US 5,400,678 A · Line pressure optimization in an automatic transmission

Abstract

A method is provided for use in a vehicle including an automatic transmission having at least one load carrying friction element, such as clutch, of optimizing the line pressure in the transmission by slipping the weakest friction element by a small amount. The method includes the steps of decreasing the line pressure from a predetermined base pressure to allow for incipient slip across the weakest friction element and then increasing the line pressure to obtain a temporary pressure at which the weakest friction element is no longer slipping. The method also includes the step of further increasing the line pressure from the temporary pressure to obtain an operating line pressure. Preferably, the operating line pressure provides the weakest friction element with additional capacity for transmitting torque without slip for normal driving conditions, i.e. sensed vehicle throttle positions within a predetermined hysteresis band.

Claims16

Dependent claims

A method, for use in a vehicle having a driveline including an automatic transmission with a plurality of load carrying friction elements, of optimizing a line pressure in the automatic transmission, the method comprising:

(a) decreasing the line pressure from a predetermined base pressure to allow for a small slip within a predetermined range across a weakest load carrying friction element;
(b) increasing the line pressure to obtain a temporary pressure at which the weakest load carrying friction element is no longer slipping;
(c) increasing the line pressure from the temporary pressure to obtain an operating line pressure, the operating line pressure providing the weakest load carrying friction element with additional capacity for transmitting torque without slipping during changes in vehicle throttle position within a predefined hysteresis band having an upper threshold and a lower threshold;
(d) sensing driveline torque transients;
and
(e) repeating steps (a)-(d) during vehicle operation following detection of a transient.

3 more elements

A method, for use in a vehicle including a control unit and an automatic transmission having a plurality of load carrying friction elements, of optimizing a line pressure in the automatic transmission, the method comprising:

(a) sensing a plurality of vehicle operating parameters including vehicle throttle position to obtain associated operating signals;
(b) operating the automatic transmission at a base line pressure, the base line pressure having a value based on the vehicle operating signals;
(c) decreasing the line pressure from the base pressure to allow for a small slip within a predetermined range across a weakest load carrying friction element;
(d) increasing the line pressure to obtain a temporary pressure at which the weakest load carrying friction element is no longer slipping;
(e) increasing the line pressure from the temporary pressure to obtain an operating line pressure, the operating line pressure providing the weakest load carrying friction element with additional capacity for transmitting torque without slipping for sensed throttle position signals within a predefined hysteresis band having an upper threshold and a lower threshold;
(f) increasing the line pressure if the throttle position signal exceeds the upper threshold to a new line pressure at which the weakest load carrying friction element is not slipping;
(g) decreasing the line pressure from the new line pressure to allow for a small slip within a predetermined range across the weakest load carrying friction element;
and
(h) repeating steps (a)-(g) periodically during vehicle operation.

6 more elements

Dependencies are inferred from the claim text.

Line pressure optimization in an automatic transmission

Life of this patent

Line pressure optimization in an automatic transmission

Life of this patent

Abstract

Claims16