An on-board monitoring system for an automotive emission catalyst [having] has (i) a test chamber remote from the automobile's engine exhaust gas stream; (ii) [means] apparatus for supplying the chamber with sampled exhaust gases sequestered from said stream; (iii) a single hydrocarbon sensor exposed to the exhaust gas in the chamber to render a signal responsive to the concentration of hydrocarbon in the chamber; and (iv) [means] apparatus for comparing the sensed signal with a reference signal, and, if a predetermined difference is exceeded, the catalyst is indicated as faulty. [Means (ii) may have] Apparatus (ii) has a supply channel interconnected between the chamber and the gas stream upstream of the catalytic converter, a supply channel independently interconnected between the chamber and the gas stream downstream of the catalytic converter, and valve [means] apparatus for permitting flow-through of no more than one channel to said chamber at any one moment, preferably cycled at a certain frequency. Method steps Carried Out by the System comprise: [A method of on-board monitoring of an automotive vehicle catalyst, comprising:] (a) periodically transferring a sample quantity of gas from the stream into a test chamber at a predetermined flow rate; (b) exposing a hydrocarbon sensor to the sequestered gas to generate a signal in proportion to the content of hydrocarbon in such gas; and (c) comparing the signal with a reference signal to determine if a predetermined difference exists and thereby conclude the catalyst is sufficiently degraded.
A method for monitoring and controlling the performance of a catalytic converter (34) includes monitoring an exhaust gas stream from an engine (16) for the presence of methane. Upon detecting methane in the exhaust gas stream an oxygen storage level of a catalyst within the catalytic converter (34) is determined. The oxygen storage level is compared with a reference standard and the air/fuel ratio of the exhaust gas stream is continuously adjusted to maintain the oxygen storage level within predetermined control limits.
The invention is directed to a method and an arrangement for monitoring the operation of a hydrocarbon sensor with which the sensor is monitored in a technically simple manner. The method and arrangement preferably utilize existing components of the motor vehicle. The heater power is continuously compared to a pregiven value. A sensor fault is signaled and the heater is shut off when the heater power and the pregiven value do not correspond to each other. The measured hydrocarbon value is compared to emission values to be expected for pregiven operating conditions and a sensor fault is signaled when the measured hydrocarbon value and the emission values do not correspond to each other.
In an exhaust gas purification system for an internal combustion engine including a catalytic converter disposed in an exhaust pipe, an apparatus for controlling an amount and temperature of fresh air fed into the exhaust pipe so that optimal purification efficiency of the catalytic converter can realized. The apparatus includes an air pump for taking in fresh air, a control valve for controlling air flow, a heater for heating the air and the controller for controlling the pump, the valve and the hater in dependence on engine operation states so that nitrogen oxides, carbon monoxide and hydrocarbon contained in the exhaust gas can be removed to a maximum through reduction and oxidation reactions. An abnormality detecting device detects occurrence of abnormality in the air feeding control apparatus for ensuring fail-safe operation thereof.
A device for determining the degree of deterioration of catalyst of a catalytic converter arranged in an internal combustion engine exhaust system is disclosed. The device comprises an O.sub.2 sensor which is arranged in the internal combustion engine exhaust system downstream of the catalytic converter. The O.sub.2 sensor has the low oxidization and deoxidization ability on the detection surface thereof. The device determines the degree of deterioration of the catalyst by comparing a value in connection with an extra O.sub.2 concentration on the basis of a current output of the O.sub.2 sensor in the exhaust gas at a predetermined air-fuel ratio with a basic value.
The invention provides a catalyst deterioration detecting system that is capable of detecting the degree of deterioration of each catalyst in a catalyst converter which includes two or more catalysts in series. The catalyst deterioration detecting system of an internal-combustion engine according to the invention is provided with a upstream catalyst located on an upstream side of an exhaust system of the internal-combustion engine and a downstream catalyst located on a downstream side of the exhaust system. The device comprises an oxygen density detector which is disposed downstream of the downstream catalyst and a deterioration detector for detecting a deterioration degree of the upstream catalyst based on the output of the oxygen density detector. According to an aspect of the invention, the deterioration detector detects deterioration degree of the downstream catalyst based on the previously detected deterioration degree of the upstream catalyst.
