Method for controlling idle stop mode in hybrid electric vehicle

• US 7,789,796 B2
• Filed: 11/29/2007
• Issued: 09/07/2010
• Est. Priority Date: 07/13/2007
• 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
• Primary Examiner(s): HO, HA DINH
• Application Number:
  US11/947,032
• Publication Number:
  US 20090017985A1
• Time in Patent Office: 1,013 Days
• Field of Search: 477/2, 477/101, 477/107, 477/110, 477/111
• US Class Current: 477/107
• CPC Class Codes: B60K 6/485 Motor-assist type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60K 6/543 the transmission being a continuously variable transmission
• 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 10/107 with endless flexible members
• 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 2510/1075 fluid pressure, e.g. oil pressure
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 30/18054 at stand still, e.g. engine in idling state hill holding B60W30/18118
• CPC Class Codes: B60W 30/18072 Coasting
• CPC Class Codes: B60W 30/18127 Regenerative braking
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A method for controlling an idle stop mode in a hybrid electric vehicle includes performing an engine RPM lift-up control to raise an engine RPM if a deceleration is less than a medium deceleration when a speed of a hybrid electric vehicle reaches an idle stop mode entering speed such that as the engine RPM is raised, a gear changing oil pressure is increased, so that a continuously variable transmission (CVT) gear ratio according to a deceleration reaches a target minimum gear ratio, and as the CVT gear ratio reaches the target minimum gear ratio, entering an idle stop mode even when a deceleration is less than a medium deceleration while a transmission control unit (TCU) does not perform a control operation for preventing an idle stop mode from being entered.

Claims

1. A method for controlling an idle stop mode in a hybrid electric vehicle, comprising:

performing an engine RPM lift-up control to raise an engine RPM if a deceleration is less than a medium deceleration when a speed of the hybrid electric vehicle reaches an idle stop mode entering speed such that as the engine RPM is raised, a gear changing oil pressure is increased so that a continuously variable transmission (CVT) gear ratio according to the deceleration reaches a target minimum gear ratio; and

as the CVT gear ratio reaches the target minimum gear ratio, entering the idle stop mode even when the deceleration is less than the medium deceleration while a transmission control unit (TCU) does not perform a control operation for preventing the idle stop mode from being entered.

2. The method of claim 1, wherein the step of performing the engine RPM lift-up control to raise the engine RPM comprises:

in a fuel-on state, at the TCU, asking an engine control unit (ECU) to lift up the engine RPM to thereby raise the engine RPM; and

in a fuel-cut state, at the TCU, asking a hybrid control unit (HCU) to lift up the engine RPM, and at the HCU, sending a command signal to a motor control unit (MCU) to drive a motor to thereby raise the engine RPM.

3. The method of claim 1, wherein when the speed of the hybrid electric vehicle reaches the idle stop mode entering speed and if a deceleration is the medium deceleration, a regenerative braking torque scale control according to the deceleration is performed by the HCU, so that regenerative braking torque is sequentially reduced.

4. The method of claim 1, wherein when the speed of the hybrid electric vehicle reaches the idle stop mode entering speed and if a deceleration is a high deceleration, a regenerative braking torque scale control is further performed by the HCU, so that regenerative braking torque becomes zero (0).

5. The method of claim 1, wherein when the speed of the hybrid electric vehicle reaches the idle stop mode entering speed and if a deceleration is an abrupt deceleration, control for preventing the idle stop mode from being entered is performed for safety by the HCU and the TCU.