Control method for improving fuel efficiency of hybrid electric vehicle

• US 20090105926A1
• Filed: 12/28/2007
• Published: 04/23/2009
• Est. Priority Date: 10/17/2007
• Status: Active Grant

• Current Assignee: Hyundai Motor Company (Hyundai Motor Group), Kia Motors Corporation (Kia Corp.)
• Original Assignee: Hyundai Motor Company (Hyundai Motor Group), Kia Motors Corporation (Kia Corp.)
• Inventors: Choi, Yong Kak
• Granted Patent: US 7,867,134 B2
• Time in Patent Office: Days
• US Class Current: 701/102
• CPC Class Codes: B60K 6/543 the transmission being a continuously variable transmission
• CPC Class Codes: B60L 2240/486 Operating parameters
• 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 10/101 Infinitely variable gearings
• 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 20/30 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 2540/12 Brake pedal position
• CPC Class Codes: B60W 2540/16 Ratio selector position
• CPC Class Codes: B60W 2710/0616 Position of fuel or air injector
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y10S 903/93 Conjoint control of different elements

Abstract

The present invention provides a control method for a hybrid electric vehicle According to a control method of the present invention, the fuel efficiency is improved by extending a fuel cut operation in a wider transmission range and the impact caused by the extended fuel cut operation is reduced by reaction control of a motor operating in the opposite direction to engine torque.

Claims

1. A control method for improving fuel efficiency of a hybrid electric vehicle comprising the steps of:

(a) having an engine control unit prepare for a fuel cut operation by determining whether the fuel cut operation is available and, at the same time, having a hybrid control unit transmit a fuel cut enabling signal to the engine control unit which has completed the preparation of the fuel cut operation, thereby performing the fuel cut operation;

(b) having the hybrid control unit determine whether a transmission gear ratio reaches a preset value of gear ratio and, if it reaches the preset value of gear ratio, transmit a fuel cut cancellation signal to the engine control unit, thereby cancel the fuel cut operation;

(c) having the engine control unit receiving the fuel cut cancellation signal restart the engine; and

(d) having the hybrid control unit perform a reaction control of a motor operating in the opposite direction to engine torque so that the torque being transmitted to a continuously variable transmission is input smoothly.

2. The control method of claim 1, wherein, in the step (a), if the vehicle is decelerated with a brake pedal not pressed and an air conditioner is turned off, the fuel cut operation continues until a preset gear ratio condition is met.

3. The control method of claim 1, wherein, in the step (a), if the vehicle is decelerated with a brake pedal not pressed and an air conditioner is turned on, the fuel cut operation continues until a preset gear ratio condition is met, and a gear ratio is corrected in view of load of the air conditioner.

4. The control method of claim 1, wherein, in the step (a), if the vehicle is decelerated with a brake pedal pressed and an air conditioner is turned off, the fuel cut operation continues until the vehicle is stopped.

5. The control method of claim 4, wherein if the vehicle is decelerated with a brake pedal pressed and an air conditioner is turned off, engine drag generated when the engine is turned off during vehicle stop is boosted by the motor to perform an idle stop.

6. The control method of claim 1, wherein, in the step (a), if the vehicle is decelerated with a brake pedal pressed and an air conditioner is turned on, the fuel cut operation continues until the vehicle is stopped, and a gear ratio is corrected in view of load of the air conditioner.