A NO.sub.x absorber catalyst for treating an exhaust gas from a lean burn engine. The NO.sub.x absorber catalyst comprises a molecular sieve catalyst comprising a noble metal and a molecular sieve, wherein the molecular sieve contains the noble metal; an oxygen storage material for protecting the molecular sieve catalyst; and a substrate having an inlet end and an outlet end.

A controlling device for purifying exhaust gas includes: a fuel cutting controller (2) that, if a predetermined condition for fuel cutting is satisfied, shuts off supply of fuel to an engine (10) after a predetermined delay time (B) elapses; a calculator (3) that calculates oxygen occludability of a catalyst (6, 7) being interposed in an exhaust system of the engine (10) and containing an oxygen occludable material; and a setter (4) that sets a length of the delay time (B) in accordance with the oxygen occludability calculated by the calculator (3).

An exhaust purification system includes an LAF sensor provided in an exhaust pipe and generates a signal corresponding to an air-fuel ratio of exhaust gas. An upstream catalytic converter is downstream of the LAF sensor and has a catalyst to purify the exhaust gas. An O2 sensor is downstream of the upstream catalytic converter, and generates a signal corresponding to the air-fuel ratio of the exhaust gas. A GPF is downstream of a the O2 sensor and purifies the exhaust gas. An ECU controls an air-fuel mixture in an engine using output signal KACT of the LAF sensor and an output signal VO2 of the O2 sensor such that the air-fuel ratio of exhaust gas flowing into the GPF converges to a target value near the stoichiometric ratio. The GPF has a filter substrate and a downstream TWC supported by a partition of the filter substrate.

An air-fuel ratio control device switches a target air-fuel ratio from a lean set air-fuel ratio to a rich set air-fuel ratio after judging that an air-fuel ratio of an outflowing exhaust gas has become a stoichiometric air-fuel ratio and an oxygen storage amount of an exhaust purification catalyst has become a switching reference storage amount, and makes an average value of the target air-fuel ratio the stoichiometric air-fuel ratio to less than the lean set air-fuel ratio, from after the estimated value of the oxygen storage amount has become the switching reference storage amount or more until judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio if the estimated value of the oxygen storage amount becomes the switching reference storage amount or more before judging that the air-fuel ratio of the outflowing exhaust gas has become the stoichiometric air-fuel ratio.

In an EHC, a ratio of a heat capacity of the second catalyst body with respect to a heat capacity of the first catalyst body is made within a range of 0.67-1.5. A ratio of an amount of coat of an OSC material in the second catalyst body with respect to an amount of coat of an OSC material in the first catalyst body is made larger than the ratio of the heat capacity of the second catalyst body with respect to the heat capacity of the first catalyst body. A ratio of an amount of support of a noble metal in the second catalyst body with respect to an amount of support of a noble metal in the first catalyst body is made smaller than the ratio of the heat capacity of the second catalyst body with respect to the heat capacity of the first catalyst body.

An internal combustion engine includes an upstream side exhaust purification catalyst and a downstream side exhaust purification catalyst. The control device includes a storage amount estimating device which estimates the oxygen storage amount of the downstream side exhaust purification catalyst, and can execute fuel cut control which cuts the feed of fuel to the combustion chamber during operation of the internal combustion engine when the engine speed is the lowest reference speed or more. The control device lowers the lowest reference speed when the storage amount estimated by the storage amount estimating device has become a given limit storage amount or less, compared with when it is larger than the limit storage amount. As a result, a control device can effectively keep the oxygen storage amount of the downstream side exhaust purification catalyst from decreasing to zero.

An internal combustion engine control device and a catalyst deterioration diagnostic method according to the present invention control the amount of fuel to be supplied to an internal combustion engine such that the air-fuel ratio of the exhaust on the downstream side of the exhaust purification catalyst is alternately switched between rich and lean, measure the oxygen storage capability of the exhaust purification catalyst during a measurement period within a reversal period of the air-fuel ratio, and diagnose deterioration of the exhaust purification catalyst based on a measurement value of the oxygen storage capability. A time point at which the output of an exhaust sensor indicates that the air-fuel ratio of the exhaust on the downstream side of the exhaust purification catalyst begins to change from a vicinity of a stoichiometric air-fuel ratio to rich or lean is set as the time of end of the measurement period.

The present invention relates to a three-way catalytic converter for reducing harmful exhaust components of gasoline-powered internal combustion engines, and to a corresponding method for exhaust gas purification. The catalytic converter is characterized by a particularly inhomogeneous distribution of the oxygen-storing material present.

An oxygen storage/release material includes: a ceria-zirconia composite oxide porous body that has at least one ordered phase of a pyrochlore phase and a ? phase, and that has a central pore diameter of 70 nm to 1 ?m as measured by a mercury penetration method, and in which a cumulative pore volume of pores that each have a pore diameter in the range of 0.5 times to 2 times the central pore diameter is 40% or more of the cumulative pore volume of pores that each have a pore diameter in the range of 10 nm to 10 ?m as measured by the mercury penetration method.

Methods and systems are provided for at least one catalyst and an oxygen filter. In one example, a method may include filtering oxygen through the oxygen filter and flowing oxygen poor exhaust gas to a catalyst.