In an exhaust secondary air supply system including an electric air pump and a flow rate control valve disposed in an air supply passage connected to an exhaust passage of an engine, the electric air pump is first driven after the start of the engine, and the flow rate control valve is then opened after a lapse of a predetermined time. At a time after starting the driving of the electric air pump, the abnormality of the electric air pump is detected by comparing a deviation between the current before and after driving of the electric air pump with a predetermined reference value. After opening of the flow rate control valve, the abnormality of the flow rate control valve is detected by comparing the deviation between the current before and after the opening of the flow rate control valve with a predetermined reference value.
A method for operating an electro motor-driven secondary air pump which is provided for injecting secondary air into the exhaust system of an internal combustion engine. The secondary air pump is operated in a clocked manner. The induced voltage at the electro motor of the secondary air pump, measurable during the turn-off time of the clocked operation, is used for diagnosing as well as for controlling the speed of the secondary air pump. The diagnosis is carried out based on the evaluation of a parameter (difference quotient, differential quotient) of the induced voltage. The induced voltage is instantaneously a measure for the secondary air pump's actual speed value, so that a separate detection of the actual speed value is omitted.
A secondary air control system supplies secondary air to the upstream of a catalyst purifying exhaust gas in an exhaust passage of an engine. A diagnostic device includes a secondary air detecting means that detects a secondary air information related to pressure of secondary air. An abnormality diagnostic means performs an abnormality diagnostic operation of the secondary air control system in accordance with the secondary air information. A voltage detecting means that detects a power source voltage information related to power source voltage supplied to the secondary air control system. An evaluating condition correcting means that corrects an evaluating condition, which is used for evaluating abnormality in the secondary air control system in accordance with a power source voltage information.
There is provided a device for supplying secondary air, which comprises a secondary air passage for supplying secondary air, to an exhaust passage of an engine, upstream of an exhaust purification device provided in the exhaust passage, a pump provided in the secondary air passage for supplying a secondary air, a battery used for driving the pump, at least one opening-closing device for opening and closing the secondary air passage, and a pressure sensor provided between the pump and the opening-closing device for detecting a pressure in the secondary air passage. A malfunction of at least one of the pump and the opening-closing device is detected on the basis of at least one of the pressures detected when the secondary air passage is opens and when the secondary air passage is closed. The malfunction detection is ceased when the voltage of the battery changes by a value larger than a predetermined value when the pressure sensor detects a malfunction of the pressure variation in the secondary air passage for detecting a malfunction of at least one of the pump and the opening-closing device.
A secondary air pipe is connected on the upstream side from catalyst in an exhaust pipe, and a secondary air pump is provided at an upstream portion of the secondary air pipe. An opening/closing valve for opening/closing the secondary air pipe is provided on the downstream side from the secondary air pump. A pressure sensor for detecting pressure within pipe is provided between the secondary air pump and the opening/closing valve. An ECU calculates a secondary airflow rate based upon difference pressure between both secondary air supply pressure which is detected by the pressure sensor when the opening/closing valve is opened under such a condition that the secondary air pump is operated, and also, shutoff pressure which is detected by the pressure sensor when the opening/closing valve is closed.
The invention relates to a secondary air feeding apparatus and a method of detecting an abnormality in the apparatus capable of making a precise determination on abnormalities in components and detecting operational failures as well. According to one aspect of the invention, the opening-closing state of opening-closing means (ASV) is switched during the operation of an air pump, and abnormalities in respective components are detected on the basis of pressure values and pressure fluctuation values detected by a pressure sensor disposed between the air pump and the ASV before and after the switching of the opening-closing means.
