Patent ID: 8413434

Claim:
An exhaust heat recovery system (EHRS) for a vehicle with an engine, a transmission with a transmission heat exchanger, and an exhaust system through which exhaust gas is discharged from the engine, comprising: an exhaust heat recovery device positioned in the exhaust system and that has an exhaust heat recovery device heat exchanger (EHRDHE) and a bypass valve operable in a first position to direct exhaust gas through the EHRDHE and in a second position to bypass the EHRDHE; a plurality of coolant flow passages defining a first circuit directing coolant flow from the EHRDHE to the engine, a second circuit directing coolant flow to the engine and that bypasses the EHRDHE, and a third circuit that directs coolant flow from the EHRDHE to the transmission heat exchanger and is not in fluid communication with the engine; a plurality of coolant temperature sensors operable to sense temperature of the coolant in the circuits; at least one valve operable to direct coolant flow to the first circuit when coolant temperature in the first circuit is less than a first predetermined temperature, to thereby warm the engine using the exhaust heat, and to direct coolant flow to the second circuit when coolant temperature of the engine is greater than the first predetermined temperature; wherein the at least one valve includes a first valve downstream of the engine and upstream of the EHRDHE and selectively operable to direct coolant flow to the first circuit and alternately to the second circuit; wherein the at least one valve includes a second valve and a third valve downstream of the EHRDHE and operable to direct coolant flow from the EHRDHE through the second valve to the transmission heat exchanger and then through the third valve to the engine when the coolant temperature downstream of the EHRDHE is greater than a third predetermined temperature and less than the first predetermined temperature; a pump positioned to pump coolant in the third circuit and controllable to pump the coolant when the coolant temperature in the third circuit is greater than the first predetermined temperature and less than a second predetermined temperature; wherein the second predetermined temperature is greater than the first predetermined temperature so that the transmission is warmed further by the exhaust heat after warming of the engine is complete; and wherein the second valve and the third valve are operable to direct coolant flow from the EHRDHE to the transmission heat exchanger and back to the EHRDHE through the third circuit without traveling through the first valve when the coolant temperature downstream of the EHRDHE is greater than the first predetermined temperature and less than the second predetermined temperature.