Hybrid vehicles

• US 7,455,134 B2
• Filed: 05/08/2006
• Issued: 11/25/2008
• Est. Priority Date: 09/14/1998
• Status: Expired due to Fees

• Current Assignee: Abell Foundation Incorporated
• Original Assignee: Paice LLC
• Inventors: Louckes, Theodore, Severinsky, Alex J.
• Primary Examiner(s): Ellis; Christopher
• Assistant Examiner(s): COLLADO, CYNTHIA FRANCISCA
• Application Number:
  US11/429,457
• Publication Number:
  US 20060231305A1
• Time in Patent Office: 932 Days
• Field of Search: 180/65.2, 180/65.4, 180/205, 180/65.1, 180/65.8, 180/65.7, 180/701, 701/54
• US Class Current: 180/65.28
• CPC Class Codes: B60H 1/004 for vehicles having a combustion engine and electric drive means, e.g. hybrid electric vehicles
• CPC Class Codes: B60H 1/3222 characterised by the compressor driving arrangements, e.g. clutches, transmissions or multiple drives B60H1/3208, B60H1/3226 take precedence
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 2006/268 Electric drive motor starts the engine, i.e. used as starter motor
• CPC Class Codes: B60K 6/22 characterised by apparatus, components or means specially adapted for HEVs
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/442 Series-parallel switching type
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 2200/26 Rail vehicles
• CPC Class Codes: B60L 2210/20 AC to AC converters
• CPC Class Codes: B60L 2220/12 Induction machines
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2220/16 DC brushless machines
• CPC Class Codes: B60L 2240/34 Cabin temperature
• CPC Class Codes: B60L 2240/36 Temperature of vehicle components or parts
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/443 : Torque
• CPC Class Codes: B60L 2240/445 : Temperature
• CPC Class Codes: B60L 2260/28 : Four wheel or all wheel drive
• CPC Class Codes: B60L 2270/145 : Structure borne vibrations
• CPC Class Codes: B60L 50/16 : with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/61 : by batteries charged by engine-driven generators, e.g. series hybrid electric vehicles
• CPC Class Codes: B60L 53/00 : Methods of charging batteries, specially adapted for electric vehicles; Charging stations or on-board charging equipment therefor; Exchange of energy storage elements in electric vehicles
• CPC Class Codes: B60L 53/20 : characterised by converters located in the vehicle
• CPC Class Codes: B60L 58/10 : for monitoring or controlling batteries
• CPC Class Codes: B60L 58/12 : responding to state of charge [SoC]
• CPC Class Codes: B60L 7/18 : Controlling the braking effect B60L7/12, B60L7/14, B60L7/16 take precedence
• CPC Class Codes: B60L 7/26 : Controlling the braking effect
• CPC Class Codes: B60T 11/18 : Connection thereof to initiating means
• CPC Class Codes: B60T 13/586 : the retarders being of the electric type
• CPC Class Codes: B60T 2270/60 : Regenerative braking
• CPC Class Codes: B60T 2270/604 : Merging friction therewith; Adjusting their repartition
• CPC Class Codes: B60T 7/06 : Disposition of pedal
• CPC Class Codes: B60T 8/17 : Using electrical or electronic regulation means to control braking detecting or indicating faulty operation B60T8/885
• CPC Class Codes: B60T 8/172 : Determining control parameters used in the regulation, e.g. by calculations involving measured or detected parameters B60T8/17551 takes precedence
• 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 10/18 : including control of braking systems
• 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 20/10 : Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 20/14 : in conjunction with braking regeneration
• CPC Class Codes: B60W 20/15 : Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 20/30 : Control strategies involving selection of transmission gear ratio control of change speed gearings, together with other vehicle sub-units B60W10/10; HEV transmission gearing B60K6/36; gearings and control thereof F16H
• CPC Class Codes: B60W 2510/0633 : Turbocharger state
• CPC Class Codes: B60W 2510/0657 : Engine torque
• CPC Class Codes: B60W 2510/244 : Charge state
• CPC Class Codes: B60W 2530/16 : Driving resistance
• CPC Class Codes: B60W 2540/12 : Brake pedal position
• CPC Class Codes: B60W 2710/08 : Electric propulsion units
• CPC Class Codes: B60W 2710/18 : Braking system
• CPC Class Codes: B60W 2710/244 : Charge state
• CPC Class Codes: B60W 30/18127 : Regenerative braking
• CPC Class Codes: B60Y 2200/91 : Electric vehicles
• CPC Class Codes: B60Y 2200/92 : Hybrid vehicles
• CPC Class Codes: B60Y 2300/18125 : Regenerative braking
• CPC Class Codes: B60Y 2300/91 : Battery charging
• CPC Class Codes: B60Y 2400/112 : Batteries
• CPC Class Codes: B60Y 2400/435 : Supercharger or turbochargers
• CPC Class Codes: B60Y 2400/81 : Braking systems
• CPC Class Codes: F01N 3/2013 : using electric or magnetic heating means
• CPC Class Codes: F02B 37/00 : Engines characterised by provision of pumps driven at least for part of the time by exhaust
• CPC Class Codes: F02B 37/16 : by bypassing charging air
• CPC Class Codes: F02B 37/18 : by bypassing exhaust from the inlet to the outlet of turbine or to the atmosphere
• CPC Class Codes: F02D 2250/18 : Control of the engine output torque
• CPC Class Codes: F02D 41/0007 : for control of turbo-charged or super-charged engines control of the pumps per se F02B37/12
• CPC Class Codes: F02M 35/10157 : Supercharged engines
• CPC Class Codes: F02M 35/10163 : having air intakes specially adapted to selectively deliver naturally aspirated fluid or supercharged fluid
• CPC Class Codes: F02N 11/0818 : Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode
• CPC Class Codes: F02N 2200/061 : Battery state of charge [SOC]
• CPC Class Codes: H01M 10/4207 : for several batteries or cells simultaneously or sequentially
• CPC Class Codes: H01M 2220/20 : Batteries in motive systems, e.g. vehicle, ship, plane
• CPC Class Codes: Y02A 50/20 : Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02T 10/12 : Improving ICE efficiencies
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• 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
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 90/14 : Plug-in electric vehicles
• CPC Class Codes: Y10S 903/903 : having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/904 : Component specially adapted for hev
• CPC Class Codes: Y10S 903/907 : Electricity storage, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/93 : Conjoint control of different elements
• CPC Class Codes: Y10S 903/946 : Characterized by control of driveline clutch
• CPC Class Codes: Y10S 903/947 : Characterized by control of braking, e.g. blending of regeneration, friction braking

Abstract

A hybrid vehicle comprises an internal combustion engine, a traction motor, a starter motor, and a battery bank, all controlled by a microprocessor in accordance with the vehicle'"'"'s instantaneous torque demands so that the engine is run only under conditions of high efficiency, typically only when the load is at least equal to 30% of the engine'"'"'s maximum torque output. In some embodiments, a turbocharger may be provided, activated only when the load exceeds the engine'"'"'s maximum torque output for an extended period; a two-speed transmission may further be provided, to further broaden the vehicle'"'"'s load range. A hybrid brake system provides regenerative braking, with mechanical braking available in the event the battery bank is fully charged, in emergencies, or at rest; a control mechanism is provided to control the brake system to provide linear brake feel under varying circumstances.

Claims

1. A hybrid vehicle, comprising:

at least two wheels, operable to receive power to propel said hybrid vehicle;

a first alternating current (AC) electric motor, operable to provide power to said at least two wheels to propel said hybrid vehicle;

a second AC electric motor;

an engine coupled to said second electric motor, operable to provide power to said at least two wheels to propel the hybrid vehicle, and/or to said second electric motor to drive the second electric motor to generate electric power;

a first alternating current-direct current (AC-DC) converter having an AC side coupled to said first electric motor, operable to accept AC or DC current and convert the current to DC or AC current respectively;

a second AC-DC converter coupled to said second electric motor, at least operable to accept AC current and convert the current to DC;

an electrical storage device coupled to a DC side of said AC-DC converters, wherein the electrical storage device is operable to store DC energy received from said AC-DC converters and provide DC energy to at least said first AC-DC converter for providing power to at least said first electric motor; and

a controller, operable to start and stop the engine to minimize fuel consumption;

wherein a ratio of maximum DC voltage on the DC side of at least said first AC-DC converter coupled to said first electric motor to current supplied from said electrical storage device to at least said first AC-DC converter, when maximum current is so supplied, is at least 2.5.

2. The hybrid vehicle of claim 1, wherein both said AC-DC converters are capable of converting DC provided by said electrical storage device to AC, and wherein said maximum current is measured on one or more respective DC sides thereof.

3. The hybrid vehicle of claim 1, wherein said ratio is more than 2.5 during supply of maximum power from said electrical storage device to at least said two wheels by said first electric motor.

4. The hybrid vehicle of claim 1, wherein said ratio is at least 3.

5. The hybrid vehicle of claim 1, wherein the maximum DC voltage is at least approximately 500 volts.

6. The hybrid vehicle of claim 1, wherein the maximum current is less than approximately 150 amperes.

7. The hybrid vehicle of claim 1, wherein said controller is further operable to:

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation.

8. The hybrid vehicle of claim 7, wherein said controller is operable to stop said engine when said vehicle load on said engine results in torque lower than 30% of the MTO of the engine.

9. The hybrid vehicle of claim 7, wherein said controller is operable to start and operate said engine when said vehicle load is sufficient to require said engine to produce torque at least equal to a setpoint (SP), and wherein said SP is substantially less than the MTO of said engine.

10. The hybrid vehicle of claim 9, wherein said SP is at least 20% of the MTO of the engine.

11. The hybrid vehicle of claim 9, wherein said SP is at least 30% of the MTO of the engine.

12. The hybrid vehicle of claim 9, wherein said controller is operable to disable engine operation when the vehicle load results in torque below a second setpoint (SP2), wherein said SP2 is less than said SP.

13. The hybrid vehicle of claim 9, wherein said second electric motor is sized so as to be able to accept said engine torque equal to at least said SP.

14. The hybrid vehicle of claim 9, wherein said SP varies over said engine speed range.

15. The hybrid vehicle of claim 9, wherein the controller is operable to start and operate the engine at torque output levels less than SP under abnormal and transient conditions to satisfy drivability and/or safety considerations.

16. The hybrid vehicle of claim 1, wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque.

17. The hybrid vehicle of claim 16, wherein said threshold value is no more than about 2% per revolution.

18. The hybrid vehicle of claim 16, wherein said controller is operable to vary said threshold value with respect to a state of charge of said electrical storage device.

19. The hybrid vehicle of claim 1, wherein a maximum torque on at least said two wheels produced by said first electric motor or both electric motors is larger than a maximum torque on at least said two wheels produced by said engine.

20. The hybrid vehicle of claim 1, wherein a maximum rotational speed of said first electric motor is at least 50% larger than a maximum rotational speed of said engine.

21. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first AC electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and said third AC electric motor coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle.

22. The hybrid vehicle of claim 21, wherein relative amounts of power directed to said first and second pairs of wheels by the first and third electric motors, respectively, is controlled by said controller.

23. The hybrid vehicle of claim 21, wherein a torque range-broadening transmission is interposed between said engine and said at least said two wheels to which said engine is operable to provide power.

24. The hybrid vehicle of claim 21, wherein a maximum torque provided to said first and second pairs of two wheels by said first and third electric motors, or by said first and third electric motors and said second electric motor, is larger than a maximum torque on at least said two wheels produced by said engine.

25. The hybrid vehicle of claim 21, wherein a maximum rotational speed of said first electric motor is at least 50% larger than a maximum rotational speed of said engine.

26. The hybrid vehicle of claim 1, wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

27. The hybrid vehicle of claim 1, wherein said engine is preheated prior to starting.

28. The hybrid vehicle of claim 1, wherein said controller is further operable to:

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation, and

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of the vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque.

29. The hybrid vehicle of claim 1, wherein said controller is further operable to:

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation;

wherein said hybrid vehicle further comprises a third AC electric motor; and

wherein said first AC electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and said third AC electric motor is is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle.

30. The hybrid vehicle of claim 1, wherein said controller is further operable to:

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation;

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

31. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first AC electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and said third AC electric motor is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle, and

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second and/or third motors to supply additional power to at least said two wheels to supply remaining required torque.

32. The hybrid vehicle of claim 1,

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second and/or third motors to supply additional power to at least said two wheels to remaining required torque;

and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

33. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first alternating current (AC) electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and a said third AC electric motor is provided and is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle; and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

34. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first alternating current (AC) electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and a said third AC electric motor is provided and is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle; and

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque; and

wherein said controller is further operable to;

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when the vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation.

35. The hybrid vehicle of claim 1,

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque;

wherein said controller is further operable to;

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when the vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation; and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

36. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first alternating current (AC) electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and a said third AC electric motor is provided and is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle;

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque; and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

37. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first alternating current (AC) electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and a said third AC electric motor is provided and is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle;

wherein said controller is further operable to;

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation; and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

38. The hybrid vehicle of claim 1, further comprising:

a third AC electric motor;

wherein said first alternating current (AC) electric motor is coupled to a first pair of wheels to provide power to said first pair of wheels to propel said hybrid vehicle, and a said third AC electric motor is provided and is coupled to a second pair of wheels to provide power to said second pair of wheels to propel said hybrid vehicle;

wherein said controller is further operable to;

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation;

wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of the vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque; and

wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said turbocharger is so operated when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

39. The hybrid vehicle of claim 1, wherein said controller is further operable to:

start and stop said engine at any speed of said hybrid vehicle;

disable engine operation when road load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enable engine operation at any required combination of its speed and its torque, except said condition of disabling operation.

40. The hybrid vehicle of claim 1, wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of road load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque.

41. A method of control of a hybrid vehicle, said hybrid vehicle comprising:

at least two wheels, operable to receive power to propel said hybrid vehicle;

a first alternating current (AC) electric motor, operable to provide power to said at least two wheels to propel said hybrid vehicle;

a second AC electric motor;

an engine coupled to said second electric motor, operable to provide power to said at least two wheels to propel the hybrid vehicle, and/or to said second electric motor to drive the second electric motor to generate electric power;

a first alternating current-direct current (AC-DC) converter having an AC side coupled to said first electric motor, operable to accept AC or DC current and convert the current to DC or AC current respectively;

a second AC-DC converter coupled to said second electric motor, at least operable to accept AC current and convert the current to DC;

an electrical storage device coupled to a DC side of said AC-DC converters, wherein the electrical storage device is operable to store DC energy received from said AC-DC converters and provide DC energy to at least said first AC-DC converter for providing power to at least said first electric motor; and

a controller, operable to start and stop the engine to minimize fuel consumption;

said method comprising the step of controlling flow of DC current such that a ratio of maximum DC voltage on the DC side of at least said first AC-DC converter coupled to said first electric motor to current supplied from said electrical storage device to at least said first AC-DC converter, when maximum current is so supplied, is at least 2.5.

42. The method of claim 41, wherein said ratio is more than 2.5 during supply of maximum power from said electrical storage device to at least said two wheels by said first electric motor.

43. The method of claim 41, wherein the maximum DC voltage is at least approximately 500 volts.

44. The method of claim 41, wherein the maximum current is less than approximately 150 amperes.

45. The method of claim 41, wherein said controller performs the following additional steps:

starts and stops said engine at any speed of said hybrid vehicle;

disables engine operation when vehicle load on said engine results in torque less than 20% of a maximum torque output (MTO) of said engine; and

enables engine operation at any required combination of its speed and its torque, except said condition of disabling operation.

46. The method of claim 45, wherein said controller stops said engine when said vehicle load on said engine results in torque lower than 30% of the MTO of the engine.

47. The method of claim 45, wherein said controller starts and operates said engine when said vehicle load is sufficient to require said engine to produce torque at least equal to a setpoint (SP), and wherein said SP is substantially less than the MTO of said engine.

48. The method of claim 47, wherein said SP is at least 20% of the MTO of the engine.

49. The method of claim 47, wherein said SP is at least 30% of the MTO of the engine.

50. The method of claim 47, wherein said controller disables engine operation when the vehicle load results in torque below a second setpoint (SP2), wherein said SP2 is less than said SP.

51. The method of claim 47, wherein said SP varies over said engine speed range.

52. The method of claim 47, wherein the controller is operable to start and operate the engine at torque output levels less than SP under abnormal and transient conditions to satisfy drivability and/or safety considerations.

53. The method of claim 41, wherein a rate of change of torque output of said engine is limited to a threshold value, wherein when a rate of change of vehicle load exceeds said threshold value of the rate of change of torque output of the engine, said controller is operable to operate said first motor and/or said second motor to supply additional power to at least said two wheels to supply remaining required torque.

54. The method of claim 53, wherein said threshold value is no more than about 2% per revolution.

55. The method of claim 53, wherein said controller is operable to vary said threshold value with respect to a state of charge of said electrical storage device.

56. The method of claim 41, wherein said engine comprises a turbocharger operable to increase the maximum torque output by said engine, and wherein said method comprises the further step of operating said turbocharger when the power required of said engine exceeds a predetermined value for at least a predetermined period of time.

57. The method of claim 41, comprising the further step of preheating said engine prior to starting.

58. A method for controlling a hybrid vehicle, comprising:

operating a first alternating current (AC) electric motor comprised in the hybrid vehicle to propel the hybrid vehicle, comprising;

providing direct current (DC) from an electrical storage device to a DC side of a first alternating current-direct current (AC-DC) converter;

the first AC-DC converter converting the DC current to AC current;

providing the AC current to the first AC electric motor to drive the AC electric motor; and

providing power to at least two wheels of the hybrid vehicle;

starting and operating an engine comprised in the hybrid vehicle to propel the vehicle and/or drive a second AC electric motor comprised in the hybrid vehicle to generate electric power, comprising providing power to the at least two wheels and/or the second AC electric motor respectively;

converting the generated electric power from AC to DC using a second AC-DC converter; and

storing the converted electric power in the electrical storage device, wherein the electrical storage device is coupled to a DC side of the second AC-DC converter;

wherein a ratio of maximum DC voltage on the DC side of at least said first AC-DC converter coupled to the first electric motor to current supplied from the electrical storage device to at least the first AC-DC converter, when maximum current is so supplied, is at least 2.5.

59. The method of claim 58, further comprising:

disabling engine operation when vehicle load on the engine results in torque less than 20% of a maximum torque output (MTO) of the engine;

wherein said starting and operating the engine comprises starting and operating the engine at any required combination of its speed and its torque, except when the vehicle load on the engine results in torque less than 20% of the MTO of the engine;

wherein said disabling and said starting and operating occurs independently of speed of the hybrid vehicle.

60. The method of claim 58, further comprising:

limiting a rate of change of torque output of the engine to a threshold value; and

operating the first and/or the second AC electric motors to supply additional power to the at least two wheels to supply remaining required torque when a rate of change of vehicle load exceeds the threshold value of the rate of change of torque output of the engine.

61. The method of claim 58, further comprising:

operating a third AC electric motor to provide power to the at least two wheels of the hybrid vehicle to propel the hybrid vehicle;

wherein said providing power to the at least to wheels comprised in said operating the first AC electric motor comprises providing power to a first pair of wheels of the at least two wheels, and wherein said operating the third AC electric motor comprises providing power to a second pair of wheels of the at least to wheels.

62. The method of claim 58, further comprising:

operating a turbocharger comprised by the engine of the hybrid vehicle to increase maximum torque output (MTO) produced by the engine when torque required of the engine exceeds a predetermined value for at least a predetermined period of time.