Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2001-01-03
2003-01-14
Schwartz, Christopher P. (Department: 3613)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C180S197000
Reexamination Certificate
active
06506141
ABSTRACT:
TECHNICAL FIELD
The invention relates to an electronically controlled, automatic, multiple-ratio transmission mechanism for a vehicle with traction controls.
BACKGROUND ART
Controls for multiple-ratio transmissions for automotive vehicles include shift scheduling that depends on engine torque and engine speed. Shift control may rely upon a so-called synthetic throttle position determined by a calibrated relationship between engine torque and engine speed for each actual throttle position. The synthetic throttle position information is used to establish line pressure control to achieve the desired capacity for pressure-actuated transmission clutches and brakes, the clutches and brakes being used to control the torque flow paths through the transmission from the engine to the vehicle traction wheels.
If the vehicle has traction control and the vehicle is operating in the traction control mode, the shift point schedule for the normal operating mode will be affected.
A fundamental principle of the control strategy for the traction control mode requires the transmission to assume the highest gear ratio possible without prematurely exiting from the traction control mode to the normal drive mode. The higher the gear ratio, the lower the torque transmitted to the traction wheels.
Traction controls are designed to sense incipient wheel slip. Incipient wheel slip occurs when the computed wheel speed is slightly above the wheel speed corresponding to the normal drive mode for a given vehicle speed. If incipient slip is detected, the traction control system will reduce engine torque by retarding the spark timing or by modifying the rate of fuel delivery to the engine so that the engine torque output is reduced until the wheel slip is below a wheel slip threshold. Exiting from the traction control mode prematurely will cause hunting of the control system in and out of the traction control mode.
In contrast to the operation of the vehicle in the traction control mode, a fundamental performance principle for normal ratio shifts involves a balance between the optimum vehicle powertrain performance and fuel economy. These differences in the fundamental principles for normal powertrain performance and traction control performance, of necessity, require a compromise in the objectives for normal powertrain operation and for traction control operation.
When the vehicle is not in traction control, the input to the shift schedules located in the memory portion of the powertrain controller is the throttle position. When the vehicle is in traction control, a synthetic throttle position is used as the input for determining the vehicle speed at which shifts occur. Synthetic throttle position is obtained by detecting the true engine torque and engine speed and outputting a predicted throttle setting that would be required to generate that true engine torque. The synthetic throttle setting is used as the input for shift scheduling as well as the input to the capacity control for the powertrain controller. throttle setting is used as the input for shift scheduling as well as the input to the capacity control for the powertrain controller.
Because of the fundamental differences in the principles for calibrating shift schedules when traction control is in place are not consistent with the shift schedules desired when the powertrain is in the normal driving mode, a significant change in synthetic throttle position information is necessary to achieve an acceptable traction control shift schedule curve. This includes a change in the relationship of throttle position to engine torque. Of necessity, this produces a mismatch for purposes of capacity control.
DISCLOSURE OF INVENTION
The invention comprises a method for optimizing both shift scheduling and capacity control by calculating a synthetic throttle setting as an input to capacity control. The commanded traction control torque is used as an input to separate shift schedule curves. Thus, there are separate shift curves for operation of the vehicle in traction control and for normal operation while not in traction control. The separate shift schedule curves thus can be calibrated without having the undesirable effect of commanding the incorrect capacity for capacity control purposes. The separate shift schedules allow for shifts to be based on driver input pedal position during operation of the powertrain in the normal mode and for determining the engine torque required for impending wheel slip in the traction control mode.
During a transition from the traction control mode to the normal shifting mode, there is a natural ramped increase in the requested torque. This is detected at the exit of the traction control event. The increase in the desired torque results in an increase in the vehicle speed at which a given shift occurs. That shift is determined by the separate shift schedule that is characteristic of the normal powertrain operating mode without the traction control in place. The appropriate gear for the surface that the vehicle wheels are on is selected at the exit of the traction control event.
REFERENCES:
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patent: 5547435 (1996-08-01), Grutter et al.
patent: 5899830 (1999-05-01), Tabata
patent: 6007454 (1999-12-01), Takahira et al.
patent: 6070118 (2000-05-01), Ohta et al.
Bannon Charles John
Grytzelius Michelle S.
Hartline Barbara Anne
O'Neil Brian Michael
Riedle Bradley Dean
Ford Global Technologies Inc.
McKenzie F. G.
Schwartz Christopher P.
Torres Melanie
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