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Compensated-control-method-for-filling-a-fluid-operated-automatic-transmission-clutch

Compensated control method for filling a fluid-operated automatic transmission clutch

Details

Inventors: Lentz, Carl A.; Long, Charles F.;
Assignee: General Motors Corporation (Detroit, MI)
Primary Examiner: Lall; Parshotam S.
Assistant Examiner: Auchterlonie; Thomas S.
Attorney, Agent or Firm: Navarre; Mark A.

The on-coming clutch of an automatic transmission is filled for a fill time determined from empirical data embodied in look-up tables which relate the effects of pump speed and fluid temperature on the fill time. The fill time is determined for a baseline clutch and then multiplied by a volume ratio for a particular clutch. The effect of fluid temperature on leakage is tabulated and used with the pump speed to determine the effective pumping speed. The effects of fluid temperature on viscosity and oil flow rate are determined and used to adjust the base fill time for low pumping speeds. The fluid retained in a clutch cavity from a recent application and not fully exhausted is also taken into account.

DETAILED DESCRIPTION It is therefore an object of the invention to provide an improved control method for filling an on-coming clutch of an electronically controlled transmission.
It is another object to provide such a control method which takes into account varying pump speed, fluid viscosity, fluid temperature and clutch volume.
According to this invention, the clutch is supplied with fluid for a fill time which is determined as a combined function of a base fill time, the volume ratio of the on-coming clutch, the temperature of the transmission fluid and the time since the on-coming clutch was last exhausted.
The base fill time is determined as a function of the effective pump speed, which in turn, is determined as a function of the measured pump speed, the fluid temperature and an adaptive determined viscosity offset.
The viscosity offset is updated during certain garage shifts, and compensates the effective pump speed for variations in the characteristics of the transmission fluid.

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