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OwnerMartyn Twigg, Robert Brisley +1inventors
InventorsMartyn Twigg, Robert Brisley, Daniel Swallow
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A spark ignition engine with an exhaust system having a catalyst, which includes a three-way catalyst (TWC) and a NOx storage component, and an engine control unit is provided. The engine control unit is programmed to control the air-to-fuel ratio of the engine to run at the stoichiometric air-to-fuel ratio during normal running conditions and to run lean of the stoichiometric air-to-fuel ratio during a defined portion of an engine speed/load. The engine control unit also determines the amount of NOx contacting the TWC during lean running operation in response to data input from a sensor means, thereby a remaining NOx storage capacity of the TWC is determined. The control unit is programmed to return the air-to-fuel ratio to stoichiometry when the NOx storage capacity is below a pre-determined value. The engine and its components are arranged such as to substantially prevent passing more NOx to atmosphere during an engine cycle compared with a spark ignition engine run continuously at stoichiometric conditions.
A spark ignition engine comprising an exhaust system comprising a catalyst and an engine control unit programmed to control the air-to-fuel ratio of the engine to run at a stoichiometric air-to-fuel ratio during normal running conditions and to run lean of the stoichiometric air-to-fuel ratio during a defined portion of an engine speed/load map, which catalyst comprising a three-way catalyst (TWC) including a NOx storage component, wherein the engine control unit is programmed to determine an amount of NOx contacting the TWC during lean running operation in response to data input from sensor means, thereby a remaining NOx storage capacity of the TWC is determined, and the control unit is programmed to return the air-to-fuel ratio to stoichiometry when the NOx storage capacity is below a pre-determined value.
An engine control unit for a spark ignition engine comprising an exhaust system comprising a TWC including a NOx storage component, which engine control unit is programmed to control the air-to-fuel ratio of the engine to run at a stoichiometric air-to-fuel ratio during normal running conditions and to run lean of stoichiometry during a defined portion of an engine speed/load map and to determine an amount of NOx contacting the TWC during lean running operation in response to data input from sensor means, thereby a remaining NOx storage capacity of the TWC is determined, and the control unit is programmed to return the air-to-fuel ratio to stoichiometry when the NOx storage capacity is below a pre-determined value.
A method of treating exhaust gas of a spark ignition engine run at the stoichiometric air-to-fuel ratio during normal running conditions, which engine comprising an exhaust system comprising a TWC including a NOx storage component, which method comprising the steps of controlling the engine air-to-fuel ratio to run lean of stoichiometry during a defined portion of an engine speed/load map, determining the amount of NOx contacting the TWC during lean running operation in response to data input from sensor means thereby determining the remaining NOx storage capacity of the TWC, and returning the air-to-fuel ratio to stoichiometry when the remaining NOx storage capacity is below a pre-determined value.
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Dependencies are inferred from the claim text.