METHODS OF OPERATING A SERIES HYBRID VEHICLE

• US 20110071716A1
• Filed: 11/29/2010
• Published: 03/24/2011
• Est. Priority Date: 09/25/2003
• Status: Active Grant

• Current Assignee: United States Department Of Health And Human Services
• Original Assignee: United States Department Of Health And Human Services
• Inventors: Gray, Charles L. JR.
• Granted Patent: US 8,381,851 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 5/08 comprising more than one engine
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 50/61 by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/13 in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors

Abstract

A method for operating a series hybrid vehicle is provided, in which an engine generates secondary power that is either stored or used as direct input energy by a secondary power source to provide motive power to the vehicle. Regenerative braking is used to convert kinetic energy of the vehicle into secondary energy, which is also stored. When the vehicle driver makes a power demand, the secondary power source is powered by secondary energy from an energy storage device, direct input energy generated by the engine, or both, depending on the amount of stored secondary energy in combination with vehicle speed. When in use, the power level at which the engine is operated is also determined on the basis of available stored energy and vehicle speed. At higher vehicle speeds, the amount of stored energy is allowed to be depleted in order to increase the available storage capacity for regenerative braking.

Claims

1. A method of powering a secondary power source in a series hybrid vehicle, the method comprising:

monitoring an amount of available stored secondary energy within an energy storage device;

monitoring vehicle speed; and

based on the amount of available stored energy at a given vehicle speed, selectively powering the secondary power source with either a portion of the amount of available stored energy or a portion of an amount of direct input energy, or with a combination of the portion of the amount of available stored energy and the portion of the amount of direct input energy.

2. The method of claim 1 wherein selectively powering the secondary power source comprises:

powering the secondary power source only with available stored secondary energy when the amount of available stored energy is above a first selected threshold; and

reducing the first selected threshold as vehicle speed increases.

3. The method of claim 1 wherein selectively powering the secondary power source comprises varying a desired minimum available secondary energy storage capacity in direct relation to a change in vehicle speed.

4. The method of claim 1, comprising:

operating an engine at a first selected power level when the amount of available stored secondary energy is within an upper range;

operating the engine at a second selected power level when the amount of available stored energy is within a lower range;

operating the engine at one of a range of selected power levels when the amount of available stored energy is within a middle range; and

varying one or more of a plurality of thresholds that define the upper, the middle, and the lower ranges of available stored energy at least in part based on vehicle speed.

5. The method of claim 4 wherein the first selected power level is a predefined minimum power level for efficient operation of the engine, the second selected power level is a predefined maximum power level for efficient operation of the engine, and the power levels of the range of selected power levels are respective predefined power levels for efficient operation of the engine, each of which is greater than the first selected power level and lower than the second selected power level.

6. The method of claim 4 wherein each of the first selected power level, the second selected power level, and the power levels of the range of selected power levels is a respective preselected power level comprising a preselected engine speed and a preselected torque value.

7. The method of claim 4 wherein varying the one or more of the plurality of thresholds that define the upper, the middle, and the lower ranges of available stored secondary energy comprises varying the one or more thresholds in inverse relation to changes in vehicle speed while vehicle speed is below a selected value, and varying the one or more thresholds in direct relation to changes in vehicle speed while vehicle speed is above the selected value.

8. A method of operating a series hybrid vehicle, comprising:

using only secondary energy to provide motive power to the vehicle;

operating an engine to generate secondary energy when an amount of available stored secondary energy is below a first selected threshold;

monitoring vehicle speed; and

selecting a value of the first selected threshold based on vehicle speed.

9. The method of claim 8 wherein selecting the value of the first selected threshold comprises varying the value of the first selected threshold in inverse relation to changes in vehicle speed.

10. The method of claim 8, comprising controlling an amount of the secondary energy drawn from the available stored secondary energy to provide motive power to the vehicle, as compared to an amount of the secondary energy provided as direct input energy generated by the engine, on the basis of the amount of available stored secondary energy at a given vehicle speed.

11. The method of claim 10 wherein controlling the amount comprises controlling the amount of available stored secondary energy used, relative to direct input energy, to increase as vehicle speed increases, up to a speed threshold, and to decrease as vehicle speed increases beyond the speed threshold.

12. The method of claim 8, comprising controlling a power level at which the engine is operated based on the amount of available stored secondary energy.

13. The method of claim 12 wherein controlling the power level comprises selecting the power level based on the amount of available stored secondary energy at a given vehicle speed.

14. The method of claim 13 wherein controlling the power level comprises operating the engine at one of a plurality of preselected power levels, and selecting the one of the plurality of preselected power levels according to an inverse relationship with the amount of available stored secondary energy.

15. The method of claim 14 wherein each of the plurality of preselected power levels comprises a preselected engine speed and a preselected torque.

16. The method of claim 14 wherein each of the plurality of preselected power levels lies on a preselected torque/curve line of the engine.

17. The method of claim 14 wherein:

each of the plurality of preselected power levels lies within a predefined range for efficient operation of the engine;

the plurality of preselected power levels includes a predefined minimum power level for efficient operation of the engine;

the plurality of preselected power levels includes a predefined maximum power level for efficient operation of the engine; and

the plurality of preselected power levels includes a range of predefined power levels for efficient operation of the engine that lie between the predefined minimum power level and the predefined maximum power level.

18. The method of claim 17 wherein controlling the power level comprises:

operating the engine at the predefined minimum power level when the amount of available stored secondary energy is below the first selected threshold and above a second selected threshold;

operating the engine at a power level within the range of predefined power levels when the amount of available stored secondary energy is below the second selected threshold and above a third selected threshold; and

operating the engine at the predefined maximum power level when the amount of available stored secondary energy is below the third selected threshold;

the method further comprising selecting values of the second and the third selected thresholds based on vehicle speed.

19. The method of claim 18 wherein selecting the values of the second and the third selected thresholds comprises decreasing the respective values of the second and third thresholds as vehicle speed increases while vehicle speed is below a speed threshold, and increasing the respective values of the second and third thresholds as vehicle speed increases while vehicle speed is above the speed threshold.