Fuel vapor treatment system with failure diagnosis apparatus

A fuel vapor treatment system comprising:

• a fuel tank;
• a canister fluidly coupled to the fuel tank and configured to adsorb fuel vapor evaporated from the fuel tank;
• a purge valve disposed to open and close piping that fluidly couples the canister to an intake passage of an internal, combustion engine into which fuel vapor flows from the canister;
• a drain cut valve operatively coupled to the canister to open and close an atmospheric release port of the canister;
• an absolute pressure sensor configured and arranged to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on an open-closed statuses of the drain cut valve and the purge valve;
• a vehicle speed detecting device and a road slope estimating device;
• and
• a failure diagnosis control device configured and arranged to close off a portion of the fuel vapor treatment system between the fuel tank and the purge valve and conduct a leak diagnosis when a permission condition is met, the leak diagnosis control device being configured to conduct the failure diagnosis based on atmospheric pressure and a pressure change inside the portion of the fuel vapor treatment system while the portion of the fuel vapor treatment system is closed off, the failure diagnosis control device being further configured to cancel a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined, the failure diagnosis control device being further configured to determine that the predetermined condition for canceling the leak diagnosis result is satisfied when a change in atmospheric pressure exceeds a prescribed value with the change in atmospheric pressure being estimated based on a vehicle speed detected by the vehicle speed detecting device and a road slope estimated by the road slope estimating device.

A fuel vapor treatment system, comprising:

• a fuel tank;
• a canister fluidly coupled to the fuel tank and configured to adsorb fuel vapor evaporated from the fuel tank;
• a purge valve disposed to open and close piping that fluidly couples the canister to an intake passage of an internal combustion engine into which fuel vapor flows from the canister;
• a drain cut valve operatively coupled to the canister to open and close an atmospheric release port of the canister;
• an absolute pressure sensor configured and arranged to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on an open-closed statuses of the drain cut valve and the purge valve;
• and
• a failure diagnosis control device configured and arranged to close off a portion of the fuel vapor treatment system between the fuel tank and the purge valve and conduct a leak diagnosis when a permission condition is met, the failure diagnosis control device being configured to conduct the leak diagnosis based on atmospheric pressure and a pressure change inside the portion of the fuel vapor treatment system while the portion of the fuel vapor treatment system is closed off, the failure diagnosis control device being further configured to determine that a predetermined condition for canceling the leak diagnosis result is satisfied when a difference between the atmospheric pressure and the pressure inside the portion of the fuel vapor treatment system undergoing the leak diagnosis is greater than or equal to an opening pressure of a relief valve provided in a filler cap of the fuel tank.

A fuel vapor treatment system, comprising:

• a fuel tank;
• a canister fluidly coupled to the fuel tank and configured to adsorb fuel vapor evaporated from the fuel tank;
• a purge valve disposed to open and close piping that fluidly couples the canister to an intake passage of an internal combustion engine into which fuel vapor flows from the canister;
• a drain cut valve operatively coupled to the canister to open and close an atmospheric release port of the canister;
• an absolute pressure sensor configured and arranged to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on an open-closed statuses of the drain cut valve and the purge valve;
• and
• a failure diagnosis control device configured and arranged to close off a portion of the fuel vapor treatment system between the fuel tank and the purge valve and conduct a leak diagnosis when a permission condition is met, the failure diagnosis control device being configured to conduct the leak diagnosis based on atmospheric pressure and a pressure change inside the portion of the fuel vapor treatment system while the portion of the fuel vapor treatment system is closed off, the failure diagnosis control device being further configured to cancel a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined, the failure diagnosis control device being further configured to determine that the predetermined condition for canceling the leak diagnosis result is satisfied when a difference between the atmospheric pressure and the pressure inside the portion of the fuel vapor treatment system undergoing the leak diagnosis is greater than or equal to an opening pressure of a relief valve provided in a filler cap of the fuel tank.

A fuel vapor treatment system comprising:

• a fuel tank;
• a canister fluidly coupled to the fuel tank and configured to adsorb fuel vapor evaporated from the fuel tank;
• a purge valve disposed to open and close piping that fluidly couples the canister to an intake passage of an internal combustion engine into which fuel vapor flows from the canister;
• a drain cut valve operatively coupled to the canister to open and close an atmospheric release port of the canister;
• an absolute pressure sensor configured and arranged to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on an open-closed statuses of the drain cut valve and the purge valve;
• and
• a failure diagnosis control device configured and arranged to close off a portion of the fuel vapor treatment system between the fuel tank and the purge valve and conduct a leak diagnosis when a permission condition is met, the leak diagnosis control device being configured to conduct the failure diagnosis based on atmospheric pressure and a pressure change inside the portion of the fuel vapor treatment system while the portion of the fuel vapor treatment system is closed off the failure diagnosis control device being further configured to cancel a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined, the failure diagnosis control device being further configured to determine that the predetermined condition for canceling the leak diagnosis result is satisfied when a chance in atmospheric pressure exceeds a prescribed value, the failure diagnosis control device being further configured to determine that the predetermined condition for canceling the leak diagnosis result is satisfied when a difference between the atmospheric pressure and the pressure inside the portion of the fuel vapor treatment system undergoing the leak diagnosis is greater than or equal to an opening pressure of a relief valve provided in a filler cap of the fuel tank.

A fuel vapor treatment system comprising:

• storage means for containing fuel;
• canister means for adsorbing fuel vapor evaporated from the storage means;
• piping means for fluidly coupling the storage means to the canister means and an intake passage of an internal combustion engine;
• purge valve means for regulating fuel vapor flows from the canister means to the intake passage;
• drain cut valve means for controlling air flow into the canister;
• absolute pressure sensor means for detecting absolute pressure inside the fuel vapor treatment system and for measuring atmospheric pressure based on an open-closed statuses of the drain cut valve means and the purge valve means;
• and
• a failure diagnosis control means for closing off a portion of the fuel vapor treatment system between the storage means and the purge valve means, for conducting a leak diagnosis based on atmospheric pressure and a change in the absolute pressure inside the portion of the fuel vapor treatment system when the portion of the fuel vapor treatment system is closed off and a permission condition is met, for canceling a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined, for detecting a change in atmospheric pressure by comparing a first output value detected by the absolute pressure sensor before conducting the leak diagnosis and a second output value detected by the absolute pressure sensor after conducting the leak diagnosis, and for determining that the predetermined condition for canceling the leak diagnosis result is satisfied when the change in atmospheric pressure exceeds a prescribed value.

A method for diagnosing a fuel vapor treatment system, comprising:

• measuring absolute pressure inside the fuel vapor treatment system having a fuel tank fluidly connected to an intake passage of an internal combustion engine with a canister that is configured to adsorb fuel vapor evaporated from said fuel tank;
• determining an operational state of a drain cut valve operatively coupled to the canister of the fuel vapor treatment system;
• determining an operational state of a purge valve operatively coupled to the canister of the fuel vapor treatment system;
• using a single absolute pressure sensor to detect absolute pressure inside the fuel vapor treatment system and measure atmospheric pressure based on the operational states of the drain cut valve and the purge valve;
• conducting a failure diagnosis on the fuel vapor treatment system based on atmospheric pressure and a change in the absolute pressure inside the portion of the fuel vapor treatment system when the portion of the fuel vapor treatment system is closed off by the drain cut valve and the purge valve and a permission condition is met;
• canceling a leak diagnosis result obtained by the leak diagnosis when a predetermined condition for canceling the leak diagnosis result is determined;
• detecting a change in atmospheric pressure by comparing a first output value detected by the absolute pressure sensor before conducting the leak diagnosis and a second output value detected by the absolute pressure sensor after conducting the leak diagnosis;
• and
• determining that the predetermined condition for canceling the leak diagnosis result is satisfied when the change in atmospheric pressure exceeds a prescribed value.