Method and device for actuating a shift element of an automatic transmission having a start-stop means

US9194486B2 · kind B2 · utility

Assignee

• ZF FRIEDRICHSHAFEN AG · DE

Inventors

• Horst Rogner · Markdorf, DE
• Josef Haupt · Tettnang, DE

Key dates

• Filing date: Mar 13, 2015
• Grant date: Nov 24, 2015
• Expiry date: Mar 13, 2035

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F16H2312/14
• WIPO field: Mechanical elements
• WIPO sector: Mechanical engineering

Abstract

A method for actuating a shift element of an automatic transmission having a start-stop function and a pressure medium pump driven by an internal combustion engine. The shifting elements are clutches or brakes that can be actuated by a piston which is actuated for engagement via pressure supplied to a pressure space. The pressure space is depressurized when the engine stops. To enhance start-stop operation, the shifting elements comprise an additional pressure space that acts, in opposition to the pressure space acting in the engaging direction, as a controllable restoring mechanism which can be rendered inactive, if desired. If the engine stops and the automatic start-stop function is activated, the additional pressure spaces, acting in the restoring direction, are depressurized before the pressure drop in the pressure spaces, acting in the engaging direction, of the pistons, but are otherwise permanently pressurized during driving operation.