Control system for hybrid vehicles

• US 5,862,497 A
• Filed: 03/27/1997
• Issued: 01/19/1999
• Est. Priority Date: 04/10/1996
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Yano, Toru, Tamagawa, Yutaka, Tatara, Yusuke
• Primary Examiner(s): LOUIS JACQUES, JACQUES H
• Application Number:
  US08/829,807
• Time in Patent Office: 663 Days
• Field of Search: 701/22, 701/101, 701/102, 701/103, 701/104, 701/105, 180/65.2, 180/65.3, 180/65.4, 180/65.8, 180/309, 318/139, 318/268, 290/40 C, 290/45
• US Class Current: 701/22
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60K 6/543 the transmission being a continuously variable transmission
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• CPC Class Codes: B60L 15/2054 by controlling transmissions or clutches
• CPC Class Codes: B60L 2240/441 Speed
• CPC Class Codes: B60L 2240/445 Temperature
• 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: 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 10/26 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 20/15 Control strategies specially adapted for achieving a particular effect
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/068 Engine exhaust temperature
• CPC Class Codes: B60W 2510/244 Charge state
• CPC Class Codes: B60W 2530/16 Driving resistance
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2710/0605 Throttle position
• CPC Class Codes: B60W 2710/0616 Position of fuel or air injector
• CPC Class Codes: B60W 2710/0622 : Air-fuel ratio
• CPC Class Codes: F16H 63/40 : comprising signals other than signals for actuating the final output mechanisms
• CPC Class Codes: Y02T 10/40 : Engine management systems
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• 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: Y10S 903/903 : having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/918 : Continuously variable
• CPC Class Codes: Y10S 903/919 : Stepped shift

Abstract

There is provided a control system for a hybrid vehicle including an internal combustion engine, a drive shaft driven by the engine, a motor operable on electrical energy for driving the drive shaft, and electrical storage device for supplying electrical energy to the motor. An amount of assistance of the motor to the engine by driving the drive shaft is calculated based at least on load on the engine. An output from the motor is controlled based on the amount of assistance of the motor to the engine. It is determined whether conditions are satisfied for a lean operating mode of the engine in which an air-fuel ratio of a mixture supplied to the engine is controlled to a leaner value than a stoichiometric value. Changeover of an operating mode of the engine is carried out between a stoichiometric operating mode in which the air-fuel ratio of the mixture supplied to the engine is controlled to a value at or close to the stoichiometric value and the lean operation or the lean operating mode, based on the amount of assistance of the motor to the engine and results of the determination of the lean operating condition.

Claims

1. A control system for a hybrid vehicle including an internal combustion engine, a drive shaft driven by said engine, a motor operable on electrical energy for driving said drive shaft, and electrical storage means for supplying electrical energy to said motor, the control system comprising:

driving assistance amount-calculating means for calculating an amount of assistance of said motor to said engine by driving said drive shaft, based at least on load on said engine;

motor output control means for controlling an output from said motor, based on said amount of assistance of said motor to said engine calculated by said driving assistance amount-calculating means;

lean operating condition-determining means for determining whether conditions are-satisfied for a lean operating mode of said engine in which an air-fuel ratio of a mixture supplied to said engine is controlled to a leaner value than a stoichiometric value; and

air-fuel ratio-changing means for carrying out changeover of an operating mode of said engine between a stoichiometric operating mode in which said air-fuel ratio of said mixture supplied to said engine is controlled to a value at or close to said stoichiometric value and said lean operating mode, based on said amount of assistance of said motor to said engine calculated by said driving assistance amount-calculating means and results of said determination of said lean operating condition-determining means.

2. A control system according to claim 1, including remaining charge-detecting means for detecting an amount of remaining charge in said electrical storage means, and wherein said assistance of said motor to said engine is carried out when said amount of remaining charge in said storage battery means detected by said remaining charge-detecting means is larger than a predetermined lower limit value.

3. A control system according to claim 1, wherein said air-fuel ratio-changing means carries out said changeover of said operating mode of said engine between said stoichiometric operating mode and said lean operating mode by changing a desired air-fuel ratio to which said mixture is to be controlled by air-fuel ratio feedback control, said desired air-fuel ratio being set in dependence on said amount of assistance of said motor to said engine when said engine is in said lean operating mode.

4. A control system according to claim 1, wherein said lean operating condition-determining means includes engine temperature-detecting means for detecting a temperature of said engine, and catalyst temperature-detecting means for detecting a temperature of a catalyst of said engine, said lean operating condition-determining means determining that said conditions for said lean operating mode of said engine are fulfilled when said temperature of said engine detected by said engine temperature-detecting means is higher than a predetermined value and said temperature of said catalyst detected by said catalyst temperature-detecting means is higher than a predetermined value.

5. A control system according to claim 3, wherein said air-fuel ratio-changing means sets said desired air-fuel ratio to a leaner value as said amount of assistance of said motor to said engine is larger.

6. A control system according to claim 2, wherein said motor has a regenerating function of converting kinetic energy of said drive shaft to electrical energy and charging said electrical energy storage means with said electrical energy, said remaining charge-detecting means including cumulative discharged electric power amount-calculating means for calculating a cumulative amount of electric power discharged from said electrical storage means, cumulative charged electric power amount-calculating means for calculating a cumulative amount of electric power supplied to said electrical storage means, and calculating means for calculating said amount of remaining charge in said electrical storage means, based on a difference between said cumulative amount of electric power discharged from said electrical storage means and said cumulative amount of electric power supplied to said electrical storage means.

7. A control system according to claim 1, wherein said engine includes an intake passage, and a throttle valve arranged in said intake passage, said control system including throttle valve opening-detecting means for detecting opening of said throttle valve, said load on said engine being determined from said opening of said throttle valve opening.

8. A control system according to claim 1, wherein said hybrid vehicle includes an accelerator pedal, said control system including accelerator pedal opening-detecting means for detecting opening of said accelerator pedal corresponding to an accelerator pedal travel exerted by a driver of said hybrid vehicle, said load on said engine being determined from said opening of said accelerator pedal.

9. A control system according to claim 7, including engine rotational speed-detecting means for detecting rotational speed of said engine, and wherein said driving assistance amount-calculating means calculates said amount of assistance of said motor to said engine, based on a demanded output of said engine determined based on said load on said engine and said rotational speed of said engine detected by said engine rotational speed-detecting means.

10. A control system according to claim 8, including engine rotational speed-detecting means for detecting rotational speed of said engine, and wherein said driving assistance amount-calculating means calculates said amount of assistance of said motor to said engine, based on a demanded output of said engine determined based on said load on said engine and said rotational speed of said engine detected by said engine rotational speed-detecting means.

11. A control system according to claim 9, wherein said hybrid vehicle includes driving wheels, and a transmission arranged between said driving wheels and said engine and said motor, said control system including gear reduction ratio-detecting means for detecting a parameter representative of a gear reduction ratio of said transmission, and vehicle speed-detecting means for detecting traveling speed of said hybrid vehicle, said driving assistance amount-calculating means calculating an extra output of said engine by subtracting running resistance of said hybrid vehicle calculated based on said traveling speed of said hybrid vehicle from said demanded output of said engine, and for calculating said driving assistance amount, based on said extra output of said engine, said parameter representative of said gear reduction ratio of said transmission detected by said gear reduction ratio-detecting means and said rotational speed of said engine detected by said engine rotational speed-detecting means.

12. A control system according to claim 10, wherein said hybrid vehicle includes driving wheels, and a transmission arranged between said driving wheels and said engine and said motor, said control system including gear reduction ratio-detecting means for detecting a parameter representative of a gear reduction ratio of said transmission, and vehicle speed-detecting means for detecting traveling speed of said hybrid vehicle, said driving assistance amount-calculating means calculating an extra output of said engine by subtracting running resistance of said hybrid vehicle calculated based on said traveling speed of said hybrid vehicle from said demanded output of said engine, and for calculating said driving assistance amount, based on said extra output of said engine, said parameter representative of said gear reduction ratio of said transmission detected by said gear reduction ratio-detecting means and said rotational speed of said engine detected by said engine rotational speed-detecting means.