JP4715426B2 - Leak diagnostic device for evaporative fuel processing system - Google Patents

Description

  The present invention relates to a leak diagnosis apparatus for an evaporated fuel processing system.

  In a vehicular engine, fuel evaporative gas (hereinafter referred to as “evaporative gas”) generated in a fuel tank is adsorbed on activated carbon in the canister, and the canister and the intake passage of the engine are connected under predetermined operating conditions. By opening the purge control valve provided in the communicating passage and using the negative pressure of the intake passage, the fuel particles adsorbed in the canister are desorbed from the activated carbon and led to the intake passage downstream of the throttle valve, An evaporative fuel processing system adapted to be combusted is provided.

  In this case, if there is a leak hole in the middle of the flow path from the fuel tank to the intake pipe or if the seal at the joint of the pipe becomes poor, the evaporative gas will be released into the atmosphere. Various leak diagnosis methods have been proposed.

  One of them is a leak diagnosis (hereinafter referred to as “evaporation diagnosis when stopped”) that is performed after the engine is stopped, not during engine operation. The stop-time evaporative diagnosis is performed based on the amount of change in the differential pressure by detecting the transition of the differential pressure between the pressure in the evaporated fuel processing system and the atmospheric pressure after the engine is stopped.

  This stop-evaporation diagnosis is based on a pressure change in the evaporated fuel processing system caused by a temperature change in the fuel tank due to natural heat dissipation after the engine is stopped. Therefore, when the temperature rise in the fuel tank is insufficient, such as when the engine is stopped immediately after being operated, the temperature change after the engine stops is small, and therefore the pressure change is also small. Becomes higher.

Therefore, in Patent Document 1, the value of the difference between the outside air temperature detected by the outside air temperature sensor and the air layer temperature detected by the air layer temperature sensor in the fuel tank is smaller than a predetermined value in the stop-time evaporation policy. In this case, an invention relating to a leak diagnosis apparatus for an evaporated fuel processing system that prohibits leak diagnosis in order to prevent erroneous determination is disclosed.
JP 2003-113743 A

  The above-described conventional leak diagnosis apparatus for an evaporative fuel processing system detects the air layer temperature in the fuel tank, and sets the difference between the air layer temperature and the outside air temperature as a prohibition condition for leak diagnosis. However, the pressure change in the fuel tank is largely caused by the pressure change caused by the change in the saturated vapor pressure of the fuel accompanying the change in the fuel temperature, and the pressure change due to the change in the gas layer temperature is small.

  For example, if the air temperature is higher than the outside air temperature, but the fuel temperature is not different from the outside air temperature, and the inside of the fuel tank does not reach the saturated vapor pressure, the fuel component continues to evaporate. In such a case, while the gas layer temperature decreases, the fuel component evaporates, so the pressure change decreases, and the conventional leak diagnosis method may cause a false diagnosis.

  The present invention has been made paying attention to such a conventional problem, and its purpose is to determine whether or not the amount of heat received by the fuel in the fuel tank from the outside during traveling is determined in the leak diagnosis in the stop-time evaporative diagnosis. It is an object of the present invention to provide a leak diagnosis apparatus for an evaporative fuel processing system that can perform a more accurate leak diagnosis under the conditions.

The leak diagnosis apparatus for an evaporated fuel processing system according to the present invention includes an engine stop state detecting means for detecting a stop state of the engine, a means for performing a leak diagnosis of the evaporated fuel processing system after the engine is stopped, and the fuel in the fuel tank is outside air temperature. The calculation means for calculating the amount of heat received by the fuel from the outside with reference to the amount of heat at the time of starting the cold machine, and the calculated amount of heat received when the engine is stopped are compared with a first predetermined value. Determination means for determining whether or not to permit the leak diagnosis, fuel temperature detection means for detecting the fuel temperature in the fuel tank, outside air temperature detection means for detecting the outside air temperature, and engine water temperature detection for detecting the engine water temperature And when the engine is cold-started, the calculation means calculates the amount of heat received based on the fuel temperature when the engine is started and the fuel temperature when the engine is stopped. And, when the engine starts warming up and calculates the heat quantity based on the fuel temperature and the ambient temperature when the engine is stopped.

According to the present invention, when the engine starts cold, the fuel temperature is calculated based on the fuel temperature when the engine is started and the fuel temperature when the engine is stopped. When the engine is warm-started, the fuel temperature and the outside air temperature when the engine is stopped are calculated. based on the received quantity of heat is calculated based on, since it is determined whether or not to allow leakage diagnosis, to prevent misdiagnosis, it is possible to perform an accurate leak diagnosis.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a leak diagnosis apparatus for a fuel vapor treatment system according to the present invention.

  In FIG. 1, 1 is an engine, 2 is an intake passage of the engine 1, and 3 is an exhaust passage. The intake passage 2 is provided with an intake air amount sensor 4 that detects the intake air amount and a throttle valve 5 that is located downstream of the intake passage 2 and controls the intake air amount. Furthermore, a fuel injection valve 6 that is located downstream of the throttle valve 5 and injects fuel is installed in the intake passage 2. Fuel is injected from the fuel injection valve 6 according to the amount of intake air, and the engine 1 generates an output by burning the fuel / air mixture in the engine 1.

  A fuel tank 10 stores fuel to be supplied to the engine 1 for temporarily adsorbing and holding the evaporated gas generated in the fuel tank 10 and for sucking and holding the absorbed and adsorbed evaporated gas into the engine 1 according to operating conditions. An evaporative fuel processing system 100 is provided.

  The evaporative fuel processing system 100 includes a canister 11 filled with activated carbon that adsorbs and holds an evaporative gas. The canister 11 is connected to the fuel tank 10 via an evaporation gas passage 12, and is also connected to the intake passage 2 downstream of the throttle valve 5 via a purge passage 13.

  The purge passage 13 is provided with a purge control valve 7 for adjusting the amount of evaporation gas purged into the intake passage 2 (hereinafter referred to as “purge amount”). The purge control valve 7 is normally closed and is configured so that the opening degree of the valve can be continuously controlled. The controller 30 described later performs opening / closing control corresponding to the purge amount.

  Further, the canister 11 is connected to the atmosphere via the atmosphere opening 9. A normally open drain cut valve 8 is provided at the atmosphere opening 9, and its operation is controlled by the controller 30. The drain cut valve 8 is closed at the time of leak diagnosis, which will be described later, and the inside of the evaporation system constituted by the fuel tank 10, the evaporation gas passage 12, the canister 11, and the purge passage 13 from the canister 11 to the purge control valve 7 is defined as a closed space. To do.

The purge passage 13 between the canister 11 and the purge control valve 7 is provided with a pressure sensor 14 that detects the pressure in the purge passage 13. This pressure sensor 14 outputs a signal to the controller 30 in accordance with the pressure in the evaporation system that is closed in the leak diagnosis.
A fuel pump 21 that pumps fuel is provided in the fuel tank 10 to supply the fuel to the fuel injection valve 6 through a fuel passage 22. A fuel temperature sensor 15 that detects the fuel temperature is provided in the fuel tank 10. The fuel temperature sensor 15 outputs a signal corresponding to the fuel temperature in the fuel tank 10 to the controller 30.

  The controller 30 further includes an intake air temperature sensor 17 that is incorporated in the intake air amount sensor 4 to detect the intake air temperature, an outside air temperature sensor 18 that detects the outside air temperature, each detection signal of the water temperature sensor 19 that detects the engine water temperature, and an ignition switch. A switching signal from 20 is input.

  The controller 30 includes a CPU, a ROM, a RAM (not shown), and the like. The purge control valve 7 is opened under predetermined operating conditions, and the fuel adsorbed to the canister 11 is sucked into the engine 1 through the intake passage 2 and burned. On the other hand, after stopping the engine, the purge control valve 7 and the drain cut valve 8 are controlled to be opened and closed, thereby performing a stop-time evaporative diagnosis for diagnosing the presence or absence of leakage in the evaporation system.

  Further, the controller 30 determines the amount of heat received by the fuel in the fuel tank 10 while the vehicle is running, and determines whether or not to permit the leak diagnosis based on the diagnosis of the stop-time evaporation. It has become.

  The stop-time evaporation diagnosis executed by the controller 30 will be described in detail with reference to the flowchart of FIG. This flow is repeatedly executed every predetermined single hour.

First, at the start of each trip (one run from when the engine is started to when the engine is turned off), the fuel temperature TFIN at the start of the trip (detected by the fuel temperature sensor 15) is stored as the initial fuel temperature ( Not shown).
Thereafter, when the trip is completed, the routine shown in FIG. 2 is started, and it is determined whether or not the ignition switch (IGNSW) 20 is turned on in step S101. If the ignition switch 20 is not turned on, the process proceeds to step S102 and subsequent steps in order to determine whether or not the stop-time evaporative diagnosis is performed. If the ignition switch 20 is on, this routine is terminated.

  Next, in step S102, the fuel temperature TFOF at the end of the trip (detected by the fuel temperature sensor 15) is stored.

  In step S103, from the engine water temperature at the time of start (detected by the water temperature sensor 19) and the intake air temperature (detected by the intake air temperature sensor 17), whether the trip before executing this routine was the cold start running (COLDSTART), It is determined whether the vehicle has started running after warming up. Specifically, when the difference between the starting water temperature and the intake air temperature is equal to or less than a predetermined value, it is determined that the vehicle starts traveling when cold, and when it is equal to or greater than the predetermined value, it is determined that traveling after warming is started.

  When a sufficient time has elapsed since the previous trip, that is, when the vehicle starts running when cold, the difference between the starting water temperature and the intake air temperature is small because the starting water temperature is approximately equal to the outside air temperature. On the other hand, when the time has not passed since the previous trip, that is, when the vehicle starts running after warming up, the starting water temperature is higher than the outside air temperature, and the difference between the starting water temperature and the intake air temperature is large. It is to become.

  If it is determined that the trip before the execution of the routine is the start of running when cold, the process proceeds to step S104. Similarly, if it is determined that running after warm-up is started, the process proceeds to step S106.

  In step S104, the amount of heat received by the fuel from the outside during traveling based on the outside air temperature (hereinafter referred to as “fuel heat receiving amount”) CDTF is calculated when it is determined that the vehicle is traveling cold.

  In general, the fuel in the fuel tank 10 receives an amount of heat from the outside due to heat radiation from an exhaust system or the like during traveling, and the temperature rises. In this embodiment, the amount of fuel heat received CDTF when it is determined that the vehicle starts traveling when cold is the temperature difference between the fuel temperature TFIN at the start of the trip and the fuel temperature TFOF at the end of the trip, that is, the fuel temperature change during the travel. Yes.

  This is because, in the case of the start of traveling when the vehicle is cold, the fuel temperature TFIN at the start of the trip can be estimated to be substantially the same as the outside air temperature, so that the temperature difference from the fuel temperature TFOF at the end of the trip can be used as the fuel heat receiving amount.

  In step S105, it is determined whether the fuel heat receiving amount CDTF calculated in step S104 is larger or smaller than a predetermined value DOK. If the fuel heat receiving amount CDTF is equal to or greater than the predetermined value DOK, it is assumed that a sufficient amount of heat is stored in the fuel in the fuel tank 10 for performing the stop-evaporation diagnosis, and the process proceeds to step S109. Diagnosis is performed.

  If the necessary and sufficient amount of heat is stored in the fuel in the fuel tank 10, the temperature change of the fuel temperature that drops due to heat exchange with the outside air after the engine is stopped is large, and therefore the pressure change is also large. This is because diagnosis can be prevented and diagnosis accuracy can be improved.

  Conversely, if the fuel heat received amount CDTF is less than or equal to the predetermined value DOK, it is prohibited to perform leak diagnosis on the assumption that a sufficient amount of heat is not stored in the fuel in the fuel tank when performing the evaporative diagnosis at the time of stopping. Is done.

  On the other hand, if it is determined in step S103 that the vehicle has started warming up as described above, the process proceeds to step S106. In step S106, the outside air temperature AMBTEMP detected by the outside air temperature sensor 18 is stored.

  Thereafter, the fuel heat receiving amount HDTF when it is determined in step S107 that the vehicle has started warming up is calculated. In the present embodiment, the fuel heat receiving amount HDTF when it is determined that the vehicle has started running after warm-up is the temperature difference between the fuel temperature TFOF at the end of the trip and the outside air temperature AMBTEMP.

  When the vehicle starts running after warming up, the fuel temperature at the start of the trip may already be higher than the outside air temperature. In this case, since the fuel already has heat, the temperature difference between the fuel temperature TFIN at the start of the trip and the fuel temperature TFOF at the end of the trip cannot be the amount of heat received by the fuel. This is because if the fuel temperature that rises due to the amount of heat received from the outside during traveling rises to a certain temperature, it balances the balance between heat reception and heat dissipation and does not rise any further. Therefore, if the temperature difference between the fuel temperature TFIN at the start of the trip and the fuel temperature TFOF at the end of the trip is defined as the amount of received heat, the diagnosis may be prohibited because the amount of received heat is small, and the diagnosis frequency can be secured. Because it disappears.

  Therefore, in the case of running after warm-up, the temperature difference between the fuel temperature TFOF at the end of the trip and the outside air temperature AMBTEMP is used as the fuel heat receiving amount.

  In step S108, it is determined whether the fuel heat receiving amount HDTF calculated in step S107 is larger or smaller than a predetermined value DDOK.

  If the fuel heat receiving amount HDTF is equal to or greater than the predetermined value DDOK, it is determined that the necessary and sufficient amount of heat is stored in the fuel in the fuel tank when performing the stop-time evaporation diagnosis. Is implemented.

  On the other hand, if the fuel heat received amount CDTF is less than or equal to the predetermined value DDOK, it is prohibited to perform leak diagnosis on the assumption that a sufficient amount of heat is not stored in the fuel in the fuel tank when performing the evaporative diagnosis at the time of stopping. Is done.

  As described above, the means for detecting the amount of received fuel differs depending on whether the vehicle starts traveling when the vehicle is cold or after the vehicle is warmed up. This is because, in the case of cold start, the fuel temperature TFIN at the start of the trip can be estimated to be substantially the same as the outside air temperature, so that the temperature difference from the fuel temperature TFOF at the end of the trip can be used as the fuel heat receiving amount. However, when the vehicle starts running after warming up, the fuel temperature at the start of the trip may already be higher than the outside air temperature. In this case, since the fuel already has a heat amount, the correlation between the temperature difference between the fuel temperature TFIN at the start of the trip and the fuel temperature TFOF at the end of the trip and the amount of heat received by the fuel during traveling is weakened.

  According to the leak diagnosis apparatus for an evaporative fuel processing system of the present embodiment described above, the fuel heat reception amount during traveling, which is a direct factor of the pressure change in the fuel tank, is set as a permit condition for leak diagnosis. Accordingly, when the leak diagnosis is permitted, a sufficient pressure change accompanying the fuel temperature change can be obtained, so that an accurate leak diagnosis can be performed.

  In the case of cold start, the difference between the fuel temperature at the start of the trip and the fuel temperature at the end of the trip is used as the fuel heat reception amount, so the difference between the outside air temperature and the fuel temperature at the end of the trip is the fuel heat reception amount. Compared to the case where the fuel temperature is changed, a more accurate fuel temperature change can be estimated, and when a misdiagnosis is likely to occur, the leak diagnosis can be accurately prohibited.

  Further, during execution of the stop-time evaporative diagnosis, it is necessary to energize in order to close the normally open drain cut valve 8, which increases the burden on the battery. Therefore, by prohibiting leak diagnosis when misdiagnosis is likely to occur, wasteful consumption of the battery can be prevented.

  The present invention is not limited to the above embodiment, and can be implemented in various modes without departing from the scope of the invention.

  For example, in step S103 of FIG. 2, the determination as to whether or not the vehicle has started running when cold is determined from the difference between the starting water temperature and the intake air temperature, but this may be determined from the difference between the starting water temperature and the outside air temperature. . Further, the outside air temperature stored in step S106 may be detected by the intake air temperature sensor 17.

  In addition, after storing the fuel temperature TFOF at the end of the trip without determining whether to start traveling when the engine is cold or after warming up, the temperature difference between the fuel temperature TFOF and the outside temperature AMBTEMP at the end of the trip is determined as the amount of received heat. In addition, it may be determined whether or not to perform the evaparak diagnosis when the vehicle stops based on the amount of the heat received by the fuel. That is, in FIG. 2, after step S102, step S103 is not performed, the process proceeds to step S106, and the processes of steps S107, S108, and S109 are performed.

  Since the amount of fuel heat received is determined based on the outside air temperature, if the temperature difference between the fuel temperature TFOF at the end of the trip and the outside air temperature AMBTEMP is defined as the amount of fuel heat received during traveling, This is because it is possible to determine whether or not a necessary and sufficient amount of heat has been stored in order to carry out the leak diagnosis without determining whether or not to start running.

  INDUSTRIAL APPLICABILITY The present invention can be used in an apparatus that is mounted on a vehicle and processes fuel evaporative gas generated by evaporating fuel in a fuel tank.

It is a figure which shows the structure of the leak diagnostic apparatus of the evaporative fuel processing system by this invention. It is a flowchart at the time of performing the evaporative diagnosis at the time of a stop.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Evaporative fuel processing system 1 Engine 2 Intake passage 10 Fuel tank 11 Canister 15 Fuel temperature sensor (fuel temperature detection means)
17 Intake air temperature sensor (intake air temperature detection means)
18 Outside air temperature sensor (outside air temperature detecting means)
19 Water temperature sensor (Engine water temperature detection means)
20 Ignition switch (Engine stop state detection means)
30 controller

Claims (3)

In an evaporative fuel processing system for purging evaporative fuel in a fuel tank to an intake passage,
Engine stop state detecting means for detecting the engine stop state;
Means for performing a leak diagnosis of the evaporated fuel processing system after the engine is stopped;
Calculation means for calculating the amount of heat received from the outside of the fuel tank when the temperature of the fuel in the fuel tank is at the outside temperature or when starting the cold machine,
A determination means for comparing the calculated amount of heat received when the engine is stopped with a first predetermined value to determine whether to permit the leak diagnosis;
Fuel temperature detecting means for detecting the fuel temperature in the fuel tank;
An outside air temperature detecting means for detecting the outside air temperature;
An engine water temperature detecting means for detecting the engine water temperature,
The computing means is
When the engine starts cold, the amount of heat received is calculated based on the fuel temperature when the engine is started and the fuel temperature when the engine is stopped.
A leak diagnosis apparatus for an evaporative fuel processing system, wherein when the engine is warmed up, the amount of heat received is calculated based on a fuel temperature and an outside air temperature when the engine is stopped . The computing means is
When the difference between the engine water temperature at engine start and the outside air temperature is less than the second predetermined value, the amount of heat received is calculated based on the fuel temperature at engine start and the fuel temperature at engine stop,
The amount of heat received is calculated based on the fuel temperature and the outside air temperature when the engine is stopped when the difference between the engine water temperature at the time of starting the engine and the outside air temperature is a second predetermined value or more. Diagnostic device for evaporative fuel treatment system. The determination means includes
When heat amount of the first predetermined value or more to allow the leakage diagnosis, the evaporated fuel of claim 1 or 2 heat amount when less than a first predetermined value and inhibits the leakage diagnosis Leak diagnostic device for processing system.

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