Method of flowing coolant through exhaust heat recovery system after engine shutoff

Patent metadata

Field	Value
Publication number	US-2018100711-A1
Application number	US-201615291965-A
Country	US
Kind code	A1
Filing date	Oct 12, 2016
Priority date	Oct 12, 2016
Publication date	Apr 12, 2018
Grant date	—

Abstract

Methods and systems are provided for adjusting a flow of coolant through a coolant system including a rear axle heat exchanger. In one example, a method may include flowing coolant through the coolant system while an engine is not operating. In another example, a method may include increasing a flow of coolant to the rear axle heat exchanger while the engine is not operating when a rear axle oil temperature exceeds a threshold temperature.

First claim

1 . A method, comprising:
flowing coolant through a coolant system while an engine is not operating, while adjusting a flow rate of the coolant through a rear axle heat exchanger (RAHX) in response to a rear axle oil temperature.

2 . The method of claim 1 , wherein adjusting the flow rate of the coolant through the RAHX includes:
responsive to the rear axle oil temperature being greater than a first threshold temperature, maintaining or increasing the flow rate of the coolant through the RAHX; and responsive to the rear axle oil temperature being less than the first threshold temperature, decreasing the flow rate of the coolant through the RAHX.

3 . The method of claim 2 , further comprising adjusting a flow rate of the coolant through a thermal storage vessel (TSV) fluidly coupled with the coolant system in response to a temperature of the TSV.

4 . The method of claim 3 , wherein adjusting the flow rate of the coolant through the TSV includes maintaining or increasing the flow rate of the coolant through the TSV while the temperature of the TSV is less than both of a second threshold temperature and a third threshold temperature.

5 . The method of claim 4 , wherein adjusting the flow rate of the coolant through the TSV includes decreasing the flow rate of the coolant through the TSV while the temperature of the TSV is greater than either of the second threshold temperature or the third threshold temperature.

6 . The method of claim 5 , wherein the second threshold temperature corresponds to a desired storage temperature of the TSV, and wherein the third threshold temperature corresponds to a fluid outlet temperature of an exhaust gas heat exchanger (EGHX) fluidly coupled with the coolant system.

7 . The method of claim 6 , wherein flowing the coolant through the coolant system while the engine is not operating includes maintaining or increasing a coolant pumping rate of a coolant pump fluidly coupled with the coolant system while an amount of time since engine shutoff is less than a threshold amount of time.

8 . The method of claim 7 , wherein flowing the coolant through the coolant system while the engine is not operating includes maintaining or increasing the coolant pumping rate of the coolant pump while the fluid outlet temperature of the EGHX is greater than a fourth threshold temperature.

9 . The method of claim 8 , wherein flowing coolant through the coolant system while the engine is not operating includes decreasing the coolant pumping rate of the coolant pump while the amount of time since engine shutoff is greater than the threshold amount of time and the fluid outlet temperature of the EGHX is less than the fourth threshold temperature.

10 . A method for a coolant system of an engine, comprising:
in response to engine shutoff, flowing coolant through coolant lines fluidly coupled to an exhaust gas heat exchanger (EGHX), a rear axle heat exchanger (RAHX), and a thermal storage vessel (TSV); adjusting a flow rate of the coolant through the RAHX in response to a rear axle oil temperature; and adjusting a flow rate of the coolant through the TSV in response to a temperature of the TSV.

11 . The method of claim 10 , wherein flowing the coolant through the coolant lines includes at least flowing the coolant through the EGHX.

12 . The method of claim 11 , wherein adjusting the flow rate of the coolant through the RAHX in response to the rear axle oil temperature includes maintaining or increasing the flow rate of the coolant through the RAHX while the rear axle oil temperature is above a first threshold temperature and decreasing the flow rate of the coolant through the RAHX while the rear axle oil temperature is below the first threshold temperature.

13 . The method of claim 12 , wherein adjusting the flow rate of the coolant through the TSV in response to the temperature of the TSV includes comparing the temperature of the TSV to both of a second threshold temperature and an EGHX fluid outlet temperature, and maintaining or increasing the flow rate of the coolant through the TSV while the temperature of the TSV is less than both of the second threshold temperature and the EGHX fluid outlet temperature, and decreasing the flow rate of the coolant through the TSV while the temperature of the TSV is greater than one of the second threshold temperature and the EGHX fluid outlet temperature.

14 . The method of claim 13 , further comprising not flowing the coolant through the coolant lines and not flowing the coolant through each of the EGHX, RAHX, and TSV while an amount of time after the engine shutoff is greater than a threshold amount of time, and not flowing the coolant through the coolant lines and not flowing the coolant through each of the EGHX, RAHX, and TSV while the EGHX fluid outlet temperature is less than a third threshold temperature and the rear axle oil temperature is less than the first threshold temperature.

15 . A method for a rear axle coolant system of an engine, comprising:
during engine operation: responsive to a first condition, recovering exhaust gas heat at an exhaust gas heat exchanger (EGHX) via coolant in a coolant loop and storing the recovered exhaust gas heat in a thermal storage vessel (TSV); responsive to a second condition, transferring heat from the TSV to rear axle lubrication oil via a rear axle heat exchanger (RAHX); and during engine non-operation: responsive to a temperature of the rear axle lubrication oil, adjusting a flow of the coolant to the RAHX; responsive to a temperature of the TSV, adjusting a flow of the coolant to the TSV; and responsive to a temperature of the EGHX, adjusting a flow rate of the coolant through the coolant loop.

16 . The method of claim 15 , wherein the first condition comprises the temperature of the rear axle lubrication oil being above a first threshold temperature, and wherein the second condition comprises the temperature of the rear axle lubrication oil being below the first threshold temperature, while the temperature of the TSV is equal to or greater than the rear axle lubrication oil temperature.

17 . The method of claim 16 , wherein adjusting the flow of the coolant to the RAHX includes actuating a first valve, wherein adjusting the flow of the coolant to the TSV includes actuating a second valve, and wherein adjusting the flow rate of the coolant through the coolant loop includes adjusting a pump rate of a coolant pump fluidly coupled with the coolant loop.

18 . The method of claim 17 , wherein actuating the first valve includes not adjusting an amount of opening of a coolant inlet of the first valve while adjusting an amount of opening of at least one coolant outlet of the first valve, and wherein actuating the second valve includes not adjusting an amount of opening of a coolant inlet of the second valve while adjusting an amount of opening of at least one coolant outlet of the second valve.

19 . The method of claim 18 , wherein during engine non-operation, the coolant is pumped through the coolant pump until the temperature of the rear axle lubrication oil and the temperature of the EGHX are each below a second threshold temperature, with the second threshold temperature based on a boiling temperature of the coolant.

20 . The method of claim 19 , wherein a vehicle including the engine is a hybrid-electric vehicle, and wherein engine non-operation is defined as a condition in which an electric motor of the vehicle is not energized and the vehicle is not in motion.

Assignees

• Ford Global Tech Llc

Inventors

• Bonkoski Phillip
• Bidner David Karl
• Cole W Cary
• Russell Jeremy L
• Rollinger John

Classifications

• F01P2060/16

  Outlet manifold · CPC title

• F28D15/00

  Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls {; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies (F28D17/00, F28D19/00, F28D20/00 take precedence)} · CPC title

• F01P2031/30

  Cooling after the engine is stopped · CPC title

• F01P7/164

  by varying pump speed · CPC title

• F28F2250/08

  Fluid driving means, e.g. pumps, fans · CPC title