Control method for purging fuel vapor of automotive engine

Claim 3

The method according to claim 1, further comprising: determining the engine is in a steady engine operating condition; changing a duty of purge control valve to change the amount of purging fuel so as to calculate a variation for an air fuel ratio correction coefficient; assuming a canister loading ratio by using a map parameterizing variation of said air-fuel ratio correction coefficient; and determining a purge amount by using a map parameterizing said loading rate.

Claim 4

The method according to claim 1, further comprising: assuming a canister loading ratio by using a formula parameterizing said variation of said air-fuel ratio correction coefficient; and determining a purge amount by using a formula parameterizing said loading rate.

Claim 5

The method according to claim 1, further comprising the steps of: determining a purge amount by using a map parameterizing a change rate of an air-fuel ratio correction coefficient directly.

Claim 6

The method according to claim 1, further comprising the steps of: determining a purge amount by using a formula parameterizing a change rate of an air-fuel ratio correction coefficient directly.

Claim 9

The method according to claim 6, further comprising the steps of: calculating a deviation of air-fuel ratio learning value derived from said canister purge for all addresses at an engine stop; subtracting said calculated deviation value from an air-fuel ratio correction learning value for all addresses; updating said air-fuel ratio correction learning value with said subtracted air-fuel ratio correction learning value for each corresponding address; and holding an electrical power supply to an ECU for a specified time after an engine stop so as to rewrite said an air-fuel ratio correction learning value.

Claim 10

A control method for an canister purge of an internal combustion engine mounted on a vehicle having, an intake pipe for inducing air into a cylinder of said engine, a fuel system for supplying fuel from a fuel tank to said engine, a vapor passage connected between said fuel tank and said intake pipe for purging fuel vapor, a canister provided in said vapor passage for absorbing said fuel vapor, and a purge control valve provided between said canister and said intake pipe for controlling a purge amount of said fuel vapor, an exhaust pipe connected to said cylinder for discharging an exhaust gas, an O 2 sensor inserted in said exhaust pipe for sensing an oxygen concentration in said exhaust gas, an engine speed sensor for detecting an engine speed and for generating an engine speed signal, a temperature sensor for sensing a coolant temperature in a water jacket of said engine and for producing a temperature signal, and a controller responsive to said engine speed and temperature signals for controlling said engine in an optimum condition, the method comprising: judging whether said engine is operated in a steady operating condition or not from said engine speed and temperature signals; stopping a learning control of an air-fuel ratio when said engine is in said steady operating condition; prohibiting a purge control of said fuel vapor to said intake pipe; changing a duty ratio of said purge control valve; calculating a changing amount of said air-fuel ratio corresponding to a changing value of said duty ratio; estimating a canister loading rate dependent on said changing amount; and controlling said purge control valve in order to set said duty ratio at an optimum value derived from a function of said canister loading rate so as to avoid a deviation of said air-fuel ratio from a standard stoichiometric ratio and to effectively improve driveability of said vehicle and emissions performance.

Claim 11

A control method for an canister purge of an internal combustion engine mounted on a vehicle having, an intake pipe for inducing air into a cylinder of said engine, a fuel system for supplying fuel from a fuel tank to said engine, a vapor passage connected between said fuel tank and said intake pipe for purging fuel vapor, a canister provided in said vapor passage for absorbing said fuel vapor, and a purge control valve provided between said canister and said intake pipe for controlling a purge amount of said fuel vapor, an exhaust pipe connected to said cylinder for discharging an exhaust gas, an O 2 sensor inserted in said exhaust pipe for sensing an oxygen concentration in said exhaust gas, an engine speed sensor for detecting an engine speed and for generating an engine speed signal, a temperature sensor for sensing a coolant temperature in a water jacket of said engine and for producing a temperature signal, and a controller responsive to said engine speed and temperature signals for controlling said engine in an optimum condition, the method comprising: judging whether said engine is operated in a steady operating condition or not from said engine speed and temperature signals; stopping a learning control of an air-fuel ratio when said engine is in said steady operating condition; prohibiting a purge control of said fuel vapor to said intake pipe; changing a duty ratio of said purge control valve; calculating a changing amount of said air-fuel ratio corresponding to a changing value of said duty ratio; estimating a canister loading rate dependent on said changing amount; and controlling said purge control valve in order to set said duty ratio at an optimum value derived from a function of said canister loading rate so as to avoid a deviation of said air-fuel ratio from a standard stoichiometric ratio and to effectively improve driveability of said vehicle and emissions performance.