Motor vehicle powertrain control method for low traction conditions

• US 20040259684A1
• Filed: 06/18/2003
• Published: 12/23/2004
• Est. Priority Date: 06/18/2003
• Status: Active Grant

• Current Assignee: GM Global Technology Operations LLC (General Motors Company)
• Original Assignee: GM Global Technology Operations Incorporated (Motors Liquidation Co. GUC Trust)
• Inventors: Hubbard, Gregory A., Kresse, John P., Hitch, Ronald P.
• Granted Patent: US 7,101,313 B2
• Time in Patent Office: Days
• US Class Current: 477/115
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/103 Accelerator thresholds, e.g. kickdown
• CPC Class Codes: B60W 2710/0666 Engine torque
• CPC Class Codes: B60W 2710/105 Output torque
• CPC Class Codes: B60W 30/188 Controlling power parameters of the driveline, e.g. determining the required power

Abstract

A driver-initiated low traction control method limits the drive torque of a motor vehicle during operation on low traction road surfaces. The low traction control mode is initiated by actuation of a switch or by moving a transmission range selector to a Low range while the vehicle is substantially stopped, and terminated by further actuation of the switch or by returning the range selector back to the Drive setting. The low traction control mode limits the engine torque as required to limit the drive wheel torque and its rate of change, so long as cruise control is inactive, the accelerator pedal setting is less than a reference level, and the transmission is operating in a gear other than its top gear. When the low traction control mode is terminated, the engine torque limits are progressively removed in a way that does not produce perceptible acceleration or deceleration of the vehicle.

Claims

1. A control method for a motor vehicle powertrain including an engine driving an automatic shift transmission, the method comprising the steps of:

activating a low traction control mode in response to operator actuation of a control input without regard to wheel slip of said vehicle;

limiting an output torque of said engine during activation of said low traction control mode based on an output speed of said transmission and an operator torque request; and

terminating said low traction control mode in response to operator actuation of said control input during activation of said low traction control mode.

2. The control method of claim 1, where said transmission includes a range selector, and the method includes the steps of:

activating said low traction control mode in response to (1) operator actuation of a control panel switch, or (2) movement of said range selector to a low range setting while said output speed is substantially zero; and

terminating said low traction control mode in response to (1) operator actuation of said control panel switch during activation of said low traction control mode, or (2) movement of said range selector to a normal range setting during activation of said low traction control mode.

3. The control method of claim 1, where said powertrain includes a driver activated cruise control, and the method includes the steps of:

suspending the limitation of engine output torque during activation of said cruise control; and

commencing the limitation of engine output torque upon deactivation of said cruise control.

4. The control method of claim 1, including the step of:

suspending the limitation of engine output torque so long as said driver torque request exceeds a reference value.

5. The control method of claim 1, where said transmission selectively establishes one of a plurality of gear ratios, and the method includes the step of:

suspending the limitation of engine output torque so long as a specified or higher gear ratio of said transmission is established.

6. The control method of claim 1, including the steps of:

determining an effective operator torque request corresponding to the limited engine output torque during activation of said low traction control mode; and

selecting a desired gear ratio of said transmission based on said effective operator torque request.

7. The control method of claim 1, including the steps of:

determining a transmission output torque limit;

determining a first limit on the output torque of said engine based on said transmission output torque limit;

determining a second limit on the output torque of said engine based on said output speed and said operator torque request; and

limiting the output torque of said engine during activation of said low traction control mode based on the lower of said first and second limits.

8. The control method of claim 7, including the step of:

limiting a rate of change of said transmission output torque limit to a calibrated rate of change.

9. The control method of claim 1, including the step of:

limiting a rate of change of said output torque upon termination of said low traction control mode.

10. The control method of claim 1, including the steps of:

determining a first limit on the output torque of said engine based on said output speed and said operator torque request;

determining a second limit on the output torque of said engine during shifting of said transmission; and

limiting the output torque of said engine during activation of said low traction control mode based on the lower of said first and second limits.