method and the DDP method is started. The
Incidentally, the second leak diagnosis performed at the times t14 to t16 of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention corresponds to the leak diagnosis performed at the times t2 to t4 of the evaporated fuel processing apparatus according to the comparative example. .

  At times t14 to t16 shown in FIG. 4A, the ignition switch 43 continues to be kept off. The atmospheric opening / closing valve 29 maintains a closed state (see FIG. 4A (b)). The tank internal pressure Ptank detected by the tank internal pressure sensor 27 is shifted from the reference atmospheric pressure stagnation region defined by the second threshold P_th2 used in the second diagnosis stage to the positive pressure side at time t15 shown in FIG. 4A. After deviating, it tends to converge again within the reference atmospheric pressure stagnation region (see FIG. 4A (c)).

  Here, when the fuel vapor sealing system is configured, the tank internal pressure Ptank detected by the tank internal pressure sensor 27 deviates from the reference atmospheric pressure stagnation region (see time t15 shown in FIG. 4A). This is a phenomenon that occurs in the case where the evaporative fuel sealing system is normal without leakage at the diagnosis stage. Therefore, the evaporative fuel processing apparatus 11 according to the embodiment of the present invention makes a diagnosis that the evaporative fuel sealing system is normal without leak (OK state) by the leak diagnosis using the PFD method at time t15. However, in the case shown in FIG. 4A, the leak diagnosis flag has already shifted from the hold state to the OK state at time t12. In this case, the fuel vapor processing apparatus 11 according to the embodiment of the present invention maintains the leak diagnosis flag as it is (see FIG. 4A (d)).

In the evaporated fuel processing apparatus 11 according to the embodiment of the present invention, the integrated leak diagnosis is performed according to the procedure based on FIG. 2B. Specifically, in this integrated leak diagnosis, in the second diagnosis stage, leak diagnosis using the DTM method and the DDP method is performed in addition to the leak diagnosis using the PFD method, starting at time t14. When leak diagnosis results by the PFD method, DTM method, and DDP method are obtained, in principle, the leak diagnosis result by the DTM method is preferentially adopted as the integrated leak diagnosis result, while the leak diagnosis result by the DDP method is used as the DTM method. This is secondarily adopted as the integrated leak diagnosis result when the leak diagnosis result is pending (including inability to diagnose).
However, if the leak diagnosis result using the PFD method is normal without leak (OK state), the leak diagnosis result according to the PFD method may be used preferentially with respect to the leak diagnosis result according to the DTM method and the DDP method. Good.

  Next, the operation of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention when there is no leak will be described with reference to FIG. 4B. 4A and the normal case shown in FIG. 4B have a common operation part. Therefore, in the case according to FIG. 4B, the duplicate description for the case according to FIG. 4A is omitted, and the description will be focused on the difference between the two.

  The difference between the two is that in the case according to FIG. 4A, a diagnosis without leak is made in both the first diagnosis stage and the second diagnosis stage, whereas in the case according to FIG. This is a point that a diagnosis without leak is made only in the diagnosis stage (no diagnosis without leak is made in the first diagnosis stage).

  Specifically, in the case according to FIG. 4B, the evaporated fuel processing apparatus 11 according to the embodiment of the present invention is normal in that the evaporated fuel sealing system has no leak by the leak diagnosis using the PFD method at time t <b> 15 illustrated in FIG. 4B. Make a diagnosis of (OK state). Then, at the same time t15, the leak diagnosis flag indicating the leak diagnosis result shifts from the hold state to the OK state, and then maintains the OK state until time t16 and thereafter (see FIG. 4B (d)).

In the evaporated fuel processing apparatus 11 according to the embodiment of the present invention, the integrated leak diagnosis is performed according to the procedure based on FIG. 2B, as in the case according to FIG. 4A. Specifically, in this integrated leak diagnosis, in the second diagnosis stage, leak diagnosis using the DTM method and the DDP method is performed in addition to the leak diagnosis using the PFD method, starting at time t14. When leak diagnosis results by the PFD method, DTM method, and DDP method are obtained, in principle, the leak diagnosis result by the DTM method is preferentially adopted as the integrated leak diagnosis result, while the leak diagnosis result by the DDP method is used as the DTM method. This is secondarily adopted as the integrated leak diagnosis result when the leak diagnosis result is pending (including inability to diagnose).
However, when the leak diagnosis result using the PFD method is normal without leak (OK state), the leak diagnosis result according to the PFD method is compared with the leak diagnosis result according to the DTM method and the DDP method as shown in FIG. 4B. May be used preferentially.

  Next, the operation of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention when there is a leak abnormality will be described with reference to FIG. 4C. A common operation part exists in the case of normal operation without leak shown in FIG. 4A and the case of abnormal operation with leak shown in FIG. 4C. Therefore, in the case according to FIG. 4C, the duplicate description for the case according to FIG. 4A will be omitted, and the description will be focused on the difference between them.

  The difference between the two is that, in the case according to FIG. 4A, a diagnosis without leakage is made in both the first diagnosis stage and the second diagnosis stage, whereas in the case according to FIG. This is the point that a diagnosis with a leak is made in the second diagnosis stage.

  Specifically, in the case according to FIG. 4C, the evaporated fuel processing apparatus 11 according to the embodiment of the present invention did not obtain a leak-free diagnosis result at the second diagnosis stage at time t16 shown in FIG. 4C. In this case, a diagnosis is made that the evaporative fuel sealing system is leaking and abnormal (NG state). Then, at the same time t16, the leak diagnosis flag indicating the leak diagnosis result shifts from the hold state to the NG state, and thereafter maintains the NG state (see FIG. 4C (d)).

  In the evaporated fuel processing apparatus 11 according to the embodiment of the present invention, the integrated leak diagnosis is performed according to the procedure based on FIG. 2B, as in the case according to FIG. 4A. Specifically, in this integrated leak diagnosis, in the second diagnosis stage, leak diagnosis using the DTM method and the DDP method is performed in addition to the leak diagnosis using the PFD method, starting at time t14. When leak diagnosis results by the PFD method, DTM method, and DDP method are obtained, in principle, the leak diagnosis result by the DTM method is preferentially adopted as the integrated leak diagnosis result, while the leak diagnosis result by the DDP method is used as the DTM method. This is secondarily adopted as the integrated leak diagnosis result when the leak diagnosis result is pending (including inability to diagnose).

  In the case according to FIG. 4A, the evaporative fuel processing apparatus 11 (diagnostic unit 53) according to the embodiment of the present invention diagnoses that the evaporative fuel sealing system has a leak abnormality (NG state) by the leak diagnosis according to the DTM method. Suppose that As a result, in accordance with the principle of preferentially adopting the leak diagnosis result by the DTM method as the integrated leak diagnosis result, the evaporative fuel processing system 11 (diagnosis unit 53) according to the embodiment of the present invention has a leak in the evaporative fuel sealing system. Make a diagnosis of abnormality (NG state).

[Effect of Evaporative Fuel Processing Device 11 According to Embodiment of the Present Invention]
Next, the operation and effect of the evaporated fuel processing apparatus 11 according to the embodiment of the present invention will be described.
An evaporative fuel processing apparatus 11 based on a first aspect according to an embodiment of the present invention is mounted on a vehicle equipped with an internal combustion engine 13 and contains a fuel tank 15, a communication path connecting the fuel tank 15 and the atmosphere ( The evaporative fuel discharge passage 25 and the atmospheric flow passage 26) are provided in a canister 17 for recovering the evaporated fuel discharged from the fuel tank 15 through the communication passages 25 and 26, and a communication passage 26 connecting the canister 17 and the atmosphere. An air opening / closing valve 29 provided to open or close the canister 17 with respect to the atmosphere, a tank internal pressure sensor (tank internal pressure detecting unit) 27 for detecting the tank internal pressure Ptank of the fuel tank 15, and an air opening / closing valve 29 to open or close. And a diagnostic unit 53 that performs leak diagnosis of the evaporative fuel sealing system including the fuel tank 15.

  In the fuel vapor processing apparatus 11 based on the first aspect, the diagnostic unit 53 determines that the tank internal pressure is maintained when the atmospheric on-off valve 29 is in a closed state in accordance with a closing command from the control unit 55 after the ignition switch 43 of the vehicle is turned off. The detection unit 27 performs a leak diagnosis of the fuel vapor sealing system using a double differential method (DDP method) based on a correlation parameter related to a double differential value of the tank internal pressure Ptank, and a tank internal pressure sensor (tank internal pressure detection unit) 27. The leak diagnosis of the evaporative fuel seal system using the stagnation time method (DTM method) based on the relationship between the tank internal pressure Ptank and the stagnation time of the tank pressure Ptank is performed, and the leak diagnosis result using the stagnation time method is differentiated twice A configuration that is used preferentially with respect to a leak diagnosis result using the method may be adopted.

  In the evaporative fuel processing apparatus 11 based on the first aspect, the double differential method is used for the leak diagnosis result using the stagnation time method (DTM method) having higher diagnostic accuracy than the double differential method (DDP method). This is used preferentially for the leak diagnosis result. Specifically, for example, when the leak diagnosis result using the stagnation time method is normal without leak, the diagnosis unit 53 is normal without leak regardless of whether the leak diagnosis result using the twice differential method is normal. Make a diagnosis to the effect.

  According to the evaporated fuel processing apparatus 11 based on the first aspect, the leak diagnosis result using the stagnation time method (DTM method) having higher diagnostic accuracy than the two-time differential method (DDP method) Since it is preferentially used for the leak diagnosis result using the (DDP method), for example, even when applied to a hybrid vehicle, the leak diagnosis of the evaporated fuel sealing system can be performed with high accuracy.

  The evaporated fuel processing apparatus 11 based on the second aspect is the evaporated fuel processing apparatus 11 based on the first aspect, and the diagnosis time for obtaining the leak diagnosis result using the stagnation time method (DTM method) is You may employ | adopt the structure set as long time length compared with the diagnostic time for obtaining the leak diagnostic result using a twice differential method (DDP method).

  According to the evaporated fuel processing apparatus 11 based on the second aspect, it is possible to appropriately perform a leak diagnosis using a stagnation time method (DTM method) that requires a longer diagnosis time than the two-time differential method (DDP method). Therefore, the leakage diagnosis of the evaporated fuel sealing system can be performed with higher accuracy.

The evaporated fuel processing apparatus 11 based on the third aspect is the evaporated fuel processing apparatus 11 based on the first or second aspect, and the diagnosis unit 53 performs control after the ignition switch 43 of the vehicle is turned off. Based on the relationship between the tank internal pressure Ptank by the tank internal pressure sensor (tank internal pressure detection unit) 27 and a predetermined first threshold value P_th1 in the first diagnosis stage in which the atmospheric on-off valve 29 is in a closed state in accordance with the close command of the unit 55 A second diagnosis stage in which the first leak diagnosis using the PFD method (pressure fluctuation detection method) is performed and, after the first leak diagnosis, the atmospheric on-off valve 29 is in a closed state in accordance with a closing command of the control unit 55 , The pressure fluctuation detection method based on the relationship between the tank internal pressure Ptank and the predetermined second threshold P_th2 by the tank internal pressure sensor (tank internal pressure detector) 27 PFD method), the second derivative method (DDP method), and performs the second leak diagnosis using the dwell time method (DTM) method.
The atmospheric on-off valve 29 is opened once after the first leak diagnosis is completed according to the opening command of the control unit 55. The diagnosis unit 53 uses the second differential method (DDP method) or the stagnation time method (DTM method) when the result of the second leak diagnosis using the pressure fluctuation detection method (PFD method) is abnormal with leakage. Regardless of the result of the leak diagnosis of 2, the diagnosis that there is an abnormality with a leak is made.

  Here, the pressure fluctuation detection method (PFD method) is preferably used to detect a leak hole having a relatively large diameter, while the double differential method (DDP method) or the stagnation time method (DTM method) It is preferably used for detecting a leak hole having a small diameter. Therefore, even if the result of the second leak diagnosis using the pressure fluctuation detection method (PFD method) is normal without leak, there is a possibility that a leak hole having a relatively small diameter is actually vacant.

  Therefore, even when the result of the second leak diagnosis using the pressure fluctuation detection method (PFD method) is normal without leak, the double differential method (DDP method) or the stagnation time method (DTM method) was used. The second leak diagnosis is always performed. However, if the result of the second leak diagnosis using the pressure fluctuation detection method (PFD method) is abnormal with a leak, the second differential method (DDP method) or the stagnation time method (DTM method) is used. It is not always necessary to perform the leak diagnosis.

  In the evaporated fuel processing apparatus 11 based on the third aspect, the diagnosis unit 53 performs the second differential method (DDP method) when the result of the second leak diagnosis using the pressure fluctuation detection method (PFD method) is abnormal with a leak. Regardless of the result of the second leak diagnosis using the stagnation time method (DTM method), the leak diagnosis of the evaporative fuel sealing system should be performed in a short time in order to make a diagnosis that there is a leak abnormality Can do.

Further, in the fuel vapor processing apparatus 11 based on the fourth aspect, the diagnosis unit 53 is the first in which the atmospheric on-off valve 29 is in a closed state in accordance with the closing command of the control unit 55 after the ignition switch 43 of the vehicle is turned off. In the diagnosis stage, the first leak diagnosis using the PFD method (pressure fluctuation detection method) is performed based on the relationship between the tank internal pressure Ptank by the tank internal pressure sensor (tank internal pressure detection unit) 27 and a predetermined first threshold value P_th1. In addition, after the end of the first leak diagnosis, in the second diagnosis stage in which the atmospheric on-off valve 29 is in a closed state according to the closing command of the control unit 55, the tank internal pressure Ptank and the tank internal pressure sensor (tank internal pressure detecting unit) 27 A second leak diagnosis using a PFD method (pressure fluctuation detection method) is performed based on a predetermined second threshold value P_th2.
The atmospheric on-off valve 29 is opened once after the first leak diagnosis is completed according to the opening command of the control unit 55. The first threshold value P_th1 used in the first diagnosis stage is set to have a larger deviation from the atmospheric pressure than the second threshold value P_th2 used in the second diagnosis stage.

  In the fuel vapor processing apparatus 11 based on the fourth aspect, after the ignition switch 43 of the vehicle is turned off, when performing a leak diagnosis using the PFD method (pressure fluctuation detection method) in two stages, the ignition switch 43 The first threshold value P_th1 used in the first diagnosis stage in which the influence of the residual heat on the internal combustion engine 13 and the exhaust system of the internal combustion engine 13 remains strong compared to the second diagnosis stage after turning off is set in the second diagnosis stage. The deviation from the atmospheric pressure is set larger than the second threshold value P_th2 used.

  Therefore, according to the evaporated fuel processing apparatus 11 based on the fourth aspect, the dynamic range (vibration width) of the tank internal pressure Ptank by the tank internal pressure sensor (tank internal pressure detection unit) 27 in each of the first and second diagnostic stages is obtained. In consideration, since the first and second threshold values P_th1 and P_th2 are appropriately set, for example, even when applied to a hybrid vehicle, the leakage diagnosis of the evaporated fuel sealing system can be performed with high accuracy. it can.

  Further, the evaporated fuel processing apparatus 11 based on the fifth aspect is the evaporated fuel processing apparatus 11 based on the fourth aspect, wherein the tank internal pressure Ptank is the ignition during the first diagnosis period according to the first diagnosis stage. Adopting a configuration that is a stabilization time that is expected to be stable compared to immediately after the switch 43 is turned off, and is set to a shorter time length than the second diagnosis period according to the second diagnosis stage. Also good.

  In the evaporative fuel processing device 11 based on the fifth aspect, after the ignition switch 43 of the vehicle is turned off, when performing a leak diagnosis in two stages, the internal combustion engine 13 and the internal combustion engine 13 of the internal combustion engine 13 are turned off after the ignition switch 43 is turned off. The first diagnosis period dt1 related to the first diagnosis stage in which the influence of the residual heat related to the exhaust system remains stronger than that in the second diagnosis stage is shorter than the second diagnosis period dt2 related to the second diagnosis stage. Set to time length.

  Therefore, according to the evaporated fuel processing device 11 based on the fifth aspect, the time change rate of the tank internal pressure Ptank by the tank internal pressure sensor (tank internal pressure detection unit) 27 in each of the first and second diagnosis stages is taken into consideration. Since the lengths of the first and second diagnosis periods dt1 and dt2 are appropriately set, the leakage diagnosis accuracy of the evaporated fuel sealing system is improved compared to the evaporated fuel processing apparatus 11 based on the first aspect. This can be further improved.

  Further, the evaporated fuel processing device 11 based on the sixth aspect is the evaporated fuel processing device 11 based on the fourth or fifth aspect, in which the atmospheric on-off valve 29 is in accordance with the opening command from the control unit 55 in accordance with the first leak. The diagnosis unit 53 is opened once immediately after completion of the diagnosis, and the diagnosis unit 53 starts the second diagnosis immediately after the atmospheric on-off valve 29 is switched from the open state to the closed state in accordance with the closing command of the control unit 55. May be.

  In the fuel vapor processing apparatus 11 based on the sixth aspect, the atmospheric on-off valve 29 is temporarily opened immediately after the end of the first leak diagnosis in accordance with the opening command of the control unit 55, and the diagnosis unit 53 receives the closing command of the control unit 55. Therefore, immediately after the atmospheric on / off valve 29 is switched from the open state to the closed state, the second diagnosis is started without using wasted time, so compared to the evaporated fuel processing device 11 based on the fourth or fifth aspect. The leak diagnosis of the evaporated fuel sealing system can be performed in a short time with higher accuracy.

[Other Embodiments]
The plurality of embodiments described above show examples of realization of the present invention. Therefore, the technical scope of the present invention should not be limitedly interpreted by these. This is because the present invention can be implemented in various forms without departing from the gist or main features thereof.

  For example, in the embodiment according to the present invention, the example in which the temperature in the evaporative fuel sealing system after the ignition switch 43 is turned off has been described as being high temperature, but the present invention is not limited to this example. The present invention can also be applied to a case where the temperature in the evaporated fuel sealing system after the ignition switch 43 is turned off changes to a low temperature (for example, less than zero degrees Celsius). In the case where the temperature in the fuel vapor sealed system after the ignition switch 43 is turned off changes to the low temperature side, the tank internal pressure in the sealed state becomes negative through the liquefaction (condensation) of the fuel vapor accumulated in the fuel tank 15. Become. In such a case, the present invention may be implemented with appropriate modifications according to an embodiment in which the tank internal pressure in a sealed state is positive.

  In the embodiment according to the present invention, an example in which the evaporated fuel processing apparatus 11 according to the embodiment of the present invention is applied to a hybrid vehicle including the internal combustion engine 13 and the electric motor as drive sources has been described. The present invention is not limited to this example. Needless to say, the present invention may be applied to a vehicle having only the internal combustion engine 13 as a power source.

DESCRIPTION OF SYMBOLS 11 Evaporated fuel processing apparatus 13 Internal combustion engine 15 Fuel tank 17 Canister 25 Evaporated fuel discharge path (communication path)
26 Large airflow passage (communication passage)
27 Tank pressure sensor (tank pressure detector)
29 Atmospheric open / close valve (open / close valve)
43 Ignition switch 53 Diagnosis unit 55 Control unit P_th1 First threshold value P_th2 Second threshold value

Claims (3)

A fuel tank mounted on a vehicle equipped with an internal combustion engine and containing fuel;
A canister that is provided in a communication path that connects between the fuel tank and the atmosphere, and that collects the evaporated fuel discharged from the fuel tank via the communication path;
An on-off valve provided in a communication path connecting the canister and the atmosphere, and opening or closing the canister to the atmosphere;
A tank internal pressure detector for detecting the tank internal pressure of the fuel tank;
A control unit that issues a command to open or close the on-off valve;
A diagnostic unit for performing a leak diagnosis of an evaporative fuel sealing system including the fuel tank;
With
The diagnostic unit
After the ignition switch of the vehicle is turned off, when the on-off valve is in a closed state according to the command of the control unit,
While performing a leak diagnosis of the evaporative fuel sealing system using a double differential method based on a correlation parameter related to a double differential value of the tank internal pressure by the tank internal pressure detection unit,
Leak diagnosis of the evaporative fuel sealing system using the stagnation time method based on the relationship between the tank pressure by the tank pressure detector and the stagnation time of the tank pressure,
The leak diagnosis result using the stagnation time method is preferentially used with respect to the leak diagnosis result using the twice differential method,
The evaporative fuel processing apparatus characterized by the above-mentioned. It is an evaporative fuel processing apparatus of Claim 1, Comprising:
The diagnosis time for obtaining the leak diagnosis result using the stagnation time method is set to a longer time length than the diagnosis time for obtaining the leak diagnosis result using the twice-differential method,
The evaporative fuel processing apparatus characterized by the above-mentioned. The evaporative fuel processing apparatus according to claim 1 or 2,
In the first diagnosis stage in which the on-off valve is in a closed state in accordance with the command from the control unit after the ignition switch of the vehicle is turned off, the diagnosis unit determines the tank internal pressure and the tank internal pressure by the tank internal pressure detection unit in advance. In the second diagnosis stage in which the first leak diagnosis is performed based on the relationship of the first threshold, and after the first leak diagnosis, the on-off valve is in a closed state in accordance with the command of the control unit, Performing a second leak diagnosis using the pressure fluctuation detection method based on the relationship between the tank internal pressure by the tank internal pressure detection unit and a predetermined second threshold, the second derivative method, and the stagnation time method;
The on-off valve is opened once after completion of the first leak diagnosis according to the command of the control unit,
If the result of the second leak diagnosis using the pressure fluctuation detection method is abnormal with a leak, the diagnosis unit determines whether the result of the second leak diagnosis using the second differential method or the stagnation time method is used. Regardless, make a diagnosis of leaking and abnormal,
The evaporative fuel processing apparatus characterized by the above-mentioned.

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