Exhaust gas purifying device for engine
First Claim
1. An exhaust gas purifying device for an engine having an exhaust passage comprising:
- an exhaust gas purifying catalyst arranged in the exhaust passage wherein a NOX adsorbing capacity of the exhaust gas purifying catalyst increases as a temperature of the exhaust gas purifying catalyst decreases, and wherein when the catalyst temperature increases toward a first threshold temperature, the NOX previously adsorbed therein is desorbed therefrom, wherein, at the first threshold temperature, the NOX adsorbing capacity of the exhaust gas purifying catalyst is substantially zero; and
catalyst temperature control means for controlling the catalyst temperature, the catalyst temperature control means alternately and repeatedly decreasing the catalyst temperature below and increasing the catalyst temperature above the first threshold temperature to adsorb NOX therein when the catalyst temperature falls below the first threshold temperature, and to desorb therefrom NOX previously adsorbed therein when the catalyst temperature increases above the first threshold temperature, wherein the desorbed NOX is reduced.
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Accused Products
Abstract
An exhaust gas purifying device for an engine comprises an exhaust gas purifying catalyst with an electric heater arranged in the exhaust passage capable of temporarily adsorbing NOX in the inflowing exhaust gas therein. A NOX adsorbing capacity of the exhaust gas purifying catalyst becomes larger when a temperature of the exhaust gas purifying catalyst becomes higher. The heater is turned on and is turned off alternately and repeatedly to thereby increase and reduce the catalyst temperature. NOX in the inflowing exhaust gas is adsorbed in the exhaust gas purifying catalyst when the catalyst temperature falls, and the adsorbed NOX is desorbed from the exhaust gas purifying catalyst and reduced when the catalyst temperature increases. The catalyst temperature is controlled to increase to a first upper threshold temperature, at which the NOX adsorbing capacity of the exhaust gas purifying catalyst is substantially zero, and is controlled to fall to a first lower threshold temperature, at which the NOX adsorbing capacity of the exhaust gas purifying catalyst is substantially a maximum.
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Citations
27 Claims
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1. An exhaust gas purifying device for an engine having an exhaust passage comprising:
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an exhaust gas purifying catalyst arranged in the exhaust passage wherein a NOX adsorbing capacity of the exhaust gas purifying catalyst increases as a temperature of the exhaust gas purifying catalyst decreases, and wherein when the catalyst temperature increases toward a first threshold temperature, the NOX previously adsorbed therein is desorbed therefrom, wherein, at the first threshold temperature, the NOX adsorbing capacity of the exhaust gas purifying catalyst is substantially zero; and catalyst temperature control means for controlling the catalyst temperature, the catalyst temperature control means alternately and repeatedly decreasing the catalyst temperature below and increasing the catalyst temperature above the first threshold temperature to adsorb NOX therein when the catalyst temperature falls below the first threshold temperature, and to desorb therefrom NOX previously adsorbed therein when the catalyst temperature increases above the first threshold temperature, wherein the desorbed NOX is reduced. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An exhaust gas purifying device for an engine having an exhaust passage comprising:
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an exhaust gas purifying catalyst arranged in the exhaust passage wherein a NOX adsorbing capacity of the exhaust gas purifying catalyst increases as a temperature of the exhaust gas purifying catalyst becomes lower, wherein when the catalyst temperature decreases toward a first threshold temperature, NOX previously adsorbed therein is desorbed therefrom, and wherein, at the first threshold temperature, the NOX adsorbing capacity of the exhaust gas purifying catalyst is a maximum amount; and catalyst temperature control means for controlling the catalyst temperature, the catalyst temperature control means alternately and repeatedly decreasing the catalyst temperature to and increasing the catalyst temperature above the first threshold temperature to adsorb NOX therein when the catalyst temperature falls to the first threshold temperature, and to desorb therefrom NOX previously adsorbed therein when the catalyst temperature increases above the first threshold temperature, wherein the desorbed NOX is reduced. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. An exhaust gas purifying device for an engine having an exhaust passage comprising:
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an exhaust gas purifying catalyst arranged in the exhaust passage wherein a NOX adsorbing capacity of the exhaust gas purifying catalyst decreases as a temperature of the exhaust gas purifying catalyst becomes higher and wherein the NOX absorbing capacity of the exhaust gas purifying catalyst decreases as the catalyst temperature rises above a first lower threshold temperature to a substantially zero level of NOX absorbing capacity at a first upper threshold temperature, wherein the first upper threshold temperature is higher than the first lower threshold temperature so that, as the catalyst temperature increases above the first lower threshold temperature toward the first upper threshold temperature, NOX previously adsorbed therein is desorbed therefrom, wherein, at the first lower threshold temperature, the NOX adsorbing capacity of the exhaust gas purifying catalyst is a maximum amount; and catalyst temperature control means for controlling the catalyst temperature, the catalyst temperature control means alternately and repeatedly decreasing the catalyst temperature to the first lower threshold temperature and increasing the catalyst temperature to the first upper threshold temperature to adsorb NOX therein when the catalyst temperature falls toward the first lower threshold temperature, and to desorb therefrom NOX previously adsorbed therein when the catalyst temperature increases toward the first upper threshold temperature, wherein the desorbed NOX is reduced. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
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Specification