Engine system diagnostic device

Abstract

To provide a diagnostic device for an engine system, which has improved accuracy in diagnosing leaks in a fuel tank.SOLUTION: A diagnostic device has a shut-off valve that opens and closes a vapor passage, a purge valve, a canister internal pressure sensor, a tank internal pressure sensor, and a pressure reducing pump that reduces a canister internal pressure, and includes a tank main body that stores fuel and is provided with the tank internal pressure sensor, a fuel introduction pipe, and a check valve. The diagnostic device comprises: a determination unit that determines whether or not a tank internal pressure is equal to or higher than atmospheric pressure in the state that the engine is stopped and a closing command is issued to the shut-off valve; a canister leak diagnostic unit that performs a leak diagnosis on the canister when the determination unit makes a positive determination; and a tank leak diagnostic unit that, when it is determined that there is no leak in the canister, performs a leak diagnosis on the fuel tank on the basis of at least one of the canister internal pressure and the tank internal pressure after operation of the pressure reducing pump is started with a closing command issued to the purge valve and an opening command issued to the shut-off valve.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a diagnostic device for an engine system. [Background Art]

[0002] When the internal pressure of a fuel tank provided in an engine system is equal to or higher than atmospheric pressure, it may be diagnosed that there is no leak in the fuel tank (see, for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

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

[0004] A fuel tank includes a tank main body that stores fuel, and a fuel introduction pipe communicating with the tank main body. Here, it is conceivable to provide a check valve that allows introduction of fuel from the fuel introduction pipe into the tank main body but restricts reverse flow of fuel from the tank main body into the fuel introduction pipe. In this case, when the internal pressure of the tank main body is equal to or higher than atmospheric pressure, the check valve may be maintained in a state of closing the fuel introduction pipe. In this case, even if there is a leak in the fuel introduction pipe, when the internal pressure of the tank main body is equal to or higher than atmospheric pressure, there is a risk of misdiagnosis that there is no leak in the fuel tank.

[0005] In view of the above, an object of the present invention is to provide a diagnostic device for an engine system that improves the accuracy of leak diagnosis for a fuel tank. [Means for Solving the Problem]

[0006] The above objective is a diagnostic device for an engine system comprising: an engine; a fuel tank storing fuel for the engine; a canister for adsorbing evaporated fuel generated in the fuel tank; a vapor passage connecting the fuel tank and the canister; a purge passage connecting the intake passage of the engine and the canister; a sealing valve for opening and closing the vapor passage; a purge valve for opening and closing the purge passage; a canister pressure sensor for detecting the canister pressure, which is the internal pressure of the canister; a tank pressure sensor for detecting the tank pressure, which is the internal pressure of the fuel tank; and a pressure reducing pump for reducing the canister pressure to below atmospheric pressure, wherein the fuel tank comprises: a tank body for storing fuel and equipped with the tank pressure sensor; a fuel introduction pipe communicating with the tank body; and This can be achieved by an engine system diagnostic device comprising: a check valve that allows fuel to be introduced from the fuel introduction pipe to the tank body but restricts the backflow of fuel from the tank body to the fuel introduction pipe; a determination unit that determines whether the internal pressure of the tank is greater than or equal to atmospheric pressure when the engine is stopped and a closing command has been issued to the sealing valve; a canister leak diagnosis unit that performs a leak diagnosis of the canister when the determination unit makes a positive determination; and a tank leak diagnosis unit that, when it is determined that there is no leak in the canister, performs a leak diagnosis of the fuel tank based on at least one of the internal pressure of the canister and the internal pressure of the tank after the operation of the pressure reducing pump has started with a closing command issued to the purge valve and an opening command issued to the sealing valve.

[0007] The engine system includes a relief passage that bypasses the sealing valve and is connected to the vapor passage, and a positive pressure relief valve that opens the relief passage when the tank pressure is higher than the canister pressure and the pressure difference between the tank pressure and the canister pressure is greater than or equal to a predetermined opening pressure. The system also includes an open-lock diagnosis unit that performs an open-lock diagnosis when the determination unit makes an affirmative determination, and the operation of the pressure reducing pump is started with a valve closing command issued to the purge valve and the sealing valve, thereby reducing the canister pressure from atmospheric pressure by a predetermined amount, and the amount of reduction in the tank pressure is greater than or equal to a determination value, and the system also includes a setting unit that sets the determination value as a first value if the pre-start pressure, which is the tank pressure before the start of operation of the pressure reducing pump, is less than a threshold obtained by subtracting the amount of reduction from the opening pressure, and sets the determination value as a second value which increases as the pre-start pressure increases if the pre-start pressure is greater than or equal to the threshold.

[0008] The canister leak diagnostic unit performs a leak diagnosis of the canister based on the internal pressure of the canister after the pressure reducing pump starts operating with a valve closing command issued to the purge valve and the sealing valve, and the open-lock diagnostic unit may perform the open-lock diagnosis while the canister leak diagnosis is being performed.

[0009] The second value may be the value obtained by subtracting the threshold from the pre-start pressure and adding the first value. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an engine system diagnostic device that improves the accuracy of fuel tank leak diagnosis. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram of the engine system. [Figure 2] This is a magnified view of the area around the sealing valve. [Figure 3] This is a flowchart illustrating diagnostic control. [Figure 4]This is a flowchart illustrating the diagnosis of open fixation. [Figure 5] This map illustrates the relationship between the initial pressure P and the judgment value J. [Modes for carrying out the invention]

[0012] [Overall configuration of the engine system] Figure 1 is a schematic diagram of the engine system 1. In this embodiment, the engine system 1 is mounted on a vehicle. The engine system 1 comprises 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 the fuel injector 12 via a fuel supply path. The tank pressure sensor 50 detects the pressure inside the fuel tank 30.

[0013] The power of the engine 10 is transmitted to the drive wheels 20. The engine 10 is equipped with a fuel injector 12 that injects fuel into the combustion chamber 11, and a spark plug 13 that ignites the fuel-air mixture, which is a mixture of the injected fuel and intake air. An intake passage 14 and an exhaust passage 15 are connected to the combustion chamber 11. A surge fuel tank 16 is provided in the intake passage 14. A throttle valve 17 is provided upstream of the surge fuel tank 16.

[0014] The fuel tank 30 includes a tank body 30a, a fuel introduction pipe 30b, and a check valve 30c. The tank body 30a stores fuel. The fuel introduction pipe 30b guides fuel to the tank body 30a. The check valve 30c allows fuel to be introduced from the fuel introduction pipe 30b to the tank body 30a, but restricts the backflow of fuel from the tank body 30a to the fuel introduction pipe 30b. This prevents fuel from leaking to the outside from the tank body 30a through the fuel introduction pipe 30b. The check valve 30c is, for example, a cantilevered on / off valve, but it may also be a ball check valve.

[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 by a vapor passage 32. The vapor passage 32 is provided with a sealing valve 42 that opens and closes the vapor passage 32. By opening the sealing valve 42, evaporated fuel in the fuel tank 30 is temporarily collected by the adsorbent material of the canister 31.

[0016] Figure 2 is an enlarged view of the area around the sealing valve 42. Relief passages 32a and 32b, which bypass the sealing valve 42, are connected to the vapor passage 32. A positive pressure relief valve 44a and a negative pressure relief valve 44b are provided in the relief passages 32a and 32b, respectively. When the tank internal pressure is higher than the canister internal pressure and the pressure difference between the tank internal pressure and the canister internal pressure is greater than or equal to a predetermined opening pressure, the positive pressure relief valve 44a opens the relief passage 32a. When the tank internal pressure is lower than the canister internal pressure and the pressure difference between the tank internal pressure and the canister internal pressure is greater than or equal to a predetermined opening pressure, the negative pressure relief valve 44b opens the relief passage 32b. This prevents the tank internal pressure from becoming excessively high or excessively low.

[0017] The canister 31 and the surge fuel tank 16 are connected by a purge passage 33. The purge passage 33 is provided with a purge valve 43 for opening and closing the purge passage 33. The canister 31 is connected to an outside air intake passage 36 for introducing outside air into the canister 31. An air filter 37 is provided at the open end of the outside air intake passage 36.

[0018] A module 46 is provided in the outside air intake passage 36. Module 46 includes a canister internal pressure sensor 46a, a pressure reducing pump 46b, and a switching valve 46c. The canister internal pressure sensor 46a detects the canister internal pressure, which is the internal pressure of the canister 31. The pressure reducing pump 46b reduces the canister internal pressure to below atmospheric pressure. The switching valve 46c opens and closes the outside air intake passage 36. While the engine 10 is running, the switching valve 46c opens the outside air intake passage 36. The pressure reducing pump 46b can reduce the canister internal pressure regardless of the open or closed state of the switching valve 46c.

[0019] When a predetermined condition is satisfied, the purge valve 43 is opened while the switching valve 46c is opened and the blocking valve 42 is closed during operation of the engine 10. This desorbs evaporated fuel from the canister 31. The desorbed evaporated fuel is introduced into the surge fuel tank 16 via the purge passage 33, and is combusted in the combustion chamber 11.

[0020] The ECU 60 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to vehicle travel control, and a memory that stores control programs and data. Various sensors that detect the operating state of the engine 10, a canister internal pressure sensor 46a, a tank internal pressure sensor 50, an ignition switch 55, and the like are connected to the ECU 60. The ECU 60 executes various controls for the vehicle and the engine 10 based on signals from these sensors and switches. The ECU 60 issues a valve opening command or a valve closing command to each of the blocking valve 42, the purge valve 43, and the switching valve 46c. As will be described in detail later, the ECU 60 is an example of a diagnostic device for the engine system 1. The ECU 60 functionally implements a determination unit, a canister leak diagnosis unit, a tank leak diagnosis unit, an open sticking diagnosis unit, and a setting unit.

[0021] [Diagnostic Control] FIG. 3 is a flowchart illustrating diagnostic control. The ECU 60 determines whether or not ignition off has been detected (step S1). If No in step S1, the present control ends. If Yes in step S1, the ECU 60 sets the next startup time of the ECU 60 (step S2). Thereafter, the ECU 60 stops (step S3). Note that the startup time of the ECU 60 is, for example, a time after a fixed period has elapsed from immediately before the ECU 60 stops. The fixed period is, for example, one hour. When the current time reaches the startup time, the ECU 60 automatically starts up (step S4).

[0022] Next, the ECU 60 determines whether the tank pressure is equal to or greater than atmospheric pressure (step S5). Atmospheric pressure fluctuates depending on weather and altitude. Therefore, atmospheric pressure here does not mean 0 kPa in gauge pressure, but rather takes into account a predetermined range of fluctuation, for example, -0.2 kPa to +0.2 kPa. Thus, for example, if the tank pressure is -0.2 kPa or higher, it is determined that the tank pressure is equal to or greater than atmospheric pressure. Step S5 is an example of the process performed by the determination unit. If the answer in step S5 is No, this control ends.

[0023] [Canister leak diagnosis] If the answer in step S5 is Yes, the ECU 60 performs a canister leak diagnosis (step S6). In the canister leak diagnosis, the ECU 60 diagnoses whether there is a leak in the canister 31 based on the canister internal pressure after issuing a valve-closing command to the sealing valve 42 and the purge valve 43 and starting operation of the pressure reducing pump 46b. If the canister internal pressure is maintained at atmospheric pressure, the ECU 60 diagnoses that there is a leak in the canister 31. If the canister internal pressure becomes a negative pressure lower than atmospheric pressure, the ECU 60 diagnoses that there is no leak in the canister 31. Step S6 is an example of the process performed by the canister leak diagnosis unit.

[0024] Next, the ECU 60 determines whether or not a canister leak diagnosis is being performed (step S7). If the answer in step S7 is Yes, the ECU 60 performs an open-lock diagnosis (step S8). In other words, the open-lock diagnosis is performed while the canister leak diagnosis is being performed. The open-lock diagnosis is performed based on the tank pressure since the start of operation of the pressure reducing pump 46b in the canister leak diagnosis described above, and diagnoses whether the sealing valve 42 is stuck in the open position. Thus, the open-lock diagnosis is performed while the canister leak diagnosis is being performed. For this reason, both diagnoses are performed in a short amount of time. More details on the open-lock diagnosis will be described later.

[0025] Next, the ECU60 determines whether or not there is a leak in the canister 31 based on the diagnosis result of the canister leak diagnosis (step S9). If the result in step S9 is No, that is, if it is diagnosed that there is a leak in the canister 31, this control is terminated. Note that if the result in step S7 is No, step S9 is executed.

[0026] [Tank leak diagnosis] If the answer in step S9 is Yes, the ECU 60 performs a tank leak diagnosis (step S10). The tank leak diagnosis is performed as follows: The ECU 60 instructs the purge valve 43 to open, returning the canister pressure, which was reduced in the canister leak diagnosis, to atmospheric pressure. Next, the ECU 60 instructs the purge valve 43 to close and the sealing valve 42 to open, connecting the canister 31 and the fuel tank 30. Next, the ECU 60 starts operating the pressure reducing pump 46b. This reduces the pressure inside the canister 31 and the fuel tank 30. After starting the operation of the pressure reducing pump 46b, the ECU 60 performs a leak diagnosis of the fuel tank 30 based on at least one of the canister pressure and the tank pressure. If the amount of decrease in at least one of the canister pressure and the tank pressure from the start of operation of the pressure reducing pump 46b is greater than or equal to a determination value, it is diagnosed that there is no leak in the fuel tank 30. If, even after starting operation of the pressure reducing pump 46b, the decrease in at least one of the canister internal pressure and tank internal pressure is below a certain threshold, a leak in the fuel tank 30 is diagnosed. Step S10 is an example of the process performed by the tank leak diagnostic unit.

[0027] In this manner, when the tank internal pressure is greater than or equal to atmospheric pressure, a closing command is issued to the purge valve 43 and an opening command is issued to the sealing valve 42, and the tank leak diagnosis is performed. Therefore, even when the tank internal pressure is positive and the check valve 30c is closed on the fuel inlet pipe 30b, reducing the pressure inside the tank body 30a causes the check valve 30c to open the fuel inlet pipe 30b. This allows the leak diagnosis of the fuel tank 30, including the fuel inlet pipe 30b, to be performed. In this way, the accuracy of the fuel tank 30 leak diagnosis is improved.

[0028] [Diagnosis of open fixation] Next, we will explain the open-lock diagnosis. The open-lock diagnosis is performed based on the amount of pressure drop C in the tank when the depressurizing pump 46b is started in the canister leak diagnosis described above and the canister pressure is reduced from atmospheric pressure by a predetermined amount B. If the amount of pressure drop C in the tank is greater than or equal to the judgment value J, the sealing valve 42 is diagnosed as being open-locked. If the amount of pressure drop C in the tank is less than the judgment value J, the sealing valve 42 is diagnosed as not being open-locked.

[0029] As shown in Figure 2, a positive pressure relief valve 44a is provided in the relief passage 32a that bypasses the sealing valve 42. When the tank internal pressure is higher than the canister internal pressure and the pressure difference between the tank internal pressure and the canister internal pressure becomes equal to or greater than a predetermined opening pressure A, the positive pressure relief valve 44a opens. If the sealing valve 42 is not stuck open but closed, the canister internal pressure decreases when the pressure reducing pump 46b starts operating, and the pressure difference between the canister internal pressure and the tank internal pressure increases. When the pressure difference becomes equal to or greater than the opening pressure A, the positive pressure relief valve 44a opens and the tank internal pressure decreases. If the amount of decrease in tank internal pressure C at this time is equal to or greater than the judgment value J, there is a risk of misdiagnosis that the sealing valve 42 is stuck open even though it is closed. Therefore, the ECU 60 sets the judgment value J as follows.

[0030] Figure 4 is an example flowchart illustrating the diagnosis of open-locked valves. The ECU 60 determines whether the pre-start pressure P is less than the threshold T (step S11). The pre-start pressure P is the tank pressure before the operation of the pressure reducing pump 46b is started. The tank pressure used in the determination in step S5 may also be used as the pre-start pressure P. If the result in step S11 is Yes, the ECU 60 sets the determination value J to the first value D1 (step S12). If the result in step S11 is No, the ECU 60 sets the determination value J to the second value D2 (step S13). Next, it determines whether the decrease amount C is greater than or equal to the determination value J (step S14). If the result in step S14 is Yes, the ECU 60 diagnoses that the sealing valve 42 is open-locked (step S15). If the result in step S14 is No, the ECU 60 diagnoses that the sealing valve 42 is not open-locked (step S16).

[0031] Figure 5 is a map illustrating the relationship between the pre-start pressure P and the judgment value J. If the pre-start pressure P is less than the threshold T, the positive pressure relief valve 44a will not open even if the canister internal pressure is reduced by the depressurizing pump 46b. If the pre-start pressure P is equal to or greater than the threshold T, the positive pressure relief valve 44a will open due to the reduction in canister internal pressure by the depressurizing pump 46b. The threshold T is set to the value obtained by subtracting the reduction amount B from the opening pressure A. For example, if the opening pressure A is 20 kPa and the reduction amount B is 5 kPa, the threshold T is 15 kPa. If the pre-start pressure P is less than 15 kPa, the positive pressure relief valve 44a will not open even if the depressurizing pump 46b is activated. This is because even if the canister internal pressure drops by 5 kPa from atmospheric pressure, the difference between the canister internal pressure and the tank internal pressure is less than 20 kPa. If the pre-start pressure P is 15 kPa or higher, the positive pressure relief valve 44a opens due to the operation of the pressure reducing pump 46b. This is because when the canister internal pressure drops by 5 kPa from atmospheric pressure, the differential pressure becomes 20 kPa or more during the decrease in canister internal pressure.

[0032] Furthermore, if the canister internal pressure drops to -5kPa after the positive pressure relief valve 44a opens due to the operation of the pressure reducing pump 46b, the positive pressure relief valve 44a will close when the tank internal pressure falls below 15kPa. For example, if the initial pressure P was 17kPa, the positive pressure relief valve 44a will open when the canister internal pressure drops to -3kPa, and then close when the canister internal pressure drops to -5kPa and then falls below 15kPa. If the initial pressure P was 19kPa, the positive pressure relief valve 44a will open when the canister internal pressure drops to -1kPa, and then close when the canister internal pressure drops to -5kPa and then falls below 15kPa. Thus, the internal tank pressure when the positive pressure relief valve 44a closes is constant, regardless of the initial pressure P. In other words, the higher the initial pressure P, the greater the decrease C in internal tank pressure caused by the opening of the positive pressure relief valve 44a.

[0033] As shown in Figure 5, the first value D1 is a constant value regardless of the tank pressure. This is because if the pre-start pressure P is less than the threshold T, the positive pressure relief valve 44a will not open even when the pressure reducing pump 46b is activated. The second value D2 is a value greater than or equal to the first value D1, and it increases as the tank pressure increases. As mentioned above, if the pre-start pressure P is greater than or equal to the threshold T, the amount of pressure reduction C due to the opening of the positive pressure relief valve 44a increases as the pre-start pressure P increases. Therefore, in order to avoid the amount of pressure reduction C due to the opening of the positive pressure relief valve 44a exceeding the judgment value J, the second value D2 increases as the pre-start pressure P increases.

[0034] Furthermore, the first value D1 is smaller than the pressure reduction amount B. This is because if the sealing valve 42 is slightly open and stuck, the tank pressure may decrease with a delay compared to the reduction in canister pressure. For example, the first value D1 is 4 kPa. Also, if the pre-start pressure P is greater than or equal to the threshold T, the pre-start pressure P and the decrease C due to the opening of the positive pressure relief valve 44a are directly proportional. For this reason, the second value D2 may be the value obtained by adding the value obtained by subtracting the threshold T from the pre-start pressure P to the first value D1.

[0035] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0036] 1. Engine System 30 Fuel Tank 30a Tank body 30b Fuel Inlet Pipe 30c check valve 32 Vapor Passage 32a Relief aisle 42. Sealing valve 43. Purge valve 44a Positive pressure relief valve 46a Canister internal pressure sensor 46b Pressure Reducing Pump 46c Switching valve 50 Tank internal pressure sensor 60 ECU (Diagnostic device, judgment unit, canister leak diagnostic unit, tank leak diagnostic unit, open / stuck diagnostic unit, setting unit)

Claims

1. A diagnostic device for an engine system comprising: an engine; a fuel tank storing fuel for the engine; a canister for adsorbing evaporated fuel generated in the fuel tank; a vapor passage connecting the fuel tank and the canister; a purge passage connecting the intake passage of the engine and the canister; a sealing valve for opening and closing the vapor passage; a purge valve for opening and closing the purge passage; a canister pressure sensor for detecting the canister pressure, which is the internal pressure of the canister; a tank pressure sensor for detecting the tank pressure, which is the internal pressure of the fuel tank; and a pressure reducing pump for reducing the canister pressure to below atmospheric pressure, wherein The fuel tank includes a tank body that stores fuel and is equipped with a tank pressure sensor, a fuel introduction pipe communicating with the tank body, and a check valve that allows fuel to be introduced from the fuel introduction pipe to the tank body but restricts the backflow of fuel from the tank body to the fuel introduction pipe. A determination unit that determines whether the internal pressure of the tank is equal to or greater than atmospheric pressure when the engine is stopped and a valve closing command is issued to the sealing valve, A canister leak diagnosis unit performs a leak diagnosis of the canister when the determination unit makes a positive determination, A diagnostic device for an engine system, comprising: a tank leak diagnostic unit that, when it is determined that there is no leak in the canister, performs a fuel tank leak diagnosis based on at least one of the internal pressure of the canister and the internal pressure of the tank after the operation of the pressure reducing pump has started with a closing command issued to the purge valve and an opening command issued to the sealing valve.

2. The engine system includes a relief passage that bypasses the sealing valve and is connected to the vapor passage, and a positive pressure relief valve that opens the relief passage when the tank pressure is higher than the canister pressure and the pressure difference between the tank pressure and the canister pressure is greater than or equal to a predetermined opening pressure. If the determination unit makes a positive determination, and the depressurizing pump is started while a valve closing command is issued to the purge valve and the sealing valve, and the canister internal pressure is reduced by a predetermined amount from atmospheric pressure, the depressurizing unit performs an open-lock diagnosis if the amount of reduction in the tank internal pressure is greater than or equal to the determination value, and the sealing valve is deemed to be stuck open. A diagnostic device for an engine system according to claim 1, comprising: a setting unit that sets the determination value to a first value when the pre-start pressure, which is the internal pressure of the tank before the start of operation of the pressure reducing pump, is less than a threshold obtained by subtracting the amount of pressure reduction from the valve opening pressure; and a setting unit that sets the determination value to a second value which increases as the pre-start pressure increases when the pre-start pressure is equal to or greater than the threshold.

3. The canister leak diagnostic unit performs a leak diagnosis of the canister based on the internal pressure of the canister after the operation of the pressure reducing pump has started while a valve closing command has been issued to the purge valve and the sealing valve. The engine system diagnostic device according to claim 2, wherein the open-lock diagnosis unit performs the open-lock diagnosis while performing the leak diagnosis of the canister.

4. The diagnostic device for an engine system according to claim 2 or 3, wherein the second value is the value obtained by adding the first value to the value obtained by subtracting the threshold from the pre-start pressure.

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