Leak Diagnostic Device

Abstract

To provide a leakage diagnosis system enabling improvement of accuracy of a leakage diagnosis of a fuel tank.SOLUTION: A leakage diagnosis device makes a leakage diagnosis of a fuel tank mounted to a vehicle. The leakage diagnosis device includes: a calculation section that calculates a change amount of pressure in the fuel tank and a change amount of a temperature of fuel in the fuel tank while ignition is turned off; and a determination section that determines presence / absence of leakage in the fuel tank. When the change amount of the pressure is larger than a pressure determination value, the determination section determines that there is no leakage in the fuel tank. When the change amount of the pressure is equal to or smaller than the pressure determination value and the change amount of the temperature is larger than a temperature determination value, the determination section determines that there is leakage in the fuel tank.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a leak diagnosis device. [Background technology]

[0002] There is a leak diagnosis device that is installed in a vehicle and performs a leak diagnosis on the fuel tank based on the pressure inside the fuel tank. Specifically, if there is a large change in engine temperature and there is a corresponding large change in pressure inside the fuel tank, it is diagnosed as not having a leak. However, if there is a small change in pressure despite a large change in engine temperature, it is diagnosed as having a leak (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2013-137035 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if the engine and fuel tank are mounted separately on a vehicle, the effect of the engine temperature change on the pressure in the fuel tank is small. In such a case, the above method may erroneously determine that there is a leak even though there is no leak, even though there is a large change in engine temperature. This may reduce the accuracy of the leak diagnosis.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a leak diagnosis device that improves the accuracy of leak diagnosis for a fuel tank mounted on a vehicle. [Means for solving the problem]

[0006] The above object can be achieved by a leak diagnosis device that performs leak diagnosis on a fuel tank mounted on a vehicle, the leak diagnosis device comprising: a calculation unit that calculates, while the ignition is off, an amount of change in pressure inside the fuel tank and an amount of change in temperature of the fuel inside the fuel tank; and a determination unit that determines whether or not there is a leak in the fuel tank, wherein if the amount of change in pressure is greater than a pressure determination value, the determination unit determines that there is no leak in the fuel tank, and if the amount of change in pressure is equal to or less than the pressure determination value and the amount of change in temperature is greater than a temperature determination value, the determination unit determines that there is a leak in the fuel tank.

[0007] The calculation unit may calculate the difference between the maximum and minimum values ​​of the pressure while the ignition is off as the amount of change in the pressure, and calculate the difference between the maximum and minimum values ​​of the temperature while the ignition is off as the amount of change in the temperature, and the temperature judgment value may be set based on the difference between the temperature of the saturated vapor of the fuel corresponding to the maximum value of the pressure and the temperature of the saturated vapor of the fuel corresponding to the minimum value of the pressure.

[0008] When the amount of change in the pressure is equal to or less than the pressure determination value and the amount of change in the temperature is equal to or less than the temperature determination value, the determination unit may not determine whether or not there is a leak in the fuel tank, and the calculation unit may continue to calculate the amount of change in the pressure and the amount of change in the temperature.

[0009] The pressure sensor may further include an acquisition unit that acquires the pressure and the temperature.

[0010] The temperature control system may further include an acquisition unit that acquires the pressure and the outside air temperature, wherein the calculation unit estimates multiple change patterns of the temperature based on changes in the outside air temperature, identifies a change pattern among the multiple change patterns that has the smallest difference between the maximum temperature value and the minimum temperature value, and calculates the difference between the maximum temperature value and the minimum temperature value in the identified change pattern as the amount of change in the temperature. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a leak diagnosis device that improves the accuracy of leak diagnosis for a fuel tank. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle. [Figure 2] 4 is a flowchart illustrating a leak diagnosis control. [Figure 3] 1 is a map that defines the saturated vapor pressure curve of a fuel. [Figure 4] 4 is a timing chart illustrating a leak diagnosis control. [Figure 5] FIG. 10 is a schematic diagram of a modified vehicle. [Figure 6] 10 is a flowchart illustrating a modified example of leak diagnosis control. [Figure 7] 10 is a timing chart illustrating a method for selecting a minimum pattern. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Vehicle outline] FIG. 1 is a schematic diagram of a vehicle 1. In this embodiment, the vehicle 1 is mounted on a vehicle. The vehicle 1 includes an engine 10, a fuel tank 30, and an ECU (Electronic Control Unit) 60. The fuel tank 30 stores fuel for the engine 10. The fuel in the fuel tank 30 is supplied to a fuel injection valve 12 via a fuel supply path. A pressure sensor 50 detects the pressure in the fuel tank 30. A fuel temperature sensor 52 detects the temperature of the fuel in the fuel tank 30.

[0014] Power from engine 10 is transmitted to drive wheels 20. Engine 10 is provided with a fuel injection valve 12 that injects fuel into combustion chamber 11, and a spark plug 13 that ignites an air-fuel mixture that is a mixture of the injected fuel and intake air. An intake passage 14 and an exhaust passage 15 are connected to combustion chamber 11. A surge fuel tank 16 is provided in intake passage 14. A throttle valve 17 is provided upstream of surge fuel tank 16.

[0015] A canister 31 is provided to adsorb evaporated fuel generated in the fuel tank 30. The canister 31 and the fuel tank 30 are connected via a vapor passage 32. A shut-off valve 42 is provided in the vapor passage 32 to open and close the vapor passage 32. By opening the shut-off valve 42, the evaporated fuel in the fuel tank 30 is temporarily collected in the adsorbent of the canister 31.

[0016] The canister 31 and the surge fuel tank 16 are connected to each other via a purge passage 33. A purge valve 43 that opens and closes the purge passage 33 is provided in the purge passage 33. An outside air introduction passage 36 that introduces outside air into the canister 31 is connected to the canister 31. An air filter 37 is provided at the open end of the outside air introduction passage 36.

[0017] The outside air introduction passage 36 is provided with a selector valve 46 that opens and closes the outside air introduction passage 36. When the engine 10 is running, the selector valve 46 opens the outside air introduction passage 36.

[0018] When a predetermined condition is met, the purge valve 43 is opened while the engine 10 is running, with the switching valve 46 open and the stop valve 42 closed. This causes the evaporated fuel to desorb from the canister 31. The desorbed evaporated fuel is introduced into the surge fuel tank 16 via the purge passage 33 and combusted in the combustion chamber 11.

[0019] The ECU 60 is an electronic control unit that includes a calculation processing circuit that performs various calculation processes related to the driving control of the vehicle 1, and a memory that stores control programs and data. The ECU 60 is connected to various sensors that detect the operating state of the engine 10, a pressure sensor 50, a fuel temperature sensor 52, an ignition switch 55, and the like. The ECU 60 executes various controls of the vehicle 1 and the engine 10 based on signals from these sensors and switches. The ECU 60 is an example of a leak diagnosis device, which will be described in detail later. The ECU 60 functionally realizes a calculation unit, a determination unit, and an acquisition unit.

[0020] [Leak diagnosis control] FIG. 2 is a flowchart illustrating leak diagnosis control. The ECU 60 determines whether or not it has detected that the ignition is turned off (step S1). If the answer is No in step S1, this control ends. If the answer is Yes in step S1, the ECU 60 sets the next startup time of the ECU 60 (step S2) and stops (step S3). The startup time of the ECU 60 is, for example, the time when a certain time has elapsed from immediately before the ECU 60 was stopped. The certain time is, for example, one hour. When the current time reaches the startup time, the ECU 60 automatically starts (step S4).

[0021] Next, the ECU 60 acquires the pressure PTn in the fuel tank 30 and the temperature TFn of the fuel in the fuel tank 30 based on the detection value of the pressure sensor 50 and the detection value of the fuel temperature sensor 52 (step S5). While the ignition is off, the ECU 60 repeatedly starts and stops, acquiring the above pressure and temperature each time it starts, as will be described in detail later. Therefore, the subscript n indicates the number of times the ECU 60 is started while the ignition is off. For example, the pressure and temperature acquired upon the first start-up while the ignition is off are represented as pressure PT1 and temperature TF1, respectively. The pressure and temperature acquired upon the second start-up while the ignition is off are represented as pressure PT2 and temperature TF2, respectively. Therefore, the ECU 60 acquires the above pressure and temperature at predetermined time intervals. The pressure PTn is a gauge pressure based on atmospheric pressure. Step S5 is an example of processing executed by the acquisition unit.

[0022] Next, the ECU 60 determines whether or not the leak determination has been completed (step S6). If the determination in step S6 is Yes, this control ends.

[0023] If the answer is No in step S6, the ECU 60 calculates a pressure change amount ΔPTn (step S7). The pressure change amount ΔPTn is the difference between the maximum and minimum values ​​of the pressures PT1, PT2, ..., PTn acquired by the ECU 60. In other words, the pressure change amount ΔPTn is the maximum value of the pressure change amounts that can be calculated based on the acquired pressures. Step S7 is an example of processing executed by the calculation unit.

[0024] Next, the ECU 60 determines whether the absolute value of the pressure PTn is higher than the pressure determination value A1 (step S8). Here, the pressure sensor 50 has a predetermined tolerance. Furthermore, atmospheric pressure fluctuates depending on the weather. Therefore, the pressure determination value A1 is set to a gauge pressure that is considered to be approximately atmospheric pressure, taking into account the tolerance of the pressure sensor 50 and the amount of fluctuation in atmospheric pressure. Therefore, if the determination in step S8 is Yes, the pressure in the fuel tank 30 is considered to be significantly different from atmospheric pressure. In this case, the ECU 60 determines that there is no leak in the fuel tank 30 (step S9).

[0025] If the answer is No in step S8, the ECU 60 determines whether the absolute value of the pressure change amount ΔPTn is higher than the pressure determination value A2 (step S10). Therefore, if the answer is Yes in step S10, the amount of change in pressure inside the fuel tank 30 is considered to be larger than the amount of fluctuation in atmospheric pressure. In this case, the ECU 60 determines that there is no leak in the fuel tank 30 (step S9). Step S10 is an example of processing executed by the determination unit.

[0026] If the answer is No in step S10, the ECU 60 calculates a temperature change amount ΔTFn (step S11). The temperature change amount ΔTFn is the difference between the maximum and minimum values ​​of the temperatures TF1, TF2, ... TFn acquired by the ECU 60. In other words, the temperature change amount ΔTFn is the maximum value of the temperature change amounts that can be calculated based on the acquired temperatures. Step S11 is an example of processing executed by the calculation unit.

[0027] Next, the ECU 60 determines whether the absolute value of the temperature change amount ΔTFn is greater than the temperature determination value B (step S12). The temperature determination value B is determined based on the saturated vapor pressure of the fuel. FIG. 3 is a map that defines a saturated vapor pressure curve of the fuel. The ECU 60 sets the temperature determination value B by referring to the map of FIG. 3. Specifically, the ECU 60 refers to the map of FIG. 3 and calculates a saturated vapor temperature corresponding to the saturated vapor pressure when the maximum value among the pressures PT1, PT2, ... PTn is set as the saturated vapor pressure of the fuel. Next, the ECU 60 refers to the map of FIG. 3 and calculates a saturated vapor temperature corresponding to the saturated vapor pressure when the minimum value among the pressures PT1, PT2, ... PTn is set as the saturated vapor pressure of the fuel. The ECU 60 sets the difference between these two saturated vapor temperatures as the temperature determination value B.

[0028] If the answer is No in step S10 and Yes in step S12, the amount of change in pressure inside the fuel tank 30 is considered to be small, even though the amount of change in fuel temperature due to the influence of outside air temperature, for example, is large. In this case, the ECU 60 determines that there is a leak in the fuel tank 30 (step S13). In this way, a leak diagnosis is performed based on the amount of change in pressure inside the fuel tank 30 and the amount of change in temperature of the fuel inside the fuel tank 30. Therefore, the leak diagnosis is performed with higher accuracy than when a leak diagnosis is performed based on, for example, the temperature of the engine 10. Step S12 is an example of processing executed by the determination unit.

[0029] If the answer is No in step S12, the ECU 60 does not determine whether or not there is a leak, and executes the processing from step S2 onwards again. As a result, the ECU 60 acquires new pressure PTn and temperature TFn (step S5), and continues calculating the pressure change amount ΔPTn (step S7) and the temperature change amount ΔTFn (step S11). In this way, if the answer is No in step S12, the processing from step S2 onwards is repeatedly repeated. That is, the ECU 60 automatically starts up at regular time intervals and continues calculating the pressure change amount ΔPTn and the temperature change amount ΔTFn. This also enables accurate leak diagnosis.

[0030] Fig. 4 is a timing chart illustrating leak diagnosis control. Fig. 4 shows the transition of the temperature of the fuel in the fuel tank 30 and the pressure in the fuel tank 30. Fig. 4 shows a first case, a second case, and a third case.

[0031] The first case will be described. At time t0, the ignition is turned off. At time t1, the ECU 60 acquires the pressure PT1 and the temperature TF1 (step S5). The pressure PT1 is greater than the pressure determination value A1 (Yes in step S8). Therefore, it is determined that there is no leak (step S9).

[0032] The second case will be described. The pressure PT1 at time t1 is smaller than the pressure determination value A1 (No in step S8). The pressure change amount ΔPT1 is also calculated as zero. Therefore, the pressure change amount ΔPT1 is smaller than the pressure determination value A2 (No in step S10). The temperature change amount ΔTF1 is also calculated as zero. Therefore, the temperature change amount ΔTF1 is smaller than the temperature determination value B (No in step S12).

[0033] The pressure PT2 at time t2 is smaller than the pressure determination value A1 (No in step S8). The pressure change amount ΔPT2 is the difference between the pressure PT1 and the pressure P2. The pressure change amount ΔPT2 is smaller than the pressure determination value A2 (No in step S10). The temperature change amount ΔTF2 is the difference between the temperature TF1 and the temperature TF2. The temperature change amount ΔTF2 is smaller than the temperature determination value B (No in step S12). The above processing is also performed at time t3.

[0034] The absolute value of pressure PT4 at time t4 is smaller than pressure determination value A1 (No in step S8). The absolute value of pressure change amount ΔPT4 is larger than pressure determination value A2 (Yes in step S10). Therefore, it is determined that there is no leak (step S9).

[0035] The third case will now be described. The absolute values ​​of the pressures PT1, PT2, PT3, PT4, and PT5 are smaller than the pressure determination value A1 (No in step S8). The absolute values ​​of the pressure changes ΔPT1, ΔPT2, ΔPT3, ΔPT4, and ΔPT5 are also smaller than the pressure determination value A2 (No in step S10). The absolute values ​​of the temperature changes ΔTF1, ΔTF2, ΔTF3, and TF4 are also smaller than the temperature determination value B (No in step S12). However, the absolute value of the temperature change ΔTF5 is larger than the temperature determination value B (Yes in step S12). Therefore, it is determined that a leak exists (step S13). Because the pressure is almost unchanged while the fuel temperature is changing significantly, it is possible to accurately determine that a leak exists.

[0036] [Variations] Fig. 5 is a schematic diagram of a modified vehicle 1a. Fig. 5 corresponds to Fig. 1. Regarding the modified vehicle, a description of the same configuration and processing as those in the above-described embodiment will be omitted. The vehicle 1a does not have the above-described fuel temperature sensor 52. The vehicle 1a has an outside air temperature sensor 53 that detects the outside air temperature.

[0037] Fig. 6 is a flowchart illustrating a modified example of leak diagnosis control. Fig. 6 corresponds to Fig. 2. If the answer to step S1 is Yes, ECU 60a acquires outside air temperature TA0 based on the detection value of outside air temperature sensor 53, and estimates temperature TFm_0 based on outside air temperature TA0 (step S1a). Temperature TFm_0 is an initial value of the change pattern of the temperature of the fuel in fuel tank 30, as will be described in detail later. m is an integer equal to or greater than 2. m indicates the number of change patterns of the temperature of the fuel to be estimated.

[0038] After executing the process of step S4, the ECU 60a acquires the pressure PTn in the fuel tank 30 and the outside air temperature TAn based on the detection value of the pressure sensor 50 and the detection value of the outside air temperature sensor 53 (step S5a). Step S5a is an example of a process executed by the acquisition unit.

[0039] The ECU 60a estimates a temperature TFm_n based on the outside air temperature TAn (step S5b). The temperature TFm_n is an estimated value of the temperature of the fuel in the fuel tank 30. Specifically, the ECU 60a estimates m types of temperature change patterns. m is an integer equal to or greater than 2. The temperatures TF1_0, TF1_1, ..., TF1_n are a first pattern. The temperatures TF2_0, TF2_1, ..., TF2_n are a second pattern. The temperatures TFm_0, TFm_1, ..., TFm_n are an m-th pattern. The ECU 60a selects one pattern from the first pattern to the m-th pattern as a minimum pattern TFJn (step S5c). The minimum pattern TFJn is selected as follows: For each of the first pattern to the m-th pattern, a difference between the maximum temperature value and the minimum temperature value is calculated. Of the differences between the first pattern to the m-th pattern, the pattern with the smallest difference is selected as the smallest pattern TFJn. Steps S5b and S5c are an example of processing executed by the calculation unit, and will be described in detail later.

[0040] If the answer is No in step S10, the ECU 60a calculates a temperature change amount ΔTFJn (step S11a). The temperature change amount ΔTFJn is the difference between the maximum and minimum temperatures in the minimum pattern TFJn. Step S11a is an example of a process executed by the calculation unit.

[0041] Next, the ECU 60a determines whether the absolute value of the temperature change amount ΔTFJn is greater than the temperature determination value B (step S12a). Step S12a is an example of a process executed by the determination unit.

[0042] As described above, the amount of change in fuel temperature is estimated based on the amount of change in outside air temperature, which eliminates the need for a fuel temperature sensor and reduces manufacturing costs.

[0043] FIG. 7 is a timing chart illustrating a method for selecting the minimum pattern TFJn. FIG. 7 illustrates the case where m=6. At time t0, the ignition is turned off, and the ECU 60a estimates temperatures TF1_0, TF2_0, ..., TF6_0 based on the outside air temperature TA0 (step S1a). Of these temperatures, temperature TF1_0 is the lowest temperature, and temperature TF6_0 is the highest temperature. Temperatures TF1_0, TF2_0, and TF3_0 are lower than the outside air temperature TA0. Temperatures TF4_0, TF5_0, and TF6_0 are higher than the outside air temperature TA0. Temperatures TF1_0, TF2_0, and TF3_0 differ from one another by a predetermined temperature. Temperatures TF3_0, TF4_0, TF5_0, and TF6_0 also differ from one another by a predetermined temperature. If these temperatures differ by, for example, 2 degrees, the following relationship holds: TF1_0=TA0-6 TF2_0=TA0-4 TF3_0=TA0-2 TF4_0=TA0+2 TF5_0=TA0+4 TF6_0=TA0+6

[0044] At time t1, the ECU 60a acquires the outside air temperature TA1 (step S5a). Furthermore, the ECU 60a estimates temperatures TF1_1, TF2_1, ... TF6_1 based on the outside air temperature TA1 (step S5b). The method of estimating these temperatures will be described later. The ECU 60a selects, from the first to sixth patterns, a pattern that minimizes the difference between the maximum and minimum temperature values ​​as the minimum pattern TFJn (step S5c). Specifically, the ECU 60a calculates the difference between temperatures TF1_0 and TF1_1, the difference between temperatures TF2_0 and TF2_1, the difference between temperatures TF3_0 and TF3_1, the difference between temperatures TF4_0 and TF4_1, the difference between temperatures TF5_0 and TF5_1, and the difference between temperatures TF6_0 and TF6_1. The pattern that minimizes these differences is selected as the minimum pattern TFJn.

[0045] Similarly, at time t2, the ECU 60a estimates temperatures TF1_2, TF2_2, ... TF6_2 based on the outside air temperature TA2 (step S5b). The ECU 60a selects a minimum pattern TFJn from the first to sixth patterns (step S5c). Specifically, the difference between the maximum and minimum values ​​of temperatures TF1_0, TF1_1, and TF1_2 of the first pattern is calculated. Similarly, the difference between the maximum and minimum values ​​of temperatures TF2_0, TF2_1, and TF2_2 of the second pattern is calculated. The difference between the maximum and minimum values ​​of temperatures TF3_0, TF3_1, and TF3_2 of the third pattern is calculated. The difference between the maximum and minimum values ​​of temperatures TF4_0, TF4_1, and TF4_2 of the fourth pattern is calculated. The difference between the maximum and minimum values ​​of temperatures TF5_0, TF5_1, and TF5_2 of the fifth pattern is calculated. The differences between the maximum and minimum values ​​of the temperatures TF6_0, TF6_1, and TF6_2 of the sixth pattern are calculated. The pattern with the smallest difference is selected as the minimum pattern TFJn. The same applies to times t3, t4, and t5.

[0046] In this way, the minimum pattern TFJn, which has the smallest amount of change in the estimated temperature, is estimated as the fuel temperature change pattern. This prevents the estimated temperature change amount ΔTFJn from being excessively large compared to the actual amount of change in the fuel temperature. This is because if the estimated temperature change amount ΔTFJn is excessively large compared to the actual amount of change in the fuel temperature, a erroneous determination of "Yes" may be made in step S12a. In this way, leak diagnosis is performed with high accuracy.

[0047] Next, we will explain how to estimate the temperature TFm_n of the fuel in the fuel tank 30. The temperature TFm_n excluding the temperature TFm_0 is estimated by the following equation. TFm_n=TFm_(n-1)+Eaf+Evf...(1) Eaf indicates the amount of change in fuel temperature due to thermal energy received by the fuel from the outside air, and Evf indicates the amount of change in fuel temperature due to thermal energy received by the fuel from the vapor fuel in the fuel tank 30. Eaf=(TAn-TFm_(n-1))*Jtf / (Htf / 1000)*Sfuel / Jf / FUELVOL*Δt...(2) EVf=(TVm_(n-1)-TFm_(n-1))*Jfv / (Hfv / 1000)*Sfv / Jf / FUELVOL*Δt...(3)

[0048] Jtf indicates the thermal conductivity between the wall of the fuel tank 30 and the fuel. Jfv indicates the thermal conductivity between the fuel and the evaporated fuel. Htf indicates the thickness of the wall of the fuel tank 30 between the fuel and the outside air. Hfv is the thickness of the virtual boundary surface between the fuel liquid surface and the evaporated fuel. Sfuel indicates the contact area between the fuel tank 30 and the fuel. Sfv indicates the contact area between the fuel and the evaporated fuel. Jf indicates the specific heat of the fuel. FUELVOL indicates the volume of the fuel in the fuel tank 30. Δt is the time interval over which TFm_n is calculated. TVm_(n-1) is the previous value of TVm_n. TVm_n is an estimated value of the temperature of the evaporated fuel in the fuel tank 30. Jtf, Jfv, Jf, Htf, and Hfv are pre-stored in the ROM of ECU 60a. Sfuel, Sfv, and FUELVOL are calculated by the ECU 60 a based on the amount of fuel in the fuel tank 30 .

[0049] TVm_n is calculated using the following formula: TVm_n=TVm_(n―1)+Efv+Eav···(4) Efv indicates the amount of change in the temperature of the evaporated fuel due to the thermal energy that the evaporated fuel receives from the fuel, and Eav indicates the amount of change in the temperature of the evaporated fuel due to the thermal energy that the evaporated fuel receives from the outside air. Efv=(TFm_n-TVm_(n-1))*Jfv / (Hfv / 1000)*Sfv / Jv / (TNKVOL-FUELVOL)*Δt...(5) Eav=(TAn-TVm_(n-1))*Jtv / (Htv / 1000)*Svapor / Jv / (TNKVOL-FUELVOL)*Δt...(6)

[0050] Jv is the specific heat of the evaporated fuel. Htv indicates the thickness of the wall of the fuel tank 30 that exists between the evaporated fuel and the outside air. TNKVOL indicates the capacity of the fuel tank 30. Svapor indicates the contact area between the wall of the fuel tank 30 and the evaporated fuel. Jv and Htv are stored in advance in the ROM of the ECU 60a. TNKVOL and Svapor are calculated by the ECU 60a based on the amount of fuel in the fuel tank 30. As described above, the ECU 60a estimates the temperature TFm_n of the fuel in the fuel tank 30 based on the above equation.

[0051] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0052] 1 vehicle 30 Fuel Tank 50 Pressure Sensor 52 Fuel temperature sensor 53 Outside air temperature sensor 60, 60a ECU (leak diagnosis device, calculation unit, judgment unit, acquisition unit)

Claims

1. A leak diagnosis device for diagnosing leaks in a fuel tank mounted on a vehicle, a calculation unit that calculates a change amount of pressure in the fuel tank and a change amount of temperature of the fuel in the fuel tank while the ignition is off; a determination unit that determines whether or not there is a leak in the fuel tank, When the amount of change in the pressure is greater than a pressure determination value, the determination unit determines that there is no leak in the fuel tank, When the amount of change in the pressure is equal to or less than the pressure determination value and the amount of change in the temperature is greater than a temperature determination value, the determination unit determines that there is a leak in the fuel tank, the calculation unit calculates a difference between a maximum value and a minimum value of the pressure while the ignition is off as an amount of change in the pressure, and calculates a difference between a maximum value and a minimum value of the temperature while the ignition is off as an amount of change in the temperature, The temperature determination value is set based on a difference between a temperature of the saturated vapor of the fuel corresponding to the maximum value of the pressure and a temperature of the saturated vapor of the fuel corresponding to the minimum value of the pressure.

2. 2. The leak diagnosis device of claim 1, wherein, when the amount of change in the pressure is equal to or less than the pressure determination value and the amount of change in the temperature is equal to or less than the temperature determination value, the determination unit does not determine whether or not there is a leak in the fuel tank, and the calculation unit continues to calculate the amount of change in the pressure and the amount of change in the temperature.

3. The leak diagnosis device according to claim 1 , further comprising an acquisition unit that acquires the pressure and the temperature.

4. A leak diagnosis device for diagnosing leaks in a fuel tank mounted on a vehicle, a calculation unit that calculates a change amount of pressure in the fuel tank and a change amount of temperature of the fuel in the fuel tank while the ignition is off; a determination unit that determines whether or not there is a leak in the fuel tank, When the amount of change in the pressure is greater than a pressure determination value, the determination unit determines that there is no leak in the fuel tank, When the amount of change in the pressure is equal to or less than the pressure determination value and the amount of change in the temperature is greater than a temperature determination value, the determination unit determines that there is a leak in the fuel tank, an acquisition unit that acquires the pressure and the outside air temperature, The calculation unit estimates multiple temperature change patterns based on changes in outside air temperature, identifies one of the multiple change patterns in which the difference between the maximum temperature value and the minimum temperature value is smallest, and calculates the difference between the maximum temperature value and the minimum temperature value in the identified change pattern as the amount of change in temperature.

Images