US 6,319,172 B1 · Off-going clutch control for upshifting of an automatic transmission

Abstract

An improved transmission upshift control in which the off-going clutch is controlled to emulate the behavior of an ideal free-wheel device to thereby achieve nearly ideal timing of the off-going clutch disengagement relative to the on-coming clutch engagement. During the preparation phase of the shift, the off-going pressure is reduced in proportion to the estimated volume of fluid supplied to the on-coming clutch such that the off-going pressure is at a calibrated value when the on-coming clutch is filled. However, the calibrated value is adjusted upward in direct relation to the transmission input torque above a given level so as to emulate the reaction torque that would be exerted by an ideal free-wheel device for maintaining the current speed ratio. The torque phase of the control commences when the estimated volume indicates that the on-coming clutch is completely filled. At such point, the off-going clutch pressure decreases from the calibrated value at a rate determined as a function of the scheduled on-coming clutch torque to emulate the rate of decay that would occur with an ideal free-wheel device as the on-coming clutch engages. If the confidence level is low, the off-going clutch control parameters are biased to extend the engagement of the off-going clutch. If the extended engagement of the off-going clutch results in a tie-up condition due to engagement of the on-coming clutch, the off-going pressure is quickly released.

Claims12

Dependent claims

An off-going clutch control method for an automatic transmission in which shifting from a current speed ratio to a new speed ratio is carried out by supplying hydraulic fluid to an on-coming clutch associated with the new speed ratio to fill and then engage such on-coming clutch in accordance with a commanded torque capacity, and releasing a fluid pressure present in an off-going clutch associated with the current speed ratio to disengage such off-going clutch, the control method comprising the steps of:

determining a cumulative volume of hydraulic fluid supplied to the on-coming clutch;
reducing a fluid pressure in the off-going clutch in relation to the determined cumulative volume of fluid supplied to the on-coming clutch such that the fluid pressure in the off-going clutch reaches a calibrated initial pressure value when the on-coming clutch becomes filled with hydraulic fluid;
and
once the on-coming clutch becomes filled with hydraulic fluid, reducing the fluid pressure in the off-going clutch from said calibrated initial pressure value at a calibrated final release rate determined as a function of the commanded torque capacity of the on-coming clutch, such that the off-going clutch is disengaged at a rate that matches a rate of engagement of the on-coming clutch.

1 more element

determining a cumulative volume of hydraulic fluid supplied to the on-coming clutch;
determining a remaining un-filled volume of the on-coming clutch according to a difference between the determined cumulative volume and a reference volume corresponding to a known volume of said on-coming clutch;
determining a pressure reduction value based on the determined remaining un-filled volume and a desired reduction rate;
controlling the fluid pressure in the off-going clutch according to a sum of a calibrated initial pressure value and the determined pressure reduction value such that the fluid pressure in the off-going clutch reaches said calibrated initial pressure value when the determined remaining un-filled volume reaches zero;
and
when the determined remaining un-filled volume reaches zero, reducing the fluid pressure in the off-going clutch from said calibrated value at a calibrated final release rate determined as a function of the commanded torque capacity of the on-coming clutch such that the off-going clutch is disengaged at a rate that matches a rate of engagement of the on-coming clutch.

3 more elements

Dependencies are inferred from the claim text.

Off-going clutch control for upshifting of an automatic transmission

Life of this patent

Off-going clutch control for upshifting of an automatic transmission

Life of this patent

Abstract

Claims12