Patent Publication Number: US-2023160360-A1

Title: Leakage diagnostic device, and vehicle

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021- 191331 filed on Nov. 25, 2021, incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The disclosure relates to a leakage diagnostic device and a vehicle. 
     2. Description of Related Art 
     A fuel supply system described in Japanese Unexamined Patent Application Publication No. 2013-087661 (JP 2013-087661 A) includes a fuel tank, a vapor passage, a canister, an outside air passage, and a shut-off valve. The fuel tank stores fuel. The canister is connected to the fuel tank via the vapor passage. The canister is able to adsorb evaporated fuel generated in the fuel tank. The outside air passage is connected to the canister. The shut-off valve is located in the middle of the vapor passage. The shut-off valve opens and closes the flow channel of the vapor passage. 
     The leakage diagnostic device described in JP 2013-087661 A performs a leakage diagnosis of the fuel tank during a stop of an internal combustion engine. Specifically, the leakage diagnostic device described in JP 2013-087661 A emits gas from the fuel tank by opening the shut-off valve. Then, the leakage diagnostic device described in JP 2013-087661 A performs a leakage diagnosis of the fuel tank based on a change in index value that indicates a pressure in the fuel tank. The leakage diagnostic device described in JP 2013-087661 A limits the number of times a leakage diagnosis is performed to a predetermined allowable number of times in a period from when the internal combustion engine stops to when the internal combustion engine restarts. With this configuration, emission of an excessive amount of evaporated fuel is suppressed as a result of leakage diagnosis. 
     SUMMARY 
     In the fuel supply system described in JP 2013-087661 A, even when a leakage diagnosis is not performed, gas containing evaporated fuel can move from the fuel tank to the canister via the vapor passage during a stop of the internal combustion engine. When gas containing evaporated fuel moves in this way, the amount of evaporated fuel adsorbed by the canister increases. As a result, in the fuel supply system described in JP 2013-087661 A, even when the number of times a leakage diagnosis is performed during a stop of the internal combustion engine is less than the allowable number of times, there is a possibility that evaporated fuel is not able to be adsorbed by the canister any more. If a leakage diagnosis is performed in a state where evaporated fuel is not able to be adsorbed by the canister, gas containing evaporated fuel in the fuel tank is undesirably emitted to the outside. 
     An aspect of the disclosure relates to a leakage diagnostic device. The leakage diagnostic device includes circuitry configured to perform a diagnosis of a fuel supply system. The fuel supply system includes a fuel tank configured to store fuel, a vapor passage connected to the fuel tank, a canister connected to the vapor passage and configured to be able to adsorb evaporated fuel generated in the fuel tank, an outside air passage connected to the canister, and a shut-off valve configured to open and close a flow channel of the vapor passage. The circuitry is configured to execute an emission process of, on condition that the number of times a leakage diagnosis of the fuel tank is performed in a stop period from when an internal combustion engine stops to when the internal combustion engine restarts is less than a predetermined allowable number of times, emitting gas from the fuel tank via the canister by opening the shut-off valve, a diagnosis process of performing the leakage diagnosis based on a change in index value, caused by the emission process, the index value indicating a pressure in the fuel tank, and a subtraction process of, when fuel has been fed to the fuel tank in a state where the shut-off valve is open in the stop period of the internal combustion engine, reducing the allowable number of times in the stop period in which fuel has been fed to the fuel tank. 
     With the above configuration, when gas containing evaporated fuel is pushed out from the fuel tank as a result of feeding fuel to the fuel tank and the amount of evaporated fuel adsorbed by the canister increases, the allowable number of times is reduced. Thus, after feeding fuel, the number of times a leakage diagnosis is performed is further strictly limited. This reduces a situation in which a leakage diagnosis is performed regardless of the fact that the amount of evaporated fuel that is able to be adsorbed by the canister is small and, as a result, gas containing evaporated fuel is emitted to the outside. 
     In the above configuration, in the subtraction process, the circuitry may be configured to increase an amount of subtraction of the allowable number of times when a large amount of fuel is fed to the fuel tank in the stop period as compared to the amount of subtraction of the allowable number of times when a small amount of fuel is fed to the fuel tank in the stop period. 
     With the above configuration, when there is a large amount of fuel fed to the fuel tank, that is, when the amount of evaporated fuel that is pushed out from the fuel tank is large, the allowable number of times is reduced by a larger amount. Therefore, the amount of evaporated fuel adsorbed by the canister is able to be further accurately reflected in the allowable number of times. 
     Another aspect of the disclosure relates to a vehicle. The vehicle includes an internal combustion engine serving as a driving source of the vehicle, a motor generator serving as a driving source of the vehicle, a battery configured to supply electric power to the motor generator, a fuel supply system configured to supply fuel to the internal combustion engine, and a leakage diagnostic device configured to perform a diagnosis of the fuel supply system. The fuel supply system includes a fuel tank configured to store fuel, a vapor passage connected to the fuel tank, a canister connected to the vapor passage and configured to be able to adsorb evaporated fuel generated in the fuel tank, an outside air passage connected to the canister, and a shut-off valve configured to open and close a flow channel of the vapor passage. The leakage diagnostic device is configured to execute an emission process of, on condition that the number of times a leakage diagnosis of the fuel tank is performed in a stop period from when the internal combustion engine stops to when the internal combustion engine restarts is less than a predetermined allowable number of times, emitting gas from the fuel tank via the canister by opening the shut-off valve, a diagnosis process of performing the leakage diagnosis based on a change in index value, caused by the emission process, the index value indicating a pressure in the fuel tank, and a subtraction process of, when fuel has been fed to the fuel tank in a state where the shut-off valve is open in the stop period of the internal combustion engine, reducing the allowable number of times in the stop period in which fuel has been fed to the fuel tank. 
     With the above vehicle, the vehicle can be driven by using the driving force of only the motor generator, so there are many opportunities that the internal combustion engine stops. With an increase in opportunity to stop the internal combustion engine, an opportunity to perform a leakage diagnosis increases. In addition, an opportunity to feed fuel in a state where the internal combustion engine is stopped and then cause the vehicle to run and stop in a state where the internal combustion engine is stopped also increases. In this way, it is suitable to apply the above-described leakage diagnostic device to a vehicle in which there are many opportunities to perform a leakage diagnosis and there are many opportunities to feed fuel during a stop of the internal combustion engine. 
     In the above configuration, the battery may be chargeable from an external power supply provided outside the vehicle. The above vehicle, that is, a so-called plug-in hybrid electric vehicle, generally includes a large-capacity battery, so one-time stop period of the internal combustion engine tends to be long. As a result, the number of times a leakage diagnosis is performed in a one stop period of the internal combustion engine tends to increase. Therefore, it is suitable to apply the above-described leakage diagnostic device to the above vehicle. 
     Further another aspect of the disclosure relates to a leakage diagnostic device. The leakage diagnostic device includes circuitry configured to perform a diagnosis of a fuel supply system. The fuel supply system includes a fuel tank configured to store fuel, a vapor passage connected to the fuel tank, a canister connected to the vapor passage and configured to be able to adsorb evaporated fuel generated in the fuel tank, an outside air passage connected to the canister, and a shut-off valve configured to open and close a flow channel of the vapor passage. The circuitry is configured to execute an emission process of, on condition that the number of times a leakage diagnosis of the fuel tank is performed in a stop period from when an internal combustion engine stops to when the internal combustion engine restarts is less than a predetermined allowable number of times, emitting gas from the fuel tank via the canister by opening the shut-off valve, a diagnosis process of performing the leakage diagnosis based on a change in index value, caused by the emission process, the index value indicating a pressure in the fuel tank, and a subtraction process of, when the pressure in the fuel tank is higher than an atmospheric pressure and the shut-off valve is opened in the stop period of the internal combustion engine, reducing the allowable number of times in the stop period while the shut-off valve is open. 
     With the above configuration, when gas containing evaporated fuel is pushed out from the fuel tank due to a high pressure in the fuel tank and the amount of evaporated fuel adsorbed by the canister increases, the allowable number of times is reduced. Thus, the number of times a leakage diagnosis is performed is further strictly limited. This reduces a situation in which a leakage diagnosis is performed regardless of the fact that the amount of evaporated fuel that is able to be adsorbed by the canister is small and, as a result, gas containing evaporated fuel is emitted to the outside. 
     In the above configuration, in the subtraction process, the circuitry may be configured to increase an amount of subtraction of the allowable number of times when there is a large difference between the pressure in the fuel tank and the atmospheric pressure in the stop period as compared to an amount of subtraction of the allowable number of times when there is a small difference between the pressure in the fuel tank and the atmospheric pressure in the stop period. 
     With the above configuration, when there is a large difference between a pressure in the fuel tank and an atmospheric pressure, that is, when a large amount of evaporated fuel is pushed out from the fuel tank, the allowable number of times is reduced by a larger amount. Therefore, the amount of evaporated fuel adsorbed by the canister is able to be further accurately reflected in the allowable number of times. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the disclosure will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein: 
         FIG.  1    is a schematic diagram showing the schematic configuration of a vehicle; 
         FIG.  2    is a diagram showing the configuration of an internal combustion engine and the like; and 
         FIG.  3    is a flowchart showing leakage diagnosis control. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Schematic Configuration of Vehicle 
     Hereinafter, an embodiment of the disclosure will be described with reference to  FIG.  1    to  FIG.  3   . First, the schematic configuration of a vehicle  100  will be described. 
     As shown in  FIG.  1   , the vehicle  100  includes a spark-ignition internal combustion engine  10 . The vehicle  100  further includes a first motor generator  71  and a second motor generator  72  each of which has the function of both an electric motor and a generator. Therefore, the vehicle  100  is a so-called hybrid electric vehicle. In the present embodiment, each of the internal combustion engine  10 , the first motor generator  71 , and the second motor generator  72  is a driving source of the vehicle  100 . 
     The vehicle  100  includes a first planetary gear train  40 , a ring gear shaft  45 , a second planetary gear train  50 , a speed reduction mechanism  62 , a differential mechanism  63 , and a plurality of drive wheels  64 . The first planetary gear train  40  includes a sun gear  41 , a ring gear  42 , a plurality of pinion gears  43 , and a carrier  44 . The sun gear  41  is an external gear. The sun gear  41  is connected to the first motor generator  71 . The ring gear  42  is an internal gear and is located coaxially with the sun gear  41 . Each of the pinion gears  43  is located between the sun gear  41  and the ring gear  42 . Each of the pinion gears  43  is in mesh with both the sun gear  41  and the ring gear  42 . The carrier  44  supports the pinion gears  43 . The pinion gears  43  each are rotatable on its axis and revolvable by rotating together with the carrier  44 . The carrier  44  is connected to a crankshaft  14  of the internal combustion engine  10 . Therefore, the first motor generator  71  is coupled to the crankshaft  14  of the internal combustion engine  10  via the first planetary gear train  40 . 
     When the driving force of the internal combustion engine  10  is input to the carrier  44 , the driving force of the internal combustion engine  10  is distributed between the sun gear  41  side and the ring gear  42  side. When the driving force of the internal combustion engine  10 , transmitted via the sun gear  41 , is input to the rotary shaft of the first motor generator  71 , the first motor generator  71  functions as a generator. 
     On the other hand, when the first motor generator  71  is caused to function as an electric motor, the driving force of the first motor generator  71  is input to the sun gear  41 . As a result, the driving force of the first motor generator  71 , input to the sun gear  41 , is distributed between the carrier  44  side and the ring gear  42  side. When the driving force of the first motor generator  71 , transmitted via the carrier  44 , is input to the crankshaft  14  of the internal combustion engine  10 , the crankshaft  14  of the internal combustion engine  10  rotates. 
     The ring gear shaft  45  is connected to the ring gear  42 . The ring gear shaft  45  is also connected to the drive wheels  64  via the speed reduction mechanism  62  and the differential mechanism  63 . The speed reduction mechanism  62  reduces the rotation speed of the ring gear shaft  45  and outputs the rotation. The differential mechanism  63  allows a rotation speed difference between the right and left drive wheels  64 . 
     The second planetary gear train  50  includes a sun gear  51 , a ring gear  52 , a plurality of pinion gears  53 , a carrier  54 , and a case  55 . The sun gear  51  is an external gear. The sun gear  51  is connected to the second motor generator  72 . The ring gear  52  is an internal gear and is located coaxially with the sun gear  51 . The ring gear  52  is connected to the ring gear shaft  45 . Each of the pinion gears  53  is located between the sun gear  51  and the ring gear  52 . Each of the pinion gears  53  is in mesh with both the sun gear  51  and the ring gear  52 . The carrier  54  supports the pinion gears  53 . The pinion gears  53  each are rotatable on its axis. The carrier  54  is fixed to the case  55 . Therefore, the pinion gears  53  are not revolvable. 
     The second motor generator  72  is capable of functioning as a generator at the time of decelerating the vehicle  100  to cause the vehicle  100  to generate regenerative braking force according to the amount of electric power generated by the second motor generator  72 . 
     On the other hand, when the second motor generator  72  functions as an electric motor, the driving force of the second motor generator  72  is input to the drive wheels  64  via the second planetary gear train  50 , the ring gear shaft  45 , the speed reduction mechanism  62 , and the differential mechanism  63 . As a result, the drive wheels  64  rotate by using the driving force of the second motor generator  72 . 
     The vehicle  100  includes a battery  75 , a first inverter  76 , and a second inverter  77 . The first inverter  76  performs alternating-current and direct-current power conversion between the first motor generator  71  and the battery  75 . The first inverter  76  adjusts the amount of electric power exchanged between the first motor generator  71  and the battery  75 . The second inverter  77  performs alternating-current and direct-current power conversion between the second motor generator  72  and the battery  75 . The second inverter  77  adjusts the amount of electric power exchanged between the second motor generator  72  and the battery  75 . 
     The vehicle  100  includes a converter  78  and an inlet  79 . The inlet  79  is able to connect with an external power supply  200  (described later). In other words, the vehicle  100  is a so-called plug-in hybrid electric vehicle. The inlet  79  is electrically connected to the battery  75  via the converter  78 . Alternating-current power is supplied from the external power supply  200  to the inlet  79 . The converter  78  converts alternating-current power, supplied from the inlet  79 , to direct-current power. The converter  78  supplies the converted direct-current power to the battery  75 . As a result, the battery  75  is charged from the external power supply  200 . In other words, the battery  75  is chargeable from the external power supply  200  provided outside the vehicle  100 . 
     Configuration of Internal Combustion Engine 
     As shown in  FIG.  2   , the internal combustion engine  10  includes a plurality of cylinders  11 , an intake passage  15 , and an exhaust passage  21 . Each of the cylinders  11  is a space in which air-fuel mixture of fuel and intake air combusts. The internal combustion engine  10  includes four cylinders  11 .  FIG.  2    shows only one cylinder  11 . The intake passage  15  is connected to the cylinders  11 . The intake passage  15  introduces intake air from outside the internal combustion engine  10  into the cylinders  11 . The exhaust passage  21  is connected to the cylinders  11 . The exhaust passage  21  emits exhaust gas from the cylinders  11  to outside the internal combustion engine  10 . 
     The internal combustion engine  10  includes a plurality of pistons  12 , a plurality of connecting rods  13 , the crankshaft  14 , a throttle valve  16 , a plurality of fuel injection valves  17 , and a plurality of ignition devices  19 . The throttle valve  16  is located in the middle of the intake passage  15 . The throttle valve  16  adjusts the amount of intake air flowing through the intake passage  15 . Each of the fuel injection valves  17  is located near an associated one of the cylinders  11  in the intake passage  15 . The internal combustion engine  10  includes four fuel injection valves  17 , one for each of the four cylinders  11 . Each of the fuel injection valves  17  injects fuel toward an associated one of the cylinders  11 . Each of the ignition devices  19  is located near an associated one of the cylinders  11 . The internal combustion engine  10  includes four ignition devices  19 , one for each of the four cylinders  11 . The ignition devices  19  ignite air-fuel mixture of fuel and intake air by using spark discharge. 
     Each of the pistons  12  is located in an associated one of the cylinders  11 . The internal combustion engine  10  includes four pistons  12 , one for each of the four cylinders  11 . Each of the pistons  12  is coupled to the crankshaft  14  via an associated one of the connecting rods  13 . Each of the pistons  12  reciprocates as a result of combustion of air-fuel mixture of fuel and intake air in an associated one of the cylinders  11 . As a result of reciprocation of the pistons  12 , the crankshaft  14  rotates. 
     Configuration of Fuel Supply System 
     The vehicle  100  further includes a fuel supply system  25 . The fuel supply system  25  includes a fuel tank  26 , a feed pump  27 , a fuel passage  28 , and a lid door  29 . The fuel tank  26  includes a tank body  26 A and a cap  26 C. The tank body  26 A is able to store fuel. The tank body  26 A includes a fill opening  26 B for feeding fuel to the tank body  26 A. The cap  26 C closes the fill opening  26 B of the tank body  26 A. The cap  26 C is detachable from the tank body  26 A. The feed pump  27  is located in the tank body  26 A of the fuel tank  26 . The feed pump  27  connects with the fuel injection valves  17  via the fuel passage  28 . Therefore, the feed pump  27  supplies fuel to the fuel injection valves  17  via the fuel passage  28 . The lid door  29  makes up part of the exterior of the vehicle  100 . The lid door  29  is located near the cap  26 C. The lid door  29  is able to be opened and closed by operation of a driver or the like. In a state where the lid door  29  is closed, the lid door  29  covers the cap  26 C. 
     The fuel supply system  25  includes a vapor passage  31 , a canister  32 , an outside air passage  33 , a purge passage  34 , a shut-off valve  36 , an outside air valve  37 , a purge valve  38 , and a pump module  39 . The canister  32  is able to adsorb evaporated fuel generated in the fuel tank  26 . A first end of the vapor passage  31  is connected to the canister  32 . A second end of the vapor passage  31  is located in the fuel tank  26 . The shut-off valve  36  is located in the middle of the vapor passage  31 . The shut-off valve  36  switches the flow channel of the vapor passage  31  to any one of an open state and a closed state. The shut-off valve  36  is a normally-closed electromagnetic valve. 
     A first end of the outside air passage  33  is connected to the canister  32 . A second end of the outside air passage  33  is open to outside the vehicle  100 . The outside air valve  37  is located in the middle of the outside air passage  33 . The outside air valve  37  switches the flow channel of the outside air passage  33  to any one of an open state and a closed state. The outside air valve  37  is a normally-open electromagnetic valve. The pump module  39  is located in the middle of the outside air passage  33 . The pump module  39  is connected to the outside air valve  37 . The pump module  39  is able to emit gas from the fuel tank  26  to the outside via the vapor passage  31 , the canister  32 , and the outside air passage  33 . 
     A first end of the purge passage  34  is connected to the canister  32 . A second end of the purge passage  34  is connected to a downstream-side part of the intake passage  15  when viewed from the throttle valve  16 . The purge valve  38  is located in the middle of the purge passage  34 . The purge valve  38  is able to adjust the opening degree of the flow channel of the purge passage  34 . The purge valve  38  is a normally-closed electromagnetic valve. 
     Configuration of Sensor and Controller 
     As shown in  FIG.  2   , the vehicle  100  includes an accelerator operation amount sensor  81 , a vehicle speed sensor  82 , a pressure sensor  83 , a lid sensor  84 , a fuel level sensor  86 , an atmospheric pressure sensor  87 , and a display  89 . The accelerator operation amount sensor  81  detects an accelerator operation amount ACC that is the operation amount of an accelerator pedal operated by the driver. The vehicle speed sensor  82  detects a vehicle speed SP that is the speed of the vehicle  100 . The pressure sensor  83  is attached to the top part of the fuel tank  26 . The pressure sensor  83  detects a tank internal pressure PT that is a pressure in the fuel tank  26 . The lid sensor  84  detects an open-close position LS that is the position of the lid door  29 . The fuel level sensor  86  is located in the fuel tank  26 . The fuel level sensor  86  detects a fuel level FL that is the level of fuel in the fuel tank  26 . The atmospheric pressure sensor  87  detects an atmospheric pressure PA that is the pressure of the atmosphere at a point where the vehicle  100  is located. The display  89  is located near the driver seat of the vehicle  100 . The display  89  displays visual information to the driver or the like of the vehicle  100 . 
     The vehicle  100  includes a controller  90 . The controller  90  acquires a signal indicating an accelerator operation amount ACC from the accelerator operation amount sensor  81 . The controller  90  acquires a signal indicating a vehicle speed SP from the vehicle speed sensor  82 . The controller  90  acquires a signal indicating a tank internal pressure PT from the pressure sensor  83 . The controller  90  acquires a signal indicating an open-close position LS from the lid sensor  84 . The controller  90  acquires a signal indicating a fuel level FL from the fuel level sensor  86 . In other words, the controller  90  is able to detect the amount of fuel in the fuel tank  26  and the amount of fuel fed to the fuel tank  26  based on the fuel level FL. The controller  90  acquires a signal indicating an atmospheric pressure PA from the atmospheric pressure sensor  87 . The controller  90  causes the display  89  to display visual information by outputting a control signal to the display  89 . 
     The controller  90  calculates a vehicle required driving force based on an accelerator operation amount ACC and a vehicle speed SP. A vehicle required driving force is a required value of driving force needed for the vehicle  100  to run. The controller  90  determines a torque distribution among the internal combustion engine  10 , the first motor generator  71 , and the second motor generator  72  based on the vehicle required driving force. The controller  90  controls the output of the internal combustion engine  10  and the motoring and regeneration of each of the first motor generator  71  and the second motor generator  72  based on the torque distribution among the internal combustion engine  10 , the first motor generator  71 , and the second motor generator  72 . Specifically, the controller  90  controls the opening degree of the throttle valve  16 , a fuel injection amount from each of the fuel injection valves  17 , the ignition timing of each of the ignition devices  19 , and the like by outputting a control signal to the internal combustion engine  10 . The controller  90  controls the first motor generator  71  via the first inverter  76  by outputting a control signal to the first inverter  76 . The controller  90  controls the second motor generator  72  via the second inverter  77  by outputting a control signal to the second inverter  77 . 
     The controller  90  executes introduction control to introduce evaporated fuel adsorbed by the canister  32  into the intake passage  15  while the internal combustion engine  10  is being driven. Specifically, the controller  90  opens the shut-off valve  36 , the outside air valve  37 , and the purge valve  38  while the internal combustion engine  10  is being driven. Then, outside air is introduced into the canister  32  via the outside air passage  33  due to negative pressure in the intake passage  15 . As a result, evaporated fuel adsorbed by the canister  32  and outside air are introduced into the intake passage  15  via the purge passage  34 . 
     The controller  90  executes preparation control to prepare for feeding fuel at the time of feeding fuel to the fuel tank  26 . Specifically, the controller  90  detects the status of the lid door  29  based on the open-close position LS. When the controller  90  detects that the lid door  29  is in an open state, the controller  90  closes the purge valve  38  and opens the shut-off valve  36  and the outside air valve  37 . Then, at the time of feeding fuel to the fuel tank  26 , gas in the fuel tank  26  is able to move from the fuel tank  26  to the canister  32 . As a result, at the time of feeding fuel to the fuel tank  26 , emission of gas from the fuel tank  26  via the fill opening  26 B of the fuel tank  26  to the outside is suppressed. 
     The controller  90  can be configured as circuitry including one or more processors that execute various processes in accordance with a computer program (software). The controller  90  may be configured as one or more dedicated hardware circuits, such as application-specific integrated circuits (ASICs), that execute at least part of the various processes, or circuitry including a combination of them. Each processor includes a CPU, and a memory, such as a RAM and a ROM. The memory stores program codes or instructions configured to cause the CPU to execute processes. The memory, that is, a computer-readable medium, includes any medium accessible by a general-purpose or special-purpose computer. 
     External Power Supply 
     As shown in  FIG.  1   , the external power supply  200  includes a power supply body  210 , a breaker  220 , and a connector  230 . The connector  230  is able to connect with the inlet  79 . The connector  230  is connected to the power supply body  210  via the breaker  220 . The breaker  220  is able to break electrical connection between the connector  230  and the power supply body  210 . The power supply body  210  is able to supply alternating-current power. 
     Leakage Diagnosis Control 
     Next, leakage diagnosis control that is executed by the controller  90  will be described. When the internal combustion engine  10  stops, the controller  90  executes leakage diagnosis control over the fuel tank  26 . In the present embodiment, the controller  90  is an example of a leakage diagnostic device. Hereinafter, a period from when the internal combustion engine  10  stops to when the internal combustion engine  10  restarts is referred to as a stop period of the internal combustion engine  10 . 
     As shown in  FIG.  3   , when the controller  90  starts leakage diagnosis control, the controller  90  proceeds with the process to step S 11 . In step S 11 , the controller  90  sets an initial value of an allowable number of times CA. The initial value of the allowable number of times CA is a predetermined value. An example of the initial value of the allowable number of times CA is  10 . Here, the allowable number of times CA is a value for limiting execution of leakage diagnosis in the current stop period. After that, the controller  90  proceeds with the process to step S 21 . 
     In step S 21 , the controller  90  determines whether a predetermined subtraction condition is satisfied. The subtraction condition is satisfied when at least one of the following condition (A) and condition (B) is satisfied. 
     Condition (A): Fuel has been fed to the fuel tank  26  in a current stop period. Condition (B): In a current stop period, there is a period during which the tank internal pressure PT is higher than the atmospheric pressure PA and the shut-off valve  36  is open. 
     In determining whether Condition (A) is satisfied, the controller  90  detects the amount of fuel in the fuel tank  26  based on the fuel level FL. When the amount of fuel in the fuel tank  26  is increased during the current stop period, the controller  90  determines that fuel has been fed to the fuel tank  26 . 
     In step S 21 , when the controller  90  determines that the subtraction condition is not satisfied (NO in S 21 ), the controller  90  proceeds with the process to step S 31 . On the other hand, in step S 21 , when the controller  90  determines that the subtraction condition is satisfied (YES in S 21 ), the controller  90  proceeds with the process to step S 22 . 
     In step S 22 , the controller  90  executes the subtraction process to subtract the allowable number of times CA in the current stop period. Specifically, when the controller  90  determines that Condition (A) is satisfied in the process of the last step S 21 , the controller  90  reduces the allowable number of times CA as follows. The controller  90  increases the amount of subtraction of the allowable number of times CA when a large amount of fuel has been fed to the fuel tank  26  in the current stop period as compared to when a small amount of fuel has been fed to the fuel tank  26  in the current stop period. The amount of subtraction is increased in a stepwise manner as the amount of fuel fed increases. For example, the amount of subtraction is set to one when the amount of fuel fed is less than 10 liters, and the amount of subtraction is set to two when the amount of fuel fed is greater than or equal to 10 liters and less than 20 liters. When the controller  90  determines that Condition (B) is satisfied in the process of the last step S 21 , the controller  90  reduces the allowable number of times CA as follows. The controller  90  increases the amount of subtraction of the allowable number of times CA when there is a large difference between the tank internal pressure PT and the atmospheric pressure PA at the time of the process of step S 22  as compared to when there is a small difference between the tank internal pressure PT and the atmospheric pressure PA at the time of the process of step S 22 . In this case as well, as in the case of the amount of fuel fed, the amount of subtraction is increased by one each time the difference between the tank internal pressure PT and the atmospheric pressure PA becomes larger than a set value. In this way, the controller  90  obtains a new allowable number of times CA by performing reduction based on the amount of fuel fed and the tank internal pressure PT from the allowable number of times CA at the beginning of step S 22 . After that, the controller  90  proceeds with the process to step S 31 . 
     In step S 31 , the controller  90  determines whether the number of times CX a leakage diagnosis of the fuel tank  26  is performed in the current stop period is less than the predetermined allowable number of times CA. Here, performing a leakage diagnosis is to execute the process from step S 41  (described later). At the beginning of the current stop period, that is, at the time when the internal combustion engine  10  stops, the number of times CX is zero. In step S 31 , when the controller  90  determines that the number of times CX in the current stop period is greater than or equal to the allowable number of times CA (NO in S 31 ), the controller  90  ends the current leakage diagnosis control. On the other hand, in step S 31 , when the controller  90  determines that the number of times CX in the current stop period is less than the allowable number of times CA (YES in S 31 ), the controller  90  proceeds with the process to step S 32 . 
     In step S 32 , the controller  90  determines whether the predetermined diagnosis condition is satisfied. For example, the case where the diagnosis condition is satisfied is a case where any one of the following Condition (C) and Condition (D) is satisfied. 
     Condition (C): The process of step S 41  (described later) is not executed in the current stop period, and the length of the current stop period is longer than or equal to a predetermined prescribed period. 
     Condition (D): An elapsed time from the last execution of the process of step S 41  (described later) to the time of the process of step S 32  in the current stop period is longer than or equal to a predetermined prescribed period. 
     Here, an example of the prescribed period is several tens of minutes to several hours. In step S 32 , when the controller  90  determines that the diagnosis condition is not satisfied (NO in S 32 ), the controller  90  proceeds with the process to step S 21  again. On the other hand, in step S 32 , when the controller  90  determines that the diagnosis condition is satisfied (YES in S 32 ), the controller  90  proceeds with the process to step S 41 . 
     In step S 41 , the controller  90  executes the emission process of emitting gas from the fuel tank  26 . Specifically, the controller  90  closes the purge valve  38  and opens the shut-off valve  36  and the outside air valve  37 . The controller  90  emits gas from the fuel tank  26  to the outside via the vapor passage  31 , the canister  32 , and the outside air passage  33  by using the pump module  39 . At this time, evaporated fuel contained in gas in the fuel tank  26  is adsorbed by the canister  32 , so emission of gas containing evaporated fuel to the outside is suppressed. After that, the controller  90  proceeds with the process to step S 51 . 
     In step S 51 , the controller  90  determines whether the tank internal pressure PT is higher than a predetermined determination value. Here, the determination value is determined as follows. Initially, when there is no abnormality in the fuel tank  26 , the emission process of step S 41  is executed, with the result that the tank internal pressure PT becomes lower than or equal to a set value. On the other hand, when there occurs an abnormality, such as a crack, in the fuel tank  26 , even when the emission process of step S 41  is executed, the tank internal pressure PT does not become lower than or equal to the set value because gas enters from outside the fuel tank  26 . Therefore, the set value is obtained by an experiment or the like. Then, the set value is determined as a determination value. In step S 51 , when the controller  90  determines that the tank internal pressure PT is higher than the determination value (YES in S 51 ), the controller  90  proceeds with the process to step S 61 . 
     In step S 61 , the controller  90  determines that the fuel tank  26  is abnormal. After that, the controller  90  proceeds with the process to step S 62 . In step S 62 , the controller  90  notifies the driver or the like via the display  89  that the fuel tank  26  is abnormal by outputting a control signal to the display  89 . After that, the controller  90  ends leakage diagnosis control. 
     On the other hand, in step S 51 , when the controller  90  determines that the tank internal pressure PT is lower than or equal to the determination value (NO in S 51 ), the controller  90  proceeds with the process to step S 71 . In step S 71 , the controller  90  determines that the fuel tank  26  is normal. After that, the controller  90  proceeds with the process to step S 72 . In step S 72 , the controller  90  counts up the number of times CX by one. After that, the controller  90  proceeds with the process to step S 21  again. In the present embodiment, the process of step S 51 , step S 71 , and step S 72  is an example of the diagnosis process of performing a leakage diagnosis. The tank internal pressure PT detected by the pressure sensor  83  is an example of an index value indicating the pressure in the fuel tank  26 . 
     Operation of Present Embodiment 
     In the vehicle  100 , when a leakage diagnosis is performed in a stop period of the internal combustion engine  10 , gas is emitted from the fuel tank  26  to the outside via the vapor passage  31 , the canister  32 , and the outside air passage  33 . At this time, evaporated fuel contained in gas in the fuel tank  26  is adsorbed by the canister  32 . Therefore, each time a leakage diagnosis is performed, the amount of evaporated fuel adsorbed by the canister  32  increases. 
     When fuel is fed to the fuel tank  26  in the stop period of the internal combustion engine  10 , preparation control is executed. In the preparation control, the purge valve  38  is closed, and the shut-off valve  36  and the outside air valve  37  are opened. Then, as a result of feeding fuel to the fuel tank  26  from the fill opening  26 B, gas in the fuel tank  26  is pushed out to the vapor passage  31 . When gas in the fuel tank  26  moves to the canister  32 , evaporated fuel contained in gas is adsorbed by the canister  32 . As a result, even when a leakage diagnosis is not performed in the stop period of the internal combustion engine  10 , the amount of evaporated fuel adsorbed by the canister  32  increases. 
     Advantageous Effects of Present Embodiment 
     (1) In the vehicle  100 , when fuel has been fed to the fuel tank  26  in a stop period of the internal combustion engine  10 , the subtraction process of reducing the allowable number of times CA is executed. In other words, when the amount of evaporated fuel adsorbed by the canister  32  increases as a result of feeding fuel to the fuel tank  26 , the subtraction process of reducing the allowable number of times CA is executed. Therefore, after fuel is fed to the fuel tank  26 , the number of times CX a leakage diagnosis is performed is further strictly limited. Thus, an excessively large amount of evaporated fuel adsorbed by the canister  32  is suppressed. As a result, this reduces a situation in which a leakage diagnosis is performed regardless of the fact that the amount of evaporated fuel that is able to be adsorbed by the canister  32  is small and, as a result, gas containing evaporated fuel is emitted to the outside. 
     (2) In the vehicle  100 , the amount of subtraction of the allowable number of times CA increases when a large amount of fuel has been fed to the fuel tank  26  as compared to when a small amount of fuel has been fed to the fuel tank  26 . In other words, as the amount of evaporated fuel pushed out from the fuel tank  26  increases due to the fact that the amount of fuel fed to the fuel tank  26  increases, the amount of subtraction of the allowable number of times CA increases. Therefore, it is possible to adjust the allowable number of times CA by further accurately reflecting the amount of evaporated fuel adsorbed by the canister  32 . 
     (3) In the vehicle  100 , even when fuel is actually not fed to the fuel tank  26 , the lid door  29  can be set to an open state due to, for example, erroneous operation of the driver or the like. In this case as well, the open state of the lid door  29  is detected based on the open-close position LS, so the purge valve  38  is closed, and the shut-off valve  36  and the outside air valve  37  are opened. At this time, if the tank internal pressure PT is higher than the atmospheric pressure PA, gas in the fuel tank  26  is pushed out to the vapor passage  31 . When gas in the fuel tank  26  moves to the canister  32 , evaporated fuel contained in gas is adsorbed by the canister  32 . As a result, even when a leakage diagnosis is not performed in the stop period of the internal combustion engine  10 , the amount of evaporated fuel adsorbed by the canister  32  increases. 
     In terms of this point, in the vehicle  100 , when the tank internal pressure PT is higher than the atmospheric pressure PA and the shut-off valve  36  is opened in a stop period of the internal combustion engine  10 , the subtraction process of reducing the allowable number of times CA is executed. In other words, when the amount of evaporated fuel adsorbed by the canister  32  increases as a result of high pressure in the fuel tank  26 , the subtraction process of reducing the allowable number of times CA is executed. Therefore, the number of times CX a leakage diagnosis is performed is further strictly limited. Thus, an excessively large amount of evaporated fuel adsorbed by the canister  32  is suppressed. As a result, this reduces a situation in which a leakage diagnosis is performed regardless of the fact that the amount of evaporated fuel that is able to be adsorbed by the canister  32  is small and, as a result, gas containing evaporated fuel is emitted to the outside. 
     (4) In the vehicle  100 , when there is a large difference between the tank internal pressure PT and the atmospheric pressure PA, the amount of subtraction of the allowable number of times CA increases as compared to when there is a small difference between the tank internal pressure PT and the atmospheric pressure PA. In other words, as the amount of evaporated fuel pushed out from the fuel tank  26  increases due to a large difference between the tank internal pressure PT and the atmospheric pressure PA, the amount of subtraction of the allowable number of times CA increases. Therefore, it is possible to adjust the allowable number of times CA by further accurately reflecting the amount of evaporated fuel adsorbed by the canister  32 . 
     (5) In the above vehicle  100 , the vehicle  100  can be driven by using the driving force of only the second motor generator  72 , so there are many opportunities to stop the internal combustion engine  10 . As the opportunity to stop the internal combustion engine  10  increases, an opportunity to perform a leakage diagnosis increases. In the vehicle  100 , fuel can be fed while the internal combustion engine  10  is stopped as described above. In this way, it is suitable to apply the controller  90  that performs the leakage diagnosis to the vehicle  100  in which there are many opportunities to perform a leakage diagnosis and there are many opportunities to feed fuel during a stop of the internal combustion engine  10 . 
     (6) The battery  75  of the vehicle  100  is chargeable from the external power supply  200 . In the vehicle  100 , the battery  75  generally has a large capacity, so one stop period of the internal combustion engine  10  tends to be long. As a result, the number of times CX a leakage diagnosis is performed in one stop period of the internal combustion engine  10  tends to increase. Therefore, it is suitable to apply the controller  90  that performs the leakage diagnosis to the vehicle  100 . 
     Modifications 
     The present embodiment may be modified as follows. The present embodiment and the following modifications may be implemented in combination with each other without any technical contradiction. 
     In leakage diagnosis control of the above embodiment, a manner of setting the initial value of the allowable number of times CA in step S 11  may be changed. As a specific example, the amount of evaporated fuel adsorbed by the canister  32  at the beginning of the current stop period varies depending on the drive status of the internal combustion engine  10  just before the current stop period. For this reason, the controller  90  may change a value to be set as the initial value of the allowable number of times CA depending on the drive status of the internal combustion engine  10  just before the current stop period. In this way, even when the allowable number of times CA is variable according to the drive status of the internal combustion engine  10 , but when the controller  90  calculates the allowable number of times CA by using a prestored map, an arithmetic expression, or the like, the allowable number of times CA is a predetermined value. 
     In leakage diagnosis control of the above embodiment, the subtraction condition in step S 21  may be changed. Specifically, two conditions, that is, Condition (A) and Condition (B), do not need to be adopted, and only one of Condition (A) and Condition (B) may be adopted. 
     In leakage diagnosis control of the above embodiment, a manner of the subtraction process in step S 22  may be changed. As a specific example, when the controller  90  determines in the process of the last step S 21  that Condition (A) is satisfied, the allowable number of times CA may be reduced by a predetermined fixed number of times regardless of the amount of fuel fed to the fuel tank  26  in the current stop period. When the controller  90  determines in the process of the last step S 21  that Condition (B) is satisfied, the allowable number of times CA may be reduced by a predetermined fixed number of times regardless of a difference between the tank internal pressure PT and the atmospheric pressure PA at the time of the process of step S 22 . 
     In leakage diagnosis control of the above embodiment, the index value indicating the pressure in the fuel tank  26  in step S 51  may be changed. As a specific example, the pump module  39  can include a pressure sensor. In this case, a pressure detected by the pressure sensor of the pump module  39  may be used as the index value indicating the pressure in the fuel tank  26 . 
     In the above embodiment, the vehicle  100  does not need to be a plug-in hybrid electric vehicle. For example, the battery  75  does not need to be chargeable from the external power supply  200  provided outside the vehicle  100 . In this case, the converter  78  and the inlet  79  may be omitted. For example, the vehicle  100  does not need to include the first motor generator  71  and the second motor generator  72 . In other words, as long as the vehicle  100  includes the internal combustion engine  10  and the leakage diagnostic device that performs a diagnosis of the fuel supply system  25  that supplies fuel to the internal combustion engine  10 , the technology can be applied.