摘要:
An engine comprising an exhaust passage having therein a NO.sub.x absorbent which absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorbent is lean and releases the absorbed NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorbent becomes the stoichiometric air-fuel ratio or rich. When the air-fuel ratio of the air-fuel mixture should be changed over from lean to the stoichiometric air-fuel ratio, the air-fuel ratio of the air-fuel mixture is temporarily made rich and is then made the stoichiometric air-fuel ratio.
摘要:
The exhaust gas purification device includes a NO.sub.x absorbent disposed in an exhaust gas passage of an internal combustion engine. The engine is mainly operated at a lean air-fuel ratio. The NO.sub.x absorbent absorbs NO.sub.x in the exhaust gas from the engine when the exhaust gas flowing into the NO.sub.x absorbent is at a lean air-fuel ratio, and releases the NO.sub.x absorbed therein and reduces it when the air-fuel ratio of the exhaust gas becomes a rich air-fuel ratio. A control circuit is provided for controlling the operating air-fuel ratio of the engine. When the ignition switch of the engine is turned off, the control circuit continues the engine operation for a predetermined period before terminating the engine operation. During this engine operation, the operating air-fuel ratio of the engine is controlled at a rich air-fuel ratio to supply exhaust gas with a rich air-fuel ratio to the NO.sub.x absorbent. Therefore, NO.sub.x absorbed and held therein when the ignition switch is turned off is released and reduced by the rich air-fuel ratio exhaust gas from the engine. Since the NO.sub.x absorbent is maintained at the condition where no NO.sub.x remains in the NO.sub.x absorbent after the engine has stopped, unreduced NO.sub.x is not released from the NO.sub.x absorbent even if the NO.sub.x absorbent is cooled after the engine has stopped.
摘要:
An apparatus for, and a method of, purifying exhaust gas emitted from an internal combustion engine reduces fuel consumption under a lean operating condition and generates high torque under a rich operating condition without deteriorating the cleanness of exhaust gas and the driveability of the engine. The apparatus and method improve the durability of a variable valve timing mechanism of the engine. The engine operation involves lean and rich operating conditions. The variable valve timing mechanism of the apparatus changes the open and close timing of at least one of intake and exhaust valves of the engine. The apparatus further has a catalytic converter in an exhaust system, to occlude NOx under the lean operating condition and discharge and reduce the occluded NOx under the rich operating condition. The apparatus also has a prohibition unit for prohibiting the variable valve timing mechanism from changing the valve open and close timing of the valves when the air-fuel ratio of the engine is changed from lean to rich to discharge and reduce the occluded NOx.
摘要:
An NO.sub.x absorber (18) is arranged in an exhaust passage of an internal combustion engine. The NO.sub.x absorber (18) absorbs the NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) is lean while releases the absorbed NO.sub.x when the air-fuel ratio of the exhaust gas flowing into the NO.sub.x absorber (18) becomes the stoichiometric air-fuel ratio or rich. An air-fuel ratio sensor (22) is arranged in the exhaust passage downstream of the NO.sub.x absorber (18). When the air-fuel ratio detected by the air-fuel ratio sensor (22) is switched from lean to rich after the air-fuel ratio of the exhaust gas flowing into NO.sub.x absorber (18) is switched from lean to rich, it is decided that the releasing action of NO.sub.x from the NO.sub.x absorber (18) is completed.
摘要:
An NOx absorbent is installed in an exhaust conduit of an internal combustion engine capable of fuel combustion at lean air-fuel ratios. An oxygen concentration is repeatedly or continuously decreased by, for example, switching the air-fuel from the lean air-fuel ratio to a stoichiometric or rich air fuel ratio when the exhaust gas temperature is higher than 550.degree. C. or when NOx absorbent temperature is higher than 500.degree. C. As a result, the SOx absorbed in the NOx absorbent during lean air-fuel ratio, low temperature operation is released from the NOx absorbent, and the SOx-poisoned NOx absorbent is recovered.
摘要:
A NOx absorbent (18) is disposed in an exhaust passage (17) of an internal combustion engine (1), and a control circuit (30) is provided for controlling the amount of fuel injection into the engine (1). The control circuit 30 works to operate the engine at a rich air-fuel ratio by increasing the amount of fuel supply to the engine so that NOx absorbed by the NOx absorbent when the engine was last stopped is released in all amounts and is purified by reduction after the start of the engine until the engine is first operated at a lean air-fuel ratio. This prevents the release of unpurified NOx from the NOx absorbent (18) at the start of the engine. The operation at a lean air-fuel ratio is assumed in a state where almost no NOx has been absorbed by the NOx absorbent (18), enabling the absorbing capacity of the NOx absorbent to be utilized to the maximum degree.
摘要:
An exhaust gas purification device of an engine providing a NO.sub.x absorbent arranged in the exhaust passage. An O.sub.2 sensor is arranged in the engine exhaust passage downstream of the NO.sub.x absorbent. The degree of deterioration of the NO.sub.x absorbent is detected from the output signal of the O.sub.2 sensor. The cycle for making the air-fuel ratio of the air-fuel mixture rich for causing the release of the NO.sub.x from the NO.sub.x absorbent and the rich time at that time are shortened the greater the deterioration of the NO.sub.x absorbent.
摘要:
An exhaust purification device of an engine providing a NO.sub.x absorbent arranged in the exhaust passage. An O.sub.2 sensor generating a current proportional to the air-fuel ratio is arranged in the engine exhaust passage downstream of the NO.sub.x absorbent. The amount of NO.sub.x actually absorbed in the NO.sub.x absorbent at the time of release of the NO.sub.x is calculated on the basis of the output signal of this O.sub.2 sensor. On the basis of this calculated amount of NO.sub.x, correction is made so that the estimated amount of NO.sub.x represents the actual amount of absorption of NO.sub.x. When this corrected estimated amount of NO.sub.x reaches a set value, the action of releasing the NO.sub.x from the NO.sub.x absorbent is carried out.
摘要:
An exhaust purification device which is capable of detecting the degree of deterioration of the NOx absorbent or the three-way catalyst arranged in the exhaust passage of an engine. An O.sub.2 sensor whose output current or output voltage is proportional to the air-fuel ratio is arranged inside the exhaust passage downstream of the NOx absorbent or three-way catalyst. The air-fuel ratio of the air-fuel mixture is temporarily changed from lean to rich or from rich to lean to enable the degree of deterioration of the NOx absorbent or three-way catalyst to be detected from the peak value of the output current or voltage of the O.sub.2 sensor during the time when the air-fuel ratio is changed.
摘要:
A device for detecting deterioration of a NO.sub.x absorbent arranged in the exhaust passage of an engine. An O.sub.2 sensor generating a current proportional to the air-fuel ratio is arranged in the exhaust passage downstream of the NO.sub.x absorbent. When the amount of NO.sub.x absorbed in the NO.sub.x absorbent is almost zero or after the amount of NO.sub.x absorbed in the NO.sub.x absorbent is made almost zero, the air-fuel ratio of the air-fuel mixture is changed from lean to rich, and the amount of oxygen stored in the NO.sub.x absorbent is detected from the output signal of the O.sub.2 sensor at this time. Further, the NO.sub.x absorbing capability is found by using this detected oxygen amount.