Honda Motor Co., Ltd.

Tomoko Morita

Norio Suzuki

Hiroshi Ohno

Katsuji Wada

Naohiro Sato

Hisao Haga

Takashi Konomoto

Nobuhiro Komatsu

Tadao Nakatsuji

An exhaust emission control device for an internal combustion engine, which is capable of supplying a just enough amount of reducing agent to the NOx catalyst even when a catalyst is provided on an upstream side of the NOx catalyst. A catalyst and a NOx catalyst are disposed at respective upstream and downstream locations in an exhaust system, for purifying NOx and for trapping NOx under an oxidizing atmosphere and reducing the NOx under a reducing atmosphere, respectively. An air-fuel sensor is disposed between the catalyst and the NOx catalyst. A reducing agent is supplied to an upstream side of the catalyst, to control exhaust gases such that the gases form the reducing atmosphere. To determine time of termination of NOx reduction control, an amount of reducing agent supplied to the NOx catalyst is calculated, and calculation of the amount of reducing agent is started when the air-fuel ratio has converged within a vicinity of a target air-fuel ratio.

Exhaust emission control device and method for internal combustion engine, and engine control unit

An exhaust emission control device for an internal combustion engine which is capable of supplying a just enough amount of reducing agent to a NOx catalyst while causing the consumption amount of reducing agent dependent on the degradation degree of an upstream catalyst to be reflected thereon. A NOx catalyst is disposed at a location downstream of a catalyst having an oxidation function for purifying exhaust gases, for trapping NOx contained in exhaust gases in an oxidizing atmosphere, and reducing the trapped NOx in a reducing atmosphere to thereby purify the trapped NOx. Exhaust gases flowing into the NOx catalyst are controlled to the reducing atmosphere, by supplying reducing agent to an upstream side of the catalyst. The degradation degree of the catalyst is estimated, and a time period over which the reduction control should be executed is corrected according to the estimated degradation degree.

An exhaust control device for an internal combustion engine, comprises: a NOx purifying catalyst disposed in an exhaust system; and a rich control means for calculating a fuel injection amount based on a difference between a target exhaust air fuel ratio and an actual exhaust air fuel ratio to feedback-control the actual exhaust air fuel ratio so that a reducing atmosphere is created in the exhaust system to thereby reduce NOx trapped by the NOx purifying catalyst, wherein the rich control means includes a learning means for calculating and updating a control correction value of the fuel injection amount based on an actual control value of the fuel injection amount during the feedback control, and wherein the fuel injection amount is calculated during the feedback control by using the control correction value.

Exhaust control device for an internal combustion engine

An exhaust emission control device for an internal combustion engine, which is capable of accurately estimating the amount of NOx trapped by a NOx catalyst even when a catalyst is provided on an upstream side of the NOx catalyst. A catalyst having the function of purifying NOx and a NOx catalyst for trapping NOx under an oxidizing atmosphere are disposed in an exhaust system. The amount of NOx contained in exhaust gases is estimated. A NOx purification performance of the catalyst is calculated. The NOx emission amount is corrected based on the purification performance. An amount of NOx trapped in the NOx catalyst is calculated based on the corrected NOx emission amount. A reducing agent is supplied to an upstream side of the catalyst based on the trapped NOx amount, thereby causing the NOx catalyst to carry out a NOx reducing operation.

In a control device for an internal combustion engine provided with a NOx catalytic converter in an exhaust passage thereof, the progress of an undesired substance removal process is computed from the consumption of the reducing agent contained in the exhaust gas in the NOx catalytic converter. The undesired substance may include sulfur contents and NOx captured in the NOx catalytic converter. This computation may be based on the air fuel ratio of the exhaust gas upstream of the NOx catalytic converter and the estimated consumption of the reducing agent contained in the exhaust gas or on the difference between the air fuel ratios of the exhaust gas upstream and downstream of the NOx catalytic converter. In either case, the accuracy can be improved by taking into account the space velocity of the exhaust gas.

Sulfur purge control device for an internal combustion engine

An exhaust gas purifying device for an internal combustion engine, comprises: an exhaust purifying catalyst; a NOx purifying catalyst disposed downstream of the exhaust purifying catalyst; upstream and downstream A/F detecting sensors disposed on upstream and downstream sides of the exhaust purifying catalyst, respectively; means for supplying a reducing agent to the NOx purifying catalyst when conducting a reduction control of the NOx; means for calculating an amount of reduced NOx in the NOx purifying catalyst; means for terminating the reduction control when the amount of reduced NOx exceeds a prescribed reduction termination threshold value; means for detecting a degree of deterioration of the exhaust purifying catalyst based on an output from the upstream and downstream A/F detecting sensors; a threshold value correcting means for correcting the reduction termination threshold value according to the degree of deterioration of the exhaust purifying catalyst; and a correction prohibiting means for prohibiting the correction of the reduction termination threshold value when an amount of Hand/or CHin the exhaust gas exceeds a prescribed correction prohibiting judgment value.

Exhaust gas purifying device for an internal combustion engine

An exhaust gas purifying device for an internal combustion engine, comprises: a first catalyst (TWC, example) having a reducing capability; a second catalyst (LNC, example) provided downstream of the first catalyst, the second catalyst is adapted to trap NOx in a lean condition of air fuel ratio of an exhaust gas and reduce the trapped NOx in a rich condition of air fuel ratio of the exhaust gas; and an exhaust air fuel ratio control means for controlling an exhaust air fuel ratio to decrease the NOx in the first and second catalysts, wherein the exhaust air fuel ratio control means conducts NOx decreasing control suitable for the first catalyst when the second catalyst is in an inactive state and the first catalyst is in an active state, and wherein the exhaust air fuel ratio control means conducts NOx decreasing control suitable for the second catalyst after the second catalyst is activated.

An exhaust emission control device for an internal combustion engine, which is capable of supplying a just enough amount of reducing agent to a NOx catalyst, thereby reducing exhaust emission and improving fuel economy. The device includes a three-way catalyst, a NOx catalyst provided downstream of the three-way catalyst, and an ECU. The ECU carries out rich spike control such that exhaust gases flowing into the NOx catalyst form a reducing atmosphere. During the control, the ECU calculates a reducing agent consumption amount of reducing agent in the exhaust gases consumed by the three-way catalyst, calculates a cumulative reducing agent amount as a total amount of reducing agent supplied to the NOx catalyst, depending on the reducing agent consumption amount, and terminates the control when the cumulative reducing agent amount becomes larger than a predetermined value.

An exhaust emission control device which is capable of supplying a just enough amount of reducing agent to a NOx catalyst while causing the amount of reducing agent consumed in an upstream catalyst to be reflected thereon. A NOx catalyst for trapping NOx and reducing NOx to change the same into harmless ingredients in a reducing atmosphere is disposed downstream of a catalyst. Reducing agent is supplied upstream of the catalyst to cause the NOx catalyst to perform a NOx-reducing action. The amount of oxygen occluded in the catalyst is calculated. During reduction control, according to the oxygen occlusion amount, the amount of reducing agent oxidized and consumed in the catalyst is calculated. According to the reducing agent consumption amount, the amount of reducing agent supplied to the NOx catalyst is calculated. The reduction control is terminated based on the reducing agent supply amount.

The invention provides a catalyst for catalytic reduction of nitrogen oxides contained in exhaust gases wherein fuel is supplied and subjected to combustion under periodic rich/lean conditions and the resulting exhaust gases are brought into contact therewith, which catalyst comprises: (A) a catalyst component A comprising (c) ceria or (d) praseodymium oxide or (e) an oxide and/or a composite oxide of at least two elements selected from the group consisting of cerium, zirconium, praseodymium, neodymium, terbium, samarium, gadolinium and lanthanum; (B) a catalyst component B comprising (d) a noble metal catalyst component selected from the group consisting of platinum, rhodium, palladium and oxides thereof and (e) a carrier; and (C) a catalyst component C comprising (f) a solid acid, and (g) a solid acid supporting an oxide of at least one element selected from the group consisting of vanadium, tungsten, molybdenum, copper, iron, cobalt, nickel and manganese.

Catalyst and method for catalytic reduction of nitrogen oxides

An exhaust gas purifying apparatus for an internal combustion engine having an exhaust system. The apparatus includes a NOx purifying device provided in the exhaust system. This device removes NOx from exhaust gases when a concentration of oxygen in the exhaust gases is higher than a concentration of reducing components in the exhaust gases; generates ammonia and retains the generated ammonia when the concentration of reducing components in the inflowing exhaust gases is higher than the concentration of oxygen; and purifies NOx with the retained ammonia when the concentration of reducing components in the inflowing exhaust gases is lower than the concentration of oxygen. A residual amount of ammonia retained in the NOx purifying device is estimated. The concentration of reducing components in the exhaust gases is switched with respect to the concentration of oxygen according to the estimated residual amount.

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Wako, Japan

Tomoko Morita