Systems and methods for controlling an automatic transmission during a flying engine start using a flow accumulator

1. A method for controlling a transmission during a flying engine start, the method comprising:

receiving a request for an internal combustion engine to be started to generate a level of transmission output torque while a vehicle is solely driven by an electric motor-generator, the vehicle including the internal combustion engine, the electric motor-generator, the transmission, and a flow accumulator, the transmission including a first clutch and a second clutch;

determining a gear ratio in the transmission according to the level of transmission output torque;

determining a time lapse between a moment when the first clutch starts to be filled and a moment when the second clutch starts to be filled such that the first clutch and the second clutch reach first and second clutch pressure thresholds, respectively, at substantially the same time;

transferring a transmission fluid from the flow accumulator to the first clutch; and

transferring at least some of the transmission fluid from the flow accumulator to the second clutch after the determined time lapse has passed since the first clutch started to be filled.

2. The method of claim 1 , further comprising determining a transmission fluid temperature, wherein the time lapse is based on the transmission fluid temperature.

3. The method of claim 1 , further comprising determining a volume of the transmission fluid in the flow accumulator, wherein the time lapse is based on the volume of the transmission fluid in the flow accumulator.

4. The method of claim 1 , further comprising determining a pressure of the transmission fluid in the flow accumulator, wherein the time lapse is based on the pressure of the transmission fluid in the flow accumulator.

5. The method of claim 1 , wherein the time lapse is based on volumes of the transmission fluid in the first and second clutches.

6. The method of claim 1 , further comprising determining which of the first and second clutches has to receive the transmission fluid first.

7. The method of claim 6 , wherein the first clutch defines a first volume, the second clutch defines a second volume, and the first volume is larger than the second volume.

8. The method of claim 7 , wherein the transmission fluid in the flow accumulator is only transferred to the first clutch and the second clutch.

9. The method of claim 1 , further comprising determining if a third clutch needs to be filled based on the level of transmission output torque.

10. The method of claim 9 , further comprising determining a time lapse between a moment when the second clutch starts to be filled and a moment when the third clutch starts to be filled such that the first clutch, the second clutch, and the third clutch reach first, second, and third clutch pressure thresholds, respectively, at substantially the same time.

11. A vehicle comprising:

an axle;

an internal combustion engine operatively coupled to the axle;

an electric motor-generator;

a transmission operatively coupled between the engine and the axle, the transmission being configured to transfer torque from the internal combustion engine to the axle, and the transmission including a first clutch and a second clutch;

a flow accumulator containing transmission fluid;

a first valve operatively coupled between the flow accumulator and the first clutch, the first valve being configured to control flow of transmission fluid between the flow accumulator and the first clutch;

a second valve operatively coupled between the flow accumulator and the second clutch, the second valve being configured to control flow of transmission fluid between the flow accumulator and the second clutch; and

a controller in communication with the first and second valves, the controller being configured to:

receive a request for the internal combustion engine to be started to generate a level of transmission output torque while the vehicle is solely driven by the electric motor-generator;

determine a gear ratio in the transmission according to the level of transmission output torque;

determine a time lapse between a moment when the first clutch starts to be filled and a moment when the second clutch starts to be filled such that the first clutch and the second clutch reach first and second clutch pressure thresholds, respectively, at substantially the same time;

send a first clutch command to the first valve such that the first valve allows the transmission fluid to be transferred from the flow accumulator to the first clutch; and

send a second clutch command to the second valve such that the second valve allows at least some of the transmission fluid to be transferred from the flow accumulator to the second clutch after the determined time lapse has passed since the first clutch started to be filled.

12. The vehicle of claim 11 , further comprising a temperature sensor configured to determine a temperature of the transmission fluid, wherein the time lapse is based on the temperature of the transmission fluid.

13. The vehicle of claim 11 , further comprising a volume sensor configured to determine a volume of the transmission fluid in the flow accumulator, wherein the time lapse is based on the volume of the transmission fluid in the flow accumulator.

14. The vehicle of claim 11 , further comprising a pressure sensor configured to determine a pressure of the transmission fluid in the flow accumulator, wherein the time lapse is based on the pressure of the transmission fluid in the flow accumulator.

15. The vehicle of claim 11 , wherein the time lapse is based on volumes of transmission fluid in the first and second clutches.

16. The vehicle of claim 11 , wherein the controller is configured to determine which of the first and second clutches has to receive the transmission fluid from the flow accumulator first.

17. The vehicle of claim 16 , wherein the first clutch defines first volume, the second clutch defines a second volume, and the first volume is larger than the second volume.

18. The vehicle of claim 17 , wherein the transmission fluid in the flow accumulator is only transferred to the first clutch and the second clutch.

19. A system, comprising:

a flow accumulator containing transmission fluid;

a first valve in fluid communication with the flow accumulator, the first valve being configured to control flow of transmission fluid between the flow accumulator and a first clutch;

a second valve in fluid communication with flow accumulator, the second valve being configured to control flow of transmission fluid between the flow accumulator and a second clutch; and

a controller in communication with the first and second valves, the controller being configured to:

receive a request for an internal combustion engine to be started to generate a level of transmission output torque while a vehicle is solely driven by an electric motor-generator, the vehicle including the internal combustion engine, the electric motor-generator, a transmission, and a flow accumulator, the transmission including a first clutch and a second clutch;

determine a gear ratio in the transmission according to the level of transmission output torque;

determine a time lapse between a moment when the first clutch starts to be filled and a moment when the second clutch starts to be filled such that the first clutch and the second clutch reach first and second clutch pressure thresholds, respectively, at substantially the same time;

send a first clutch command to the first valve such that the first valve allows the transmission fluid to be transferred from the flow accumulator to the first clutch; and

send a second clutch command to the second valve such that the second valve allows at least some of the transmission fluid to be transferred from the transmission the flow accumulator to the second clutch after the determined time lapse has passed since the first clutch started to be filled.

20. The system of claim 19 , wherein the controller is configured to determine at least one of a pressure or a volume in the flow accumulator using a model, and the time lapse is based on at least one of the pressure or the volume in the flow accumulator.