US 5,014,573 AGranted

Double transition upshift control in an automatic transmission

AssigneeGeneral Motors Corporation

InventorsJoseph H. Hunter, Jeffrey K. Runde

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Abstract

In an automatic transmission, a double transition upshift to a target range requires the release of two off-going clutches and the engagement of two on-coming clutches. The shift is made in two stages. The first stage involves a first off-going clutch and a first on-coming clutch, and begins a shift to a third range having a speed ratio lower than the target range so that input speed is decreased and power is supplied throughout the shift. The speed decrease is managed by a closed-loop control of the first on-coming clutch until the clutch reaches a synchronous speed for the target range. The closed-loop control parameter is on-coming clutch slip speed which is controlled to a calculated slip speed profile. The profile has a first steep slope and a final less steep slope so that the actual slip can smoothly go to zero in a given time period. When near synchronous speed is reached, the second off-going clutch begins to release and at the end of the closed-loop control the second on-coming clutch is applied to complete the shift to the target range.

Claims10

Dependent claims

In a vehicular automatic transmission having an input and an output, a turbine connected to the input to couple driving torque thereto, in which an upshift from a first transmission speed ratio to a second transmission speed ratio is carried out through concurrent disengagement of first and second off-going fluid pressure operated torque transmitting means associated with the first of such speed ratios and engagement of first and second on-coming fluid pressure operated torque transmitting means associated with the second of such speed ratios, wherein a third speed ratio lower than the second speed ratio is effected when the first on-coming torque transmitting means is engaged while the second off-going torque transmitting means is still engaged, and further having turbine and output speed sensing means, a method of controlling the torque transmitting means to effect an upshifting from the first speed ratio to the second speed ratio comprising the steps of:

beginning a shift to the third speed ratio by releasing the first off-going torque transmitting means and gradually engaging the first on-coming torque transmitting means while the second off-going torque transmitting means is still engaged, so that the turbine speed gradually decreases relative to the output speed,
determining from the turbine speed and the output speed when the relative speeds attain a predetermined relationship, and then
effecting the second ratio by releasing the second off-going torque transmitting means, engaging the second on-coming torque transmitting means and completing the engagement of the first on-coming torque transmitting means.

In a vehicular automatic transmission having an input and an output, a turbine connected to the input to couple driving torque thereto, in which an upshift from a first transmission speed ratio to a second transmission speed ratio is carried out through concurrent disengagement of first and second off-going fluid pressure operated torque transmitting devices associated with the first speed ratio and engagement of first and second on-coming fluid pressure operated torque transmitting devices associated with the second speed ratio, wherein a third speed ratio lower than the second speed ratio is effected when the first on-coming torque transmitting device is engaged while the second off-going torque transmitting device is still engaged, and further having turbine and output speed sensing means, the method of controlling the torque transmitting devices to effect a shifting from the higher speed ratio to the lower speed ratio comprising the steps of:

commanding a progressively decreasing hydraulic pressure on the first off-going torque transmitting device during a pressure relief period,
during the said pressure relief period, commanding supplied pressure to the first on-coming torque transmitting device for a set time and then commanding the supplied pressure to an initial value and increasing the commanded pressure at a rate calibrated to achieve a timely decrease in turbine speed,
when a turbine speed decrease is obtained, removing the pressure from the first off-going torque transmitting device and initiating a closed-loop control period of the first on-coming torque transmitting device,
during the closed-loop control period, controlling the pressure command on the first on-coming torque transmitting device to control the sensed turbine speed according to a predetermined function of speeds,
during the closed-loop period, initiating the removal of pressure from the second off-going torque transmitting device and preparing the second on-coming torque transmitting device to assume torque carrying capacity,
detecting release of the second off-going torque transmitting device,
when release of the second off-going torque transmitting device is detected, gradually increasing the commanded on-coming pressure on the first and second on-coming torque transmitting devices to a maximum value.

4 more elements

Dependencies are inferred from the claim text.