Abstract: Fuel-vapor evaporating from a fuel tank is led through a vapor pipe and absorbed in a charcoal canister. Fuel-vapor stored in the charcoal canister is supplied to an inlet pipe when a purge valve is opened when the engine is driven, because the pressure in the inlet pipe is low. Fuel-vapor is then burned as fuel in the engine. If the opening of the purge valve is suddenly increased at the start of the purge, the air fuel ratio control is disturbed. Therefore, the purge rate is gradually increased and the vapor concentration of the fuel-vapor purged from the charcoal canister is learned, and the change rate of the purge rate is made small because the air-fuel ratio control may be disturbed when the vapor concentration is not learned enough.

Abstract: An altitude determining apparatus for an automotive vehicle includes a calculating part for determining a reference flow rate based on a throttle angle of a throttle valve and an engine speed of an internal combustion engine of the vehicle, the throttle angle being sensed from the throttle valve arranged in an intake passage of the engine and the engine speed being sensed from the engine, a correction part for detecting an operating condition under which additive gas is supplied to the intake passage downstream of the throttle valve and for changing the reference flow rate determined by the calculating part to a second reference flow rate according to the operating condition only when the above mentioned operating condition is detected, and a discriminating part for comparing an intake air flow rate sensed at an inlet portion of the intake passage with a reference flow rate supplied from the correction part and for determining an altitude condition of the vehicle based on the result of the comparison.

Abstract: An air-fuel ratio control apparatus includes: a determining part for determining a target purge ratio in accordance with operating conditions of an engine; a purge control part for controlling a flow rate of evaporated fuel, supplied from an evaporated fuel purge system into an intake passage of the engine, by actuating a purge control valve based on the target purge ratio, and for storing an evaporated fuel flow rate of the purge control valve; a fuel injection control part for generating a drive signal in accordance with a fuel injection time, and for controlling an air-fuel ratio of an air-fuel mixture to the intake passage by actuating a fuel injection valve in accordance with the drive signal; an estimating part for estimating the ratio of an evaporated fuel flow rate to an intake air flow rate based on sensed operating conditions of the engine and on the stored evaporated fuel flow rate of the purge control part; and a fuel injection time determining part for determining a fuel injection time based on t

Abstract: The present invention provides an improved air-fuel ratio control system which eliminates a time lag of outputs of an outlet or second oxygen sensor at a high accuracy and adequately controls the air-fuel ratio, thus efficiently reducing an exhaust of harmful gases including HC, CO, and NOx and improving the fuel consumption. When an output voltage SOX of the second oxygen sensor is within a predetermined range between a first voltage E1 and a second voltage E2 including a reference voltage E0 corresponding to a stoichiometric air-fuel ratio, an update quantity DRSR of a rich skip amount RSR is equal to zero. When the output voltage SOX is in a range between a minimum output GSOXmin and the first voltage E1, the update quantity DRSR exponentially increases with the decrease in the voltage. When the output voltage SOX is in a range between the second voltage E2 and a maximum output GSOXmax, the update quantity DRSR exponentially decreases with the increase in the voltage.

Abstract: An apparatus for controlling a heater for an oxygen sensor includes a heater controller for detecting a heater resistance value of a heater and for controlling the heater so that a detected resistance value of the heater is equal to a target resistance value. A specific operating condition detecting unit detects a specific operating condition of the internal combustion engine where the air-fuel ratio is other than a stoichiometric air-fuel ratio. A target resistance value changing unit changes the target resistance value when the air-fuel ratio in the specific operating condition indicated by the sensor output signal is s outside a normal range of air-fuel ratio which should be detected in the specific operating condition.

Abstract: An apparatus for controlling a heater for an oxygen sensor which includes a heater resistance value detecting unit for detecting a heater resistance value of the heater, the power control unit for controlling a power supplied to the heater so that the heater resistance value is equal to a target resistance value, and a target resistance value setting unit for calculating a rate of change in the heater resistance value of the heater measured by the heater resistance value detecting unit, and for determining the target resistance value on the basis of the rate of change in the heater resistance value.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Also, a learning correction amount is calculated so that a mean value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In an internal combustion engine having an air-fuel ratio sensor in an exhaust pipe thereof and a signal processing circuit for an output of the air-fuel ratio sensor, a air-fuel ratio correction amount is regulated within a range defined by a lower limit value and a upper limit value, and the air-fuel ratio of the engine is adjusted by the air-fuel ratio correction amount, and one of the limit values is varied in accordance with a running state parameter of the engine.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. Also, when the output of the upstream-side air-fuel ratio sensor is in an abnormal state, an alarm is generated.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an air-fuel ratio correction amount is calculated in accordance with the results of the comparison of the outputs of the upstream-side and downstream-side air-fuel ratio sensors with first and second reference voltages, respectively, thereby obtaining an actual air-fuel ratio. The second reference voltage is changed in accordance with the load of the engine, to change the mean air-fuel ratio.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. A center value of an air-fuel ratio correction amount or an air-fuel ratio feedback control parameter calculated based upon the output of the downstream-side air-fuel ratio sensor is calculated by a learning control for regions defined by the period of the output of the upstream-side air-fuel ratio sensor, and an air-fuel ratio feedback control is initiated by using the center value stored for the current region when the engine enters into an air-fuel ratio feedback control state, or when the period of the output of the upstream-side air-fuel ratio sensor is transferred to a different region.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Also, a learning correction amount is calculated so that an integration amount of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. A center value of an air-fuel ratio correction amount or an air-fuel ratio feedback control parameter calculated based upon the output of the downstream-side air-fuel ratio sensor is calculated by a learning control, and an air-fuel ratio feedback control is initiated by using the center value when the engine enters into an air-fuel ratio feedback control state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors. Also, when the output of the upstream-side air-fuel ratio sensor is in an abnormal state, an alarm is generated.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side air-fuel ratio sensor and the downstream-side air-fuel ratio sensor. The adjustment of the air-fuel ratio by the downstream-side air-fuel ratio sensor is stopped when the engine is in a predetermined state.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, a delay operation is performed upon the output of the downstream-side air-fuel ratio sensor, so that the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side air-fuel ratio sensor and the delayed output of the downstream-side air-fuel ratio sensor.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, an actual air-fuel ratio is adjusted in accordance with the outputs of the upstream-side and downstream-side air-fuel ratio sensors including an air-fuel ratio correction amount. Accordingly, only when the change of the intake air density is large, is a learning correction amount calculated so that a means value of the air-fuel ratio correction amount is brought close to a reference value. The actual air-fuel ratio is further adjusted in accordance with the learning correction amount.

Abstract: In a double air-fuel sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust gas passage, the actual air-fuel ratio is adjusted in accordance with the output of the upstream-side and downstream-side air-fuel ratio sensors. For a predetermined time period after the engine enters an air-fuel ratio feedback control for the downstream-side air-fuel ratio sensor, the control speed by the downstream-side air-fuel ratio sensor is increased.

Abstract: In a double air-fuel ratio sensor system including two air-fuel ratio sensors upstream and downstream of a catalyst converter provided in an exhaust passage, the actual air-fuel ratio is adjusted in accordance with an air-fuel ratio correction amount calculated by using the output of the upstream-side air-fuel ratio sensor and an air-fuel ratio feedback control parameter such as delay time periods, skip amounts, or integration amounts calculated by using the output of the downstream-side air-fuel ratio sensor, and the calculation of the air-fuel ratio feedback control parameter is prohibited when the downstream-side air-fuel ratio sensor is in an abnormal state.