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 a cold-start of the engine,closing an exhaust throttle, disposed downstream of the exhaust catalyst, and an EGR valve while diverting at least a portion of throttled exhaust gas through an EGR cooler and then through a bypass passage joined to an EGR passage at a junction,wherein the EGR cooler is coupled to an exhaust passage upstream of the throttle,wherein the EGR valve is coupled to the EGR passage downstream of the junction, andwherein the EGR cooler is in thermal communication with a coolant system, the coolant system in thermal communication with the engine.
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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:
during a cold-start of the engine, closing an exhaust throttle, disposed downstream of the exhaust catalyst, and an EGR valve while diverting at least a portion of throttled exhaust gas through an EGR cooler and then through a bypass passage joined to an EGR passage at a junction, wherein the EGR cooler is coupled to an exhaust passage upstream of the throttle, wherein the EGR valve is coupled to the EGR passage downstream of the junction, and wherein the EGR cooler is in thermal communication with a coolant system, the coolant system in thermal communication with the engine. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for an engine, comprising:
during a cold-start of the engine, restarting the engine with each of a post-catalyst exhaust throttle and an EGR valve closed; with the EGR valve and exhaust throttle closed, diverting at least a portion of throttled exhaust gas around the exhaust throttle via an EGR cooler and an ejector, where the diverted portion of throttled exhaust gas is not recirculated to an engine intake; and maintaining each of the throttle and the EGR valve closed until an EGR cooler outlet temperature is above a threshold, wherein the EGR cooler is in thermal communication with a coolant system, the coolant system in thermal communication with the engine. - 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, opening the exhaust throttle for a predetermined duration in response to an exhaust back-pressure 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 EGR 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, where the EGR valve is located in the EGR passage downstream of a location where the branch passage couples to the EGR passage; and a controller including a non-transitory computer-readable medium with 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, where the exhaust gas is not recirculated to the engine intake; 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 EGR cooler and then through the ejector; and during both the first mode and the second mode, drawing vacuum with a neck of the ejector disposed in the branch passage. - View Dependent Claims (19, 20)
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Specification