METHOD AND SYSTEM FOR CATALYST TEMPERATURE CONTROL
First Claim
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1. A method for expediting activation of an exhaust catalyst coupled to an engine comprising:
- during an engine cold-start,closing a post-catalyst exhaust throttle while diverting at least a portion of the throttled exhaust gas through an EGR cooler coupled upstream of the throttle.
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Abstract
Methods and systems are provided for controlling and coordinating control of a post-catalyst exhaust throttle and an EGR valve to expedite catalyst heating. By closing both valves during an engine cold start, an elevated exhaust backpressure and increased heat rejection at an EGR cooler can be synergistically used to warm each of an engine and an exhaust catalyst. The valves may also be controlled to vary an amount of exhaust flowing through an exhaust venturi so as to meet engine vacuum needs while providing a desired amount of engine EGR.
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Citations
20 Claims
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1. A method for expediting activation of an exhaust catalyst coupled to an engine comprising:
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during an engine cold-start, closing a post-catalyst exhaust throttle while diverting at least a portion of the throttled exhaust gas through an EGR cooler coupled upstream of the throttle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for an engine, comprising:
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during an engine cold-start, restarting an engine with each of a post-catalyst exhaust throttle and an EGR valve closed; with the valves closed, diverting at least a portion of throttled exhaust gas around the exhaust throttle via an EGR cooler and an ejector; and maintaining each of the throttle and the valve closed until an EGR cooler outlet temperature is above a threshold. - View Dependent Claims (13, 14, 15, 16)
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17. The method of 12, further comprising, while the EGR cooler outlet temperature is below the threshold, intermittently opening the exhaust throttle in response to an exhaust backpressure upstream of the throttle being above a threshold pressure.
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18. An engine system, comprising:
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an engine including an intake and an exhaust; a turbocharger including an intake compressor and an exhaust turbine an exhaust catalyst; a post-catalyst exhaust throttle; an EGR system including an EGR passage, an EGR cooler and an EGR valve, the system fluidly coupling the engine exhaust downstream of the catalyst and upstream of the throttle, to the engine intake, upstream of the compressor; a branch passage including an ejector fluidly coupling an outlet of the EGR cooler to the engine exhaust, downstream of the throttle; and a controller with computer readable instructions for, operating the system in a first mode with each of the throttle and the EGR valve closed and while flowing exhaust gas from the catalyst, through the EGR cooler and then through the ejector; operating the system in a second mode with each of the throttle and the EGR valve open and while flowing exhaust gas from the catalyst, through the ejector and then through the ejector; and during both the first and second mode, drawing vacuum at the ejector. - View Dependent Claims (19, 20)
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Specification