Automatic transmission downshifts based on tire adhesion limits
AssigneeGeneral Motors Corporation
InventorJames M. Gessner
Life of this patent
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Abstract
A shift control system that controls gear shifts in a vehicle includes a transmission and a controller. The controller detects driving conditions of the vehicle, estimates a traction load of the vehicle and determines a current traction load of the vehicle. The controller shifts the transmission based on the current traction load and the estimated traction load if the driving conditions are met. The current traction load is based on a lateral acceleration signal and a longitudinal acceleration signal. The estimated traction load is based on a curb weight of the vehicle, a weight transfer gain and an acceleration signal.
Claims20
A shift control system for controlling gear shifts in a vehicle, comprising:
- a transmission;
- a controller that detects driving conditions of said vehicle, that indicates a downshift of said transmission based on said driving conditions, that estimates a traction load of said vehicle, that determines a current traction load of said vehicle, that selectively inhibits said downshift if a square of said current traction load is less than a square of said estimated traction load.
A method of controlling automatic transmission shifts in a vehicle, comprising:
- detecting driving conditions of said vehicle;
- indicating a downshift of a transmission based on said driving conditions;
- estimating a traction load of said vehicle;
- calculating a current traction load of said vehicle;
- and
- selectively inhibiting said downshift if a square of said current traction load is less than a square of said traction load.
A method of controlling automatic transmission downshift of a vehicle, comprising:
- detecting downshift conditions;
- estimating a traction load of said vehicle based on a lateral acceleration signal;
- estimating a current traction load of said vehicle based on a longitudinal acceleration signal;
- and
- selectively inhibiting said downshift if a square of said current traction load is less than a square of said traction load.
Dependencies are inferred from the claim text.