| 摘要 |
Dosing components (22, 24, 32) in an engine exhaust after-treatment system (18) that includes an SCR catalyst (20) are thermally managed by flowing engine coolant through a coolant passage in a urea injector (22) that injects aqueous urea into the after-treatment system, controlling a three-way valve (60) to selectively direct coolant flow leaving the urea injector to a first branch that is in heat exchange relationship with a tank (24) that holds a supply of aqueous urea and a supply pump module (32) that pumps aqueous urea from the tank to the urea injector, and a second branch that is not in heat exchange relationship with either the tank or the supply pump, and returning coolant from the branches to the engine cooling system.
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