초록 ▼

A system and method for managing a power source in a vehicle having an engine and an electric machine includes setting first and second discharge limits for the power source, where the second discharge limit is higher than the first discharge limit. A buffer value is determined as a function of at l

A system and method for managing a power source in a vehicle having an engine and an electric machine includes setting first and second discharge limits for the power source, where the second discharge limit is higher than the first discharge limit. A buffer value is determined as a function of at least the second discharge limit and an engine-on power requirement. A driver demand for power is determined, and the engine is started when the engine is off and the driver demand for power exceeds the buffer value.

대표청구항 ▼

What is claimed: 1. A method for managing a power source in a vehicle including an engine and an electric machine, each of the engine and the electric machine being operable to output torque to at least one vehicle wheel, the engine having an engine-on power requirement for starting the engine, the

What is claimed: 1. A method for managing a power source in a vehicle including an engine and an electric machine, each of the engine and the electric machine being operable to output torque to at least one vehicle wheel, the engine having an engine-on power requirement for starting the engine, the power source being operable to supply power to the electric machine and having a first operating temperature range, a second operating temperature range above the first operating temperature range, and a third operating temperature range below the first operating temperature range, the method comprising: setting a first discharge limit for the power source that is substantially constant over the first operating temperature range and decreasing over the second and third operating temperature ranges, the first discharge limit being at least partly based on an amount of power that is supplied by the power source for a first predetermined period of time; setting a second discharge limit for the power source higher than the first discharge limit the second discharge limit being at least partly based on the temperature of the power source and an amount of power that is supplied by the power source for a second predetermined amount of time that is less than the first predetermined amount of time, and which is based on an amount of time required to start the engine; determining a buffer value as a function of at least the second discharge limit and the engine-on power requirement; determining a driver demand for power; and starting the engine when the engine is off and the driver demand for power exceeds the buffer value. 2. The method of claim 1, further comprising inhibiting engine shutdown when the engine is on and the driver demand for power exceeds the buffer value. 3. The method of claim 1, wherein the first discharge limit decreases as a temperature of the power source increases over a predetermined temperature range, the method further comprising limiting torque output of the electric machine when at least one predetermined condition is met, including the driver demand for power being less than the first discharge limit and the temperature of the power source being within the predetermined temperature range. 4. The method of claim 3, the vehicle further including an accelerator pedal, wherein the at least one predetermined condition includes the accelerator pedal being depressed by at least a predetermined amount. 5. The method of claim 1, further comprising allowing the engine to be shut down when the driver demand for power is less than the buffer value. 6. The method of claim 1, wherein the at least one condition of the power source includes a usage factor, the usage factor being applied to increase the first and second discharge limits over a respective temperature range of the power source. 7. The method of claim 1, further comprising inhibiting use of the electric machine when the driver demand for power exceeds the second discharge limit. 8. A method for managing a power source in a vehicle including an engine and an electric machine, the engine being operable to output torque to at least one vehicle wheel and having an engine-on power requirement for starting the engine, the electric machine being operable to output torque to at least one vehicle wheel, and further operable to provide torque to start the engine, the power source being operable to supply power to the electric machine and having a first operating temperature range, a second operating temperature range above the first operating temperature range, and a third operating temperature range below the first operating temperature range, the method comprising: setting a first discharge limit for the power source as a function of at least one power source condition, including a temperature of the power source and at least partly based on an amount of power than is supplied by the power source for a first predetermined period of time, the first discharge limit being substantially constant over the first operating temperature range and decreasing over the second and third operating temperature ranges; setting a second discharge limit for the power source as a function of at least one power source condition, including the temperature of the power source, the second discharge limit being higher than the first discharge limit and at least partly based on the engine-on power requirement, and an amount of power that is supplied by the power source for a second predetermined amount of time that is less than the first predetermined amount of time, and which is based on an amount of time required to start the engine; determining a buffer value as a function of at least the second discharge limit and the engine-on power requirement; determining a driver demand for power; determining a temperature of the power source; and starting the engine when the engine is off and the driver demand for power exceeds a respective buffer value for the determined power source temperature. 9. The method of claim 8, further comprising limiting the torque output of the electric machine when certain conditions are met, including the driver demand being less than the first discharge limit and the determined temperature of the power source being within the second or third operating temperature range. 10. The method of claim 9, the vehicle further including an accelerator pedal operable by the driver to indicate the driver power demand, wherein the certain conditions further include the accelerator pedal being depressed by at least a predetermined amount. 11. The method of claim 10, wherein the torque output of the electric machine is limited according to a function of at least the determined temperature of the power source and a position of the accelerator pedal. 12. The method of claim 8, further comprising inhibiting engine shutdown when the engine is on and the driver demand for power exceeds a respective buffer value for the determined power source temperature. 13. The method of claim 8, further comprising allowing the engine to be shut down when the driver demand for power is less than a respective buffer value for the determined power source temperature. 14. The method of claim 8, further comprising: determining a usage factor based on power source usage; and applying the usage factor to the discharge limits to increase the discharge limits.