Shift inhibit control for multi-mode hybrid drive
AssigneeGeneral Motors Corporation
InventorsJy-Jen F. Sah, Todd M Steinmetz
Life of this patent
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Abstract
An electrically variable transmission has a pair of clutches and a first mode when the first clutch is applied and the second clutch released, a second mode when the second clutch is applied and the first clutch released, and a fixed-ratio mode when both clutches are applied. Upshifts and downshifts out of fixed-ratio are accomplished in accordance with a control based upon shift confidence factors determined in accordance with proportional and derivative input speed error quantities. Shift cycling is avoided by applying a variety of conditional tests intended to inhibit return to fixed-ratio operation.
Claims14
Method for reducing the occurrence of shift cycling subsequent to exiting a two-clutch fixed-ratio mode in an electrically variable transmission including an input member and an output member, first and second clutches and first and second modes, said first mode characterized by simultaneous first clutch application and second clutch release, said second mode characterized by simultaneous first clutch release and second clutch application, said two-clutch fixed-ratio mode characterized by simultaneous first and second clutch applications wherein the transmission input member is mechanically coupled to the transmission output member through a fixed ratio, comprising:
- providing a predetermined desired input member speed;
- determining a synchronous speed for the input member whereat slip across first and second clutches is substantially zero;
- incrementing a shift confidence factor as a function of a) the difference between the desired input member speed and the synchronous speed and b) the difference between the rate of change of the desired input member speed and the rate of change of the synchronous speed;
- and,
- inhibiting the simultaneous application of said first and second clutches until said shift confidence factor attains a predetermined threshold.
Method for controlling an electrically variable transmission while in one of a first and a second mode, said transmission including an input member and an output member, first and second clutches, and first, second and fixed-ratio modes, said first mode characterized by simultaneous first clutch application and second clutch release, said second mode characterized by simultaneous first clutch release and second clutch application, said fixed-ratio mode characterized by simultaneous first and second clutch applications wherein the transmission input member is mechanically coupled to the transmission output member through a predetermined fixed ratio, comprising:
- providing a predetermined desired input member speed;
- determining a synchronous speed for the input member whereat slip across first and second clutches is substantially zero;
- and,
- inhibiting simultaneous application of first and second clutches in accordance with a predetermined relationship among proportional and derivative error quantities determined from said desired input member speed and said synchronous speed.
Method for controlling shifting of an electrically variable transmission out of one of a first and a second mode, said transmission including an input member and an output member, first and second clutches, said first mode characterized by simultaneous first clutch application and second clutch release, said second mode characterized by simultaneous first clutch release and second clutch application, and synchronous operation characterized by substantially zero slip across both first and second clutches, comprising:
- calculating a confidence factor indicative of the desirability of operating in an active one of the first and second modes;
- scheduling shifts out of the active mode;
- and,
- inhibiting shifts out of the active mode as a function of the shift confidence factor.
Dependencies are inferred from the claim text.