Abstract: A fuel vapor purge system is configured to execute a highly accurate leak diagnosis with respect to a fuel vapor leak. After the engine is stopped, the temperature of the fuel vapor rises temporarily and then decreases until it reaches the outside ambient temperature. During this period, the purge line is closed off and a minimum value reached by the purge line pressure is detected. The difference between the minimum value of the purge line pressure and the atmospheric pressure is compared to a threshold value. The purge system is diagnosed as “normal” if the difference is equal to or larger than the threshold value and a “leaking” if the difference is less than the threshold value.

Abstract: Disclosed is a leak detecting device for a fuel vapor treatment unit that purges a vapor gas generated through evaporation of fuel in a fuel tank (2) into an intake system (22) of an engine (21). The leak detecting device includes a valve (5) that can selectively seal the fuel vapor treatment unit; a pressure detecting sensor (8) that detects a pressure in the fuel vapor treatment unit; and a controller (10). The controller (10) is programmed to: issue a command to close the valve (5) with a view to sealing the fuel vapor treatment unit during stoppage of the engine (21); calculate deviation amounts (P-P0) of the detected pressures during stoppage of the engine (21) after the fuel vapor treatment unit has been sealed; integrate absolute values (|P-P0|) of the deviation amounts, and determine, based on an integrated value (s), whether or not there is a leak occurring in the fuel vapor treatment unit.

Abstract: Fuel vapor in a fuel tank (1) is purged into an intake passage (8) of an engine (10) through a purge vent (2, 4, 6). The controller (21) determines whether a leak is present in a purge vent from the fuel tank (1) to a purge control valve (11). The determination process comprises a pull-down process in which a pressure in the purge vent is reduced using a negative pressure in the intake passage (8) and a leak-down process of sealing the purge vent at the reduced pressure and monitoring the pressure variation. The controller (21) calculates an error equivalence amount (DVPII), a pressure component corresponding to sloshing in the fuel tank (1) during the leak-down process, and determines the presence of a leak in a highly accurate manner based a corrected pressure (DVP5A) in which the monitored pressure variation is corrected using the error equivalence amount (DVPII) (S22).

Abstract: A failure diagnosis apparatus for an exhaust gas recirculation system eliminates the influence of various disturbance factors that vary the suction air pressure, diagnoses a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and prevents incorrect diagnosis. The system includes a fresh air pressure unit for determining an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine and an actual exhaust gas recirculation pressure estimating unit for determining an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting unit and estimated fresh air pressure. A failure is judged on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: Fuel vapor in a fuel tank (1) is purged into an intake passage (8) of an engine (10) through a purge vent (2, 4, 6). The controller (21) determines whether a leak is present in a purge vent from the fuel tank (1) to a purge control valve (11). The determination process comprises a pull-down process in which a pressure in the purge vent is reduced using a negative pressure in the intake passage (8) and a leak-down process of sealing the purge vent at the reduced pressure and monitoring the pressure variation. The controller (21) calculates an error equivalence amount (DVPII), a pressure component corresponding to sloshing in the fuel tank (1) during the leak-down process, and determines the presence of a leak in a highly accurate manner based a corrected pressure (DVP5A) in which the monitored pressure variation is corrected using the error equivalence amount (DVPII) (S22).

Abstract: To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means 2911 and an estimated fresh air pressure calculated above, and a failure judging means 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: Fuel vapor adsorbed by activated carbon 4a in a canister 4 is introduced to an engine 10 by a manifold vacuum in an intake air passage 8, and burnt. The controller 21 estimates the fuel amount desorbed from the canister 4 during purge, using a canister model (physical model) comprising an equation which computes the adsorption amount and an equation which computes the desorption amount from the adsorption amount and purge rate. An injection pulse width output to injectors 15 is corrected to reduce an air-fuel ratio fluctuation due to the supply of this desorbed fuel to the engine 10.

Abstract: To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means 2911 and an estimated fresh air pressure calculated above, and a failure judging means 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means 2911 and an estimated fresh air pressure calculated above, and a failure judging means 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating device 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating device 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting device 2911 and an estimated fresh air pressure calculated above, and a failure judging device 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: A fuel vapor emission control device of an engine 10 includes a canister 4 which adsorbs fuel vapor generated in a fuel tank 1, and a purge valve 11 which opens and closes a pipe 6 connecting the canister 4 and an intake passage 8 of the engine 10. A controller 21 sets a target purge rate according to a difference between a target air-fuel ratio feedback deviation and an actual air-fuel ratio feedback deviation during purge, and drives the purge valve 11 so that the target purge rate is achieved.

Abstract: Fuel vapor adsorbed by activated carbon 4a in a canister 4 is introduced to an engine 10 by a manifold vacuum in an intake air passage 8, and burnt. The controller 21 estimates the fuel amount desorbed from the canister 4 during purge, using a canister model (physical model) comprising an equation which computes the adsorption amount and an equation which computes the desorption amount from the adsorption amount and purge rate. An injection pulse width output to injectors 15 is corrected to reduce an air-fuel ratio fluctuation due to the supply of this desorbed fuel to the engine 10.

Abstract: A fuel vapor emission control device of an engine 10 includes a canister 4 which adsorbs fuel vapor generated in a fuel tank 1, and a purge valve 11 which opens and closes a pipe 6 connecting the canister 4 and an intake passage 8 of the engine 10. A controller 21 sets a target purge rate according to a difference between a target air-fuel ratio feedback deviation and an actual air-fuel ratio feedback deviation during purge, and drives the purge valve 11 so that the target purge rate is achieved.

Abstract: To provide a failure diagnosis apparatus for an exhaust gas recirculation system which is capable of eliminating the influence of various disturbance factors that vary the suction air pressure, diagnosing a failure of the exhaust gas recirculation system on the basis of the suction air pressure, and preventing wrong diagnosis. A failure diagnosis apparatus for an exhaust gas recirculation system consists of a fresh air pressure estimating means 2911 for calculating an estimated fresh air pressure inside a suction pipe from the operating condition of an internal combustion engine, an actual EGR (exhaust gas recirculation) gas pressure estimating means 2914 for estimating an EGR gas pressure on the basis of a measured suction pipe pressure detected by a suction pipe pressure detecting means 2911 and an estimated fresh air pressure calculated above, and a failure judging means 2910 for judging the failure on the basis of the estimated EGR gas pressure and the detected operating condition.

Abstract: A diagnostic device and method for an exhaust gas recirculation system achieves a prompt diagnosis without reducing accuracy. The diagnosis of an exhaust gas recirculation system, which is carried out based on an EGR temperature and an operating signal for operating an EGR control valve, is prevented when the EGR temperature is greater than a predetermined temperature, except when a rising rate of the EGR temperature is greater than a predetermined value.