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Method-of-controlling-frictionally-engageable-couplings-of-an-automatic-transmission-of-a-motor-vehicle

Method of controlling frictionally engageable couplings of an automatic transmission of a motor vehicle

Details

Inventors: Eschrich, Gerhard; Schreiber, Achim; Schwab, Manfred;
Assignee: Robert Bosch GmbH (Stuttgart, DE)
Primary Examiner: Gruber; Felix D.
Assistant Examiner:
Attorney, Agent or Firm: Frishauf, Holtz, Goodman & Woodward

Reference values are stored for various conditions of gear shift operations of a vehicle motor of a particular type and model for various motor speed and load combinations, the reference values having a magnitude characterizing the gear shifting operation, for example the time interval required from the appearance of a gear shift command until the end of slip in a coupling indicates that the gear shift is complete. As the vehicle is driven, actual values of this magnitude are stored and averaged for a predetermined number of shift operations under the same class of condition. Correction values for the pressure of hydraulic fluid of the gear shift control, originally set at zero for all conditions, are determined by comparison of reference values with average actual values and stored. In subsequent driving, the stored correction values are used to control the pressure of the hydraulic medium to maintain a standard of comfort for all shift operations and new average actual values are used from time to time to modify the correction values for compensation of aging effects.

DETAILED DESCRIPTION It is an object of the present invention to provide an electrically controllable transmission in which shifting from one gear to another can be made to take place without causing riding discomfort, by means that do not require close manufacturing tolerances for the gear chain or the transmission control, and do not involve deterioration as a result of aging effects.
Briefly, frictional engagement elements are used for gear shifting and an actual frictional engagement measure is compared with a stored reference value.
Correction values are stored for use when more than a certain difference is found in the compressors.
The correction value has an effect that corrects a control magnitude for the frictional coupling in the sense of adaptive control.
In electrohydraulic actuation the control magnitude which is corrected, is the hydraulic pressure.
Actual measured magnitude in the operation can be either the duration of the engagement operation or of the slip between frictional elements in a frictionally engageable coupling, or else the gradient of the transmission input shaft speed during the slipping of the frictional elements.
The gradient of the transmission input shaft speed during slip between frictional elements is a magnitude dependent on that duration of slip.
The same is true of the interval between the appearance of a gear shift order and the end of the slip duration interval.
The method of the invention has the advantage that random variations between transmissions and vehicles of the same model and year, and also aging effects, can be compensated to produce a quality of gear shifting that is essentially uniform, by continuous adaptive adjustment of the shift-producing interval.
In consequence, greater tolerances can be permitted for the necessary positioning members and other such components, leading to overall economy of the transmission.
Since the parameter variation and changes which produce the problem here in question involve no high frequency disturbances, but only very low frequency drifts for long term deviations away from desired values, adaptive control is particularly well suited to deal with the problem

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