Leak diagnosis device for fuel vapor treatment equipment

Abstract

To provide a leak diagnosis device for an evaporation fuel treatment device that secures valve opening performance of a changeover valve.SOLUTION: A leak diagnosis device for an evaporation fuel treatment device includes: a first diagnosis section that makes leak diagnosis of a fuel tank on the basis of a tank internal pressure while a seal valve is closed; a determination section that determines whether valve opening performance of a changeover valve is affected by opening a seal valve while a purge valve and the changeover valve are closed when the tank internal pressure is within a normal range; and a second diagnosis section that makes leak diagnosis of a canister on the basis of the tank internal pressure or a canister internal pressure when the determination section makes negative determination and that makes the leak diagnosis of the canister on the basis of the canister internal pressure after closing the seal valve when the determination section makes affirmative determination.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a leak diagnosis device for an evaporated fuel treatment device. [Background technology]

[0002] A leak diagnosis device is known that performs a leak diagnosis between the fuel tank and canister of an evaporated fuel treatment device. The leak diagnosis is performed as follows. First, a leak diagnosis of the fuel tank is performed based on the internal tank pressure with the shut-off valve closed. If the internal tank pressure is within the normal range, it is determined that there is no leak abnormality in the fuel tank. Next, with the purge valve and the switching valve closed, the shut-off valve is opened and a leak diagnosis of the canister is performed based on the internal tank pressure (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2012-149592 Summary of the Invention [Problem to be solved by the invention]

[0004] Even when there is no leak in the fuel tank, the internal tank pressure may be high. In such a state, a canister leak diagnosis may be performed. If the shut-off valve is opened while the purge valve and switching valve are closed during the canister leak diagnosis, the pressure from the fuel tank may act on the switching valve, which may affect the opening ability of the switching valve.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a leak diagnosis device for an evaporated fuel treatment device that ensures the opening of a switching valve. [Means for solving the problem]

[0006] The object is to provide a leak diagnosis device for an evaporated fuel treatment device including a fuel tank for storing fuel for an internal combustion 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 an intake passage of the internal combustion engine and the canister, a closing valve for opening and closing the vapor passage, a purge valve for opening and closing the purge passage, an outside air introduction passage for introducing outside air into the canister, a switching valve for opening and closing the outside air introduction passage, a first detection unit for detecting tank internal pressure which is the pressure inside the fuel tank, and a second detection unit for detecting canister internal pressure which is the pressure inside the canister. This can be achieved by a leak diagnosis device for an evaporated fuel treatment device, which includes a first diagnosis unit that performs a leak diagnosis of the fuel tank based on the tank internal pressure when the shut-off valve is in a closed state; a judgment unit that, when the tank internal pressure is within a normal range, opens the shut-off valve with the purge valve and the switching valve closed and judges whether or not this affects the opening ability of the switching valve; and a second diagnosis unit that, if the judgment unit makes a negative judgment, performs a leak diagnosis of the canister based on the tank internal pressure or the canister internal pressure, and, if the judgment unit makes a positive judgment, closes the shut-off valve and then performs a leak diagnosis of the canister based on the canister internal pressure.

[0007] The determination unit determines that the opening ability of the switching valve is affected when the internal pressure of the canister becomes equal to or greater than a threshold value after the blocking valve is opened while the purge valve and the switching valve are closed, and the threshold value may be a pressure value that is higher than standard atmospheric pressure and lower than the internal pressure of the canister at which the opening ability of the switching valve is affected.

[0008] The second diagnosis unit may open the switching valve after diagnosing the canister for a leak.

[0009] The switching valve may be an electromagnetic valve including a valve body, a solenoid that applies a thrust to the valve body, and a return spring that applies a force to the valve body in a direction opposite to the thrust of the solenoid, and when the solenoid is energized, the thrust of the solenoid becomes greater than the force of the return spring, causing the valve body to close the outside air introduction passage, and when the solenoid is deenergized, the thrust of the solenoid becomes smaller than the force of the return spring, causing the valve body to open the outside air introduction passage. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a leak diagnosis device for an evaporated fuel treatment device that ensures the opening property of a switching valve. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram of an evaporated fuel treatment device applied to an engine. [Figure 2] 2A and 2B are schematic diagrams of a switching valve. [Figure 3] FIG. 3 is a flowchart illustrating the leak diagnosis control executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Outline of the fuel vapor treatment device] FIG. 1 is a schematic diagram of an evaporated fuel processing device 3 applied to an engine 1. In this embodiment, the engine 1 and evaporated fuel processing device 3 are mounted on a vehicle. The engine 1 is provided with a fuel injection valve 12 that injects fuel into a 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 the combustion chamber 11. A surge tank 16 that forms part of the intake passage 14 is provided midway in the intake passage 14. A throttle valve 17 that adjusts the amount of intake air is provided upstream of the intake of the surge tank 16.

[0013] The evaporated fuel processing device 3 includes a fuel tank 30 that stores fuel. The fuel in the fuel tank 30 is supplied to the fuel injection valve 12 via a fuel supply path. The fuel tank 30 is provided with a tank internal pressure sensor 50 that detects the tank internal pressure, which is the pressure inside the fuel tank 30. The evaporated fuel processing device 3 prevents evaporated fuel generated in the fuel tank 30 from being released into the atmosphere.

[0014] The evaporated fuel treatment device 3 is provided with a canister 31 that adsorbs evaporated fuel generated in a fuel tank 30. The canister 31 and the fuel tank 30 are connected via a vapor passage 32. A shut-off valve 42 that opens and closes the vapor passage 32 is provided in the vapor passage 32. By opening the shut-off valve 42, the evaporated fuel in the fuel tank 30 is temporarily collected in an adsorbent provided in the canister 31.

[0015] The canister 31 and the surge tank 16 are connected by a purge passage 33. A purge valve 43 that opens and closes the purge passage 33 is provided midway through 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.

[0016] A switching valve 46 that opens and closes the outside air introduction passage 36 is provided in the outside air introduction passage 36. The switching valve 46, which will be described in detail later, is a solenoid valve that opens the outside air introduction passage 36 when de-energized and closes the outside air introduction passage 36 when energized. In addition, a canister internal pressure sensor 51 that can detect the canister internal pressure, which is the pressure on the canister 31 side, is provided between the canister 31 and the switching valve 46. The switching valve 46 and the canister internal pressure sensor 51 will be described in detail later. During engine operation, the switching valve 46 is maintained so as to open the outside air introduction passage 36, that is, so that outside air can be introduced into the canister 31.

[0017] The engine 1 and the evaporative fuel treatment device 3 are controlled by an ECU (Electronic Control Unit) 60. The ECU 60 is an electronic control unit including a processing circuit that performs various arithmetic operations related to vehicle driving control 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 1, a tank pressure sensor 50, a canister pressure sensor 51, an ignition switch 55 operated by the vehicle driver, and the like. The ECU 60 executes various controls of the evaporative fuel treatment device 3 and the engine 1 based on signals from these sensors and switches. The ECU 60, which will be described in detail later, is an example of a leak diagnosis device for an evaporative fuel treatment device, and functionally realizes a determination unit, a first diagnosis unit, and a second diagnosis unit.

[0018] When a predetermined condition is met, the ECU 60 performs a purge process during engine operation by opening the purge valve 43 while the switching valve 46 is open and the stop valve 42 is closed. This causes evaporated fuel to be desorbed from the canister 31, and the desorbed evaporated fuel is introduced into the surge tank 16 via the purge passage 33 and combusted in the combustion chamber 11.

[0019] [Outline of canister pressure sensor] 2A and 2B are schematic diagrams of the switching valve 46. FIG. 2A shows the switching valve 46 in an open state. FIG. 2B shows the switching valve 46 in a closed state. As will be described in detail below, the switching valve 46 is open when de-energized and closed when energized. The switching valve 46 includes a valve element 461, a solenoid 463, and a return spring 465. The solenoid 463 applies a thrust to the valve element 461. The return spring 465 applies a biasing force to the valve element 461 in the direction opposite to the thrust of the solenoid 463. When the solenoid 463 is de-energized, the biasing force of the return spring 465 positions the valve element 461 at a position that opens the throttle section 36a, as shown in FIG. 2A. In other words, the return spring 465 biases the valve element 461 in the valve-opening direction. When solenoid 463 is energized, the thrust of solenoid 463 becomes greater than the biasing force of return spring 465. As a result, the thrust of solenoid 463 moves valve element 461 in the valve closing direction against the biasing force of return spring 465. As a result, valve element 461 closes throttle portion 36a as shown in FIG. 2B.

[0020] One end of a sensor passage 361 is inserted into the outside air introduction passage 36. The other end of the sensor passage 361 is connected to a canister pressure sensor 51. When the switching valve 46 is in a non-energized state, the valve element 461 closes one end of the sensor passage 361 due to the biasing force of a return spring 465. When the switching valve 46 is in an energized state, the valve element 461 moves away from the one end of the sensor passage 361. An opening 361a is formed in the sensor passage 361, and the canister pressure sensor 51 can detect the pressure inside the outside air introduction passage 36.

[0021] The ECU 60 executes leak diagnosis control for the evaporated fuel treatment device 3. During the execution of the leak diagnosis control, as shown in FIG. 2B , the canister pressure may become high while the switching valve 46 is closed. When the canister pressure becomes high, the force acting on the valve element 461 in the direction opposite to the biasing direction of the return spring 465 may become greater than the biasing force of the return spring 465. This may cause the valve element 461 to remain closed, and even if the solenoid 463 is de-energized, the valve may not open immediately or may not be able to open at all. This problem could be solved by, for example, using a return spring 465 with a large biasing force. However, this may increase the size of the switching valve 46. Therefore, in this embodiment, the ECU 60 executes the following leak diagnosis control.

[0022] [Leak diagnosis control] FIG. 3 is a flowchart illustrating the leak diagnosis control executed by the ECU 60. This control is continuously repeated while the ignition is on. The ECU 60 determines whether or not a precondition for leak diagnosis is met (step S1). This precondition is a condition for determining whether the generation of fuel vapor in the fuel tank 30 is stable. For example, the following condition is met.

[0023] The first condition is when the ignition is turned on after the internal combustion engine has been stopped for a long period of time (longer than a preset reference time) due to parking, etc., and the period is from when the ignition switch is turned on to just before the purge valve 43 is opened and the intake passage 14 is first purged. The second condition is when several hours (e.g., 5 hours) have passed since the ignition was turned off, and the coolant temperature detected by the coolant temperature sensor is equal to or lower than a predetermined temperature (e.g., 35°C). Note that the intake air temperature detected by the intake air temperature sensor may be used instead of the coolant temperature. Such first condition or second condition is set as a precondition. Note that the precondition may also be a logical OR condition of the first condition and the second condition. If the answer to step S1 is No, this control is terminated.

[0024] If the answer is Yes in step S1, a first leak diagnosis is performed as follows. The ECU 60 determines whether the tank internal pressure is within a normal range based on the detection value of the tank internal pressure sensor 50 (step S2). "Within the normal range" means a range that excludes a pressure range that can be considered to be approximately atmospheric pressure, taking into account the tolerance of the tank internal pressure sensor 50. In other words, if the tank internal pressure is a high or negative pressure that excludes the range that can be considered to be approximately atmospheric pressure, it can be assumed that no leak has occurred in the fuel tank 30. This is because if a leak has occurred in the fuel tank 30, the tank internal pressure will be approximately atmospheric pressure.

[0025] If the answer is No in step S2, the ECU 60 counts up counter A (step S3). Next, the ECU 60 determines whether counter A is greater than a predetermined value (step S4). If the answer is No in step S4, the ECU 60 suspends the leak diagnosis (step S5). If the answer is Yes in step S4, the ECU 60 determines that there is a leak abnormality in the fuel tank 30 (step S6). In this manner, the first leak diagnosis is performed. Steps S2 to S4 and S6 are an example of processing executed by the first diagnosis unit.

[0026] If the answer to step S2 is Yes, the tank internal pressure is considered to be within the normal range, and the ECU 60 performs a second leak diagnosis as follows: The ECU 60 closes the switching valve 46 (step S7), and then opens the stop valve 42 (step S8). As a result, the tank internal pressure is transmitted to the inside of the canister 31, the portion of the outside air introduction passage 36 between the canister 31 and the switching valve 46, the valve body 461 of the switching valve 46, and the portion of the purge passage 33 between the canister 31 and the purge valve 43.

[0027] Next, the ECU 60 determines whether or not the opening ability of the switching valve 46 is affected (step S9). Specifically, the ECU 60 determines that the opening ability of the switching valve 46 is affected when the canister pressure rises to or above a threshold based on the detection value of the canister pressure sensor 51. The threshold is a pressure value that is higher than the standard atmospheric pressure and lower than the canister pressure that affects the opening ability of the switching valve 46. The canister pressure that affects the opening ability of the switching valve 46 is determined in advance based on experimental results and simulation results. Step S9 is an example of processing executed by the determination unit.

[0028] If the answer is Yes in step S9, the ECU 60 closes the shutoff valve 42 (step S10), thereby preventing the canister internal pressure from becoming higher and ensuring that the switching valve 46 can be opened.

[0029] If the answer is No in step S9 or after step S10 has been executed, the ECU 60 determines whether the canister internal pressure is within the normal range based on the detection value of the canister internal pressure sensor 51 (step S11). If the answer is No in step S11, the ECU 60 counts up counter B (step S12). Next, the ECU 60 determines whether counter B is greater than a predetermined value (step S13). If the answer is No in step S13, the ECU 60 reserves the leak diagnosis result (step S5). If the answer is Yes in step S13, the ECU 60 determines that there is a leak abnormality in the canister 31 (step S14).

[0030] If the answer is Yes in step S11, the ECU 60 determines that the fuel tank 30 and the canister 31 are normal in terms of leaks (step S15), and resets counters A and B (step S16). After executing step S14 or S16, the ECU 60 opens the switching valve 46 (step S17). By opening the switching valve 46, if a purge request is made, the purge valve 43 can be immediately opened to perform the purge process. Steps S11 to S17 are an example of the process executed by the second diagnosis unit.

[0031] In this manner, it is possible to perform a leak check on the fuel tank 30 and the canister 31 while ensuring the opening property of the switching valve 46. Furthermore, it is possible to perform a purge process after the leak check.

[0032] If the answer to step S9 is No, the ECU 60 may determine whether the canister pressure is within the normal range based on the detection value of the tank pressure sensor 50. If the answer to step S9 is No, the purge valve 43 and the switching valve 46 are closed and the stop valve 42 is open, so the tank pressure and the canister pressure indicate the same value.

[0033] 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]

[0034] 1 engine 3. Fuel vapor treatment device 30 Fuel Tank 31 canister 32 Vapor passage 33 Purge Passage 36 Fresh air intake passage 37 Air Filter 42 Shut-off valve 43 Purge valve 46 Switching valve 50 Tank pressure sensor 51 Canister pressure sensor 60 ECU (leak diagnosis device, judgment unit, first diagnosis unit, second diagnosis unit)

Claims

1. a fuel tank for storing fuel for the internal combustion engine; a canister for absorbing evaporated fuel generated in the fuel tank; a vapor passage communicating the fuel tank and the canister; a purge passage that connects an intake passage of the internal combustion engine and the canister; a shutoff valve that opens and closes the vapor passage; a purge valve that opens and closes the purge passage; an outside air introduction passage for introducing outside air into the canister; a switching valve that opens and closes the outside air introduction passage; a first detection unit that detects a tank internal pressure, which is a pressure inside the fuel tank; a second detection unit that detects a canister internal pressure, which is the pressure inside the canister; A leak diagnosis device for an evaporated fuel treatment device, comprising: a first diagnosing unit that performs a leak diagnosis on the fuel tank based on the tank internal pressure when the shut-off valve is closed; a determination unit that, when the tank internal pressure is within a normal range, opens the blocking valve with the purge valve and the switching valve closed, and determines whether or not the opening property of the switching valve is affected; a second diagnosis unit that, when the determination unit makes a negative determination, executes a leak diagnosis of the canister based on the canister internal pressure, and, when the determination unit makes a positive determination, closes the block valve and then performs a leak diagnosis of the canister based on the canister internal pressure, the determination unit determines that the opening property of the switching valve is affected when the canister internal pressure becomes equal to or greater than a threshold value after the blocking valve is opened with the purge valve and the switching valve closed, the threshold value is a pressure value that is higher than standard atmospheric pressure and lower than the canister internal pressure that affects the opening property of the switching valve, When the tank internal pressure is not within a normal range in the leak diagnosis of the fuel tank, the first diagnosis unit determines that there is a leak abnormality in the fuel tank, and the determination unit does not determine whether there is an effect on the opening property of the switching valve, and the second diagnosis unit does not perform a leak diagnosis of the canister, The second diagnostic unit determines that the fuel tank and canister have normal leaks when the canister internal pressure is within a normal range, and determines that the canister has an abnormal leak when the canister internal pressure is not within the normal range.

2. 2. The leak diagnosis device for an evaporated fuel treatment device according to claim 1, wherein the second diagnosis unit opens the switching valve after diagnosing the canister for a leak.

3. the switching valve is an electromagnetic valve including a valve body, a solenoid that applies a thrust to the valve body, and a return spring that applies a biasing force to the valve body in a direction opposite to the thrust of the solenoid, When the solenoid is energized, the thrust of the solenoid becomes greater than the biasing force of the return spring, causing the valve body to close the outside air introduction passage.

3. The leak diagnosis device for an evaporated fuel treatment device according to claim 1, wherein when the solenoid is de-energized, the thrust of the solenoid becomes smaller than the biasing force of the return spring, thereby causing the valve body to open the outside air introduction passage.

Images