Hybrid vehicle driven by composit torque generated by an internal-combustion engine and an electric motor, and method of operating same

• US 6,570,265 B1
• Filed: 02/09/2000
• Issued: 05/27/2003
• Est. Priority Date: 04/28/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Shiraishi, Takuya, Sukegawa, Yoshihiro, Nogi, Toshiharu, Oosuga, Minoru
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): GONZALEZ, JULIO CESAR
• Application Number:
  US09/485,398
• Time in Patent Office: 1,203 Days
• Field of Search: 290/40.C, 290/45, 180/65.2, 123/295, 123/430, 701/102
• US Class Current: 290/40.00C
• CPC Class Codes: B60K 6/26 characterised by the motors or the generators
• CPC Class Codes: B60K 6/442 Series-parallel switching type
• CPC Class Codes: B60K 6/46 Series type
• CPC Class Codes: B60L 50/15 with additional electric power supply with capacitors charged by engine-driven generators B60L50/40; with batteries charged by engine-driven generators B60L50/61
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60W 10/04 including control of propulsion units
• 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 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0622 Air-fuel ratio
• CPC Class Codes: F01N 5/04 the devices using kinetic energy
• CPC Class Codes: F02B 1/12 with compression ignition with fuel-air charge ignited by compression ignition of an additional fuel F02B7/00
• CPC Class Codes: F02D 41/3029 further comprising a homogeneous charge spark-ignited mode
• CPC Class Codes: F02D 41/3035 a mode being the premixed charge compression-ignition mode
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y10S 903/906 : Motor or generator
• CPC Class Codes: Y10S 903/947 : Characterized by control of braking, e.g. blending of regeneration, friction braking

Abstract

A hybrid vehicle driving system has a transmission means (22) for selectively transmitting the output torque of an internal-combustion engine (10), the output torque of an electric motor (19) or a composite torque produced by combining the respective output torques of the internal-combustion engine (10) and the electric motor (19) to driving wheels. The hybrid vehicle driving system includes a turbogenerator (7) capable of converting energy of the exhaust gas discharged from the internal-combustion engine (10) into electric energy, and an electrical connecting means (1) for electrically connecting the turbogenerator (7) to the electric motor (19). The hybrid vehicle driving system is controlled so that the engine (10) operates on a lean mixture for the largest possible part of the total operating time of the engine (10).

Claims

1. A hybrid vehicle driving system comprising:

an internal-combustion engine capable of selectively operating in a first operating mode in which a fuel mixture having an air-fuel ratio not lower than a first predetermined value is supplied to the internal-combustion engine, and a second operating mode in which a fuel mixture having an air-fuel ratio not higher than a second predetermined value, which is smaller than the first predetermined value is supplied to the internal-combustion engine;

an electric motor; and

a transmission for producing a composite torque by combining an output torque of the internal-combustion engine and an output torque of the electric motor and transmitting the composite torque to driving wheels;

wherein the electric motor produces a torque that is applied to reduce the size of step increases or decreases in the output torque of the internal-combustion engine which occurs when the internal-combustion engine changes between the first operating mode and the second operating mode.

2. A hybrid vehicle driving method comprising:

operating an internal-combustion engine selectively in a first operating mode in which a mixture of an air-fuel ratio not lower than a first predetermined value is supplied to the internal-combustion engine, and a second operating mode in which a mixture of an air-fuel ratio not higher than a second predetermined value, which is smaller than the first predetermined value is supplied to the internal combustion engine;

combining respective output torques of the internal-combustion engine and an electric motor to generate a composite torque; and

applying the combined torque to drive wheels of said vehicle;

wherein the electric motor is driven and the air-fuel ratio of the mixture supplied to the internal-combustion engine is maintained at the first value when the air-fuel ratio decreases below the first value while the internal-combustion engine is operating in the first operating mode.

3. The hybrid vehicle driving method according to claim 2, further comprising:

estimating a second air-fuel ratio engine torque that would be produced by the internal-combustion engine when a fuel mixture having the second air-fuel ratio is supplied thereto;

calculating a torque difference between an engine torque produced by the internal-combustion engine when a fuel mixture having the first air-fuel ratio is supplied thereto and the estimated second air-fuel ratio engine torque; and

changing the operating mode of the internal-combustion engine from the first operating mode to the second operating mode when an output torque of the electric motor becomes approximately equal to the calculated torque difference.

4. The hybrid vehicle driving method according to claim 2, further comprising:

estimating a second air-fuel ratio engine torque produced by the internal-combustion engine when it is supplied with a mixture having the second air-fuel ratio; and

changing the operating mode of the internal-combustion engine from the first operating mode to the second operating mode when the sum of an engine torque produced by the internal-combustion engine when a mixture of the first air-fuel ratio is supplied thereto and an output torque of the electric motor exceeds the estimated second air-fuel ratio engine torque.

5. The hybrid vehicle driving method according to claim 4, further comprising:

estimating the second air-fuel ratio engine torque, based on a driving torque variation that occurs when the operating mode of the internal-combustion engine changes from the first operating mode to the second operating mode.