Methods of operating a series hybrid vehicle

• US 7,857,082 B2
• Filed: 02/14/2005
• Issued: 12/28/2010
• Est. Priority Date: 09/25/2003
• Status: Expired due to Fees

• Current Assignee: United States Environmental Protection Agency
• Original Assignee: United States Environmental Protection Agency
• Inventors: Gray, Charles L. Jr.
• Primary Examiner(s): VANAMAN, FRANK BENNETT
• Application Number:
  US11/058,690
• Publication Number:
  US 20050145426A1
• Time in Patent Office: 2,143 Days
• Field of Search: 180/65.1, 180/65.2, 180/65.3, 180/65.4, 180/65.21, 180/65.22, 180/65.245, 180/65.28, 180/65.31, 903/925, 903/943
• US Class Current: 180/65.28
• 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 in a manner that responds to an operator'"'"'s demand for power output, while maximizing engine efficiency and minimizing disruptions in vehicle drivability, may include determining, when the operator makes a demand for power output, whether the secondary power source(s) is supplied with secondary energy stored in an energy storage device(s), direct input energy generated by an engine(s), or both, based on an amount of available secondary energy stored in a secondary storage device(s) alone, or in combination with vehicle speed. While the engine is generating secondary energy, the power efficiency level at which the engine operates may depend on the amount of available stored secondary energy alone, or in combination with vehicle speed. Further, when the engine is not generating secondary energy, the engine may be selectively turned off or idled in response to various operating conditions.

Claims

1. A method of operating a series hybrid vehicle having a primary power source and a secondary power source, the method comprising:

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

operating an engine at one of a plurality of preselected power levels to generate an amount of primary power from the primary power source when the amount of available stored energy is below a first level, the plurality of preselected power levels including a predefined minimum power level for efficient operation of the engine;

converting the amount of primary power from the primary power source into an amount of direct input energy while powering the secondary power source directly with a portion of the amount of direct input energy;

only ever using secondary energy to drive the wheels of the vehicle;

selecting the one of the plurality of preselected power levels based on the amount of available stored energy; and

operating the engine at or near the predefined minimum power level when the amount of available stored energy is within a predetermined range of available stored energy.

2. The method according to claim 1, further comprising:

turning the engine off when the amount of available stored energy is above the first selected level.

3. The method according to claim 1, further comprising:

idling the engine when the amount of available stored energy is above the first selected level.

4. The method according to claim 1, further comprising:

idling the engine when the amount of available stored energy is above the first selected level; and

turning the engine off when the amount of available stored energy is above the first selected level and a command to decelerate the vehicle is issued.

5. The method according to claim 1 wherein the plurality of preselected power levels includes a predefined maximum power level for efficient operation of the engine, and the engine is operated at or near the predefined maximum power level when the amount of available stored energy is within a predetermined range of available stored energy.

6. The method according to claim 5 wherein the predetermined range of available stored energy comprises a range at or near complete depletion of the available stored energy.

7. The method according to claim 1 wherein a number of the plurality of preselected power levels reside within a predefined range of power levels for efficient operation of the engine, and the one of the plurality of preselected power levels is within the predefined range of power levels when the amount of available stored energy is within a predetermined range of available stored energy.

8. The method according to claim 7 wherein the one of the plurality of preselected power levels correlates directionally to an amount of power demanded by a driver of the vehicle.

9. The method according to claim 7 wherein the one of the plurality of preselected power levels is about inversely proportional to the amount of available stored energy within the predetermined range.

10. The method according to claim 1 wherein the engine comprises a first and a second engine, the first selected level of available stored energy is higher than each of a second and a third selected level of available stored energy, and the second selected level is higher than the third selected level, the method further comprising:

operating the first engine when the amount of available stored energy is below the first selected level; and

operating the second engine when the amount of available stored energy is either

     1) below the second selected level and a command to power the vehicle exceeds a predetermined level of power demand, or

     2) when the amount of available stored energy is below the third selected level.

11. The method according to claim 10 wherein, when the second engine is operated, the one of the plurality of preselected power levels for the first engine is at or near a predefined maximum power level for efficient operation of the first engine and the one of the plurality of preselected power levels for the second engine is at or near one of 1) a power level within a predefined range of power levels that is inversely proportional to the amount of available stored energy within a predetermined range of available stored energy and 2) a predefined maximum power level for efficient operation of the second engine.

12. The method according to claim 1 wherein the primary power source comprises a variable displacement engine, the variable displacement engine having a first number of cylinders defining a first engine and a second number of cylinders defining a second engine.

13. The method according to claim 1 wherein the primary power source is either 1) an internal combustion engine, or 2) a Stirling engine.

14. The method according to claim 1, further comprising:

based on the amount of available stored energy, selectively powering the secondary power source with either

     1) a portion of the amount of available stored energy,

     2) the portion of the amount of direct input energy, or

     3) a combination of the portion of the amount of available stored energy and the portion of the amount of direct input energy.

15. The method according to claim 14, further comprising:

powering the secondary power source with the portion of the amount of available stored energy, instead of the portion of the amount of direct input energy, when the available stored energy is above the first selected level.

16. The method according to claim 14, further comprising:

powering the secondary power source with the portion of the amount of direct input energy, instead of the portion of the amount of available stored energy, when the available stored energy is either

     1) below the first selected level and the amount of direct input energy is sufficient to meet a power demand, or

     2) when the available stored energy is below a second selected level.

17. The method according to claim 14, further comprising:

powering the secondary power source with the combination of the portion of the amount of available stored energy and the portion of the amount of direct input energy when the available stored energy is either

     1) below the first selected level and above a second selected level, and the amount of direct input energy is not sufficient to meet a power demand, or

     2) when the amount of available stored energy is above the second selected level.

18. The method according to claim 1 wherein the primary power source can provide at least 60% of the desired peak acceleration power level for the vehicle.

19. The method according to claim 18 wherein the energy storage device can efficiently sustain a charge rate matching at least 20% of the primary power source'"'"'s maximum rated horsepower.

20. The method according to claim 1 wherein the secondary power source is either 1) an electric motor, or 2) a hydraulic motor.

21. The method of claim 1, further comprising:

operating the engine at idle, if the engine is running while the amount of available stored energy is above the first selected level, until the amount of available stored energy falls below the first selected level or until a command to decelerate the vehicle is issued; and

turning the engine off when the amount of available stored energy is above the first selected level and a command to decelerate the vehicle is issued.

22. The method of claim 1 wherein:

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

the step of selecting the one of the plurality of preselected power levels includes selecting, when the amount of available stored energy is below the first selected level and above a second selected level of available stored energy, one of the plurality of power levels according to an inverse relationship between the range of power levels and the amount of available stored energy, such that if the amount of available stored energy is about equal to the first selected level, the selected power level is a lowest one of the plurality of preselected power levels, and if the amount of available stored energy is about equal to the second selected level, the selected power level is a highest one of the plurality of preselected power levels.

23. The method of claim 1 wherein the selecting step comprises selecting the one of the plurality of preselected power levels based solely on the amount of available stored energy.

24. A method of operating a series hybrid vehicle having a primary power source and a secondary power source, the method comprising:

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

operating an engine at one of a plurality of preselected power levels to generate an amount of primary power from the primary power source when the amount of available stored energy is below a first level;

converting the amount of primary power from the primary power source into an amount of direct input energy;

powering the secondary power source directly with a portion of the amount of direct input energy;

using only secondary energy to drive the wheels of the vehicle;

selecting the one of the plurality of preselected power levels based on the amount of available stored energy;

storing, in the energy storage device, a balance of the amount of direct input energy not used to directly power the secondary power source if the amount of direct input energy is greater than the portion of the amount of direct input energy; and

drawing, from the energy storage device, a portion of the amount of available stored energy equal to a difference between the amount of direct input energy and an amount of energy sufficient to meet a power demand if the amount of direct input energy is not sufficient to meet the power demand.