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

Patent metadata

Field	Value
Publication number	US-9995385-B2
Application number	US-201213361094-A
Country	US
Kind code	B2
Filing date	Jan 30, 2012
Priority date	Feb 21, 2011
Publication date	Jun 12, 2018
Grant date	Jun 12, 2018

Abstract

A method and device 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.

First claim

The invention claimed is:

1. A device for activating first and second shifting elements (A, B) of an automatic transmission in communication with an automatic start-stop controller that performs an automatic start-stop function, the device comprising:
the automatic transmission in communication with the automatic start-stop controller that performs the automatic start-stop function for automatically starting and stopping an internal combustion engine;
a pump ( 2 ), which supplies the transmission with pressure medium, being driven by the internal combustion engine;
the first and the second shifting elements (A, B) being in a form of one of shifting clutches or shifting brakes, both of the first and the second shifting elements are engaged in a starting gear, and the starting gear being either a first gear or a second gear;
each of the first and the second shifting elements (A, B) being respectively actuatable by an axially movable piston ( 10 or 25 );
each of the pistons ( 10 , 25 ) being acted upon, in an engaging direction, by pressure in a respective actuation pressure space ( 11 or 26 );
at least in a case of the first and the second shifting elements (A, B), each of the pistons being acted upon, in a disengaging direction, by pressure in a respective restoring pressure space ( 14 or 29 ) that acts in opposition to pressure of the respective actuation pressure space ( 11 or 26 ) acting in the engaging direction;
the respective restoring pressure space ( 14 or 29 ) being designed as a controllable restoring force that is selectively rendered inactive when the internal combustion engine is stopped and the supply of the pressure medium is discontinued;
for each of the first and the second shifting elements (A, B), the respective pressures in the actuation pressure spaces and the restoring pressure spaces ( 11 , 14 , 26 , 29 ) act upon the respective pistons in opposition to one another ( 11 , 14 , 26 , 29 ) and the respective pistons each having functional surfaces ( 17 , 18 , 32 , 33 ) with surface areas;
the surface areas of the functional surfaces of the respective piston have a chosen ratio, both of the actuation and the restoring pressure spaces ( 11 , 14 , 26 , 29 ) are pressurized at a same time and at a same pressure such that, based on the chosen ratio, an actuating force for actuating the respective piston of both the first and the second shifting elements (A, B) is applied predominantly in the engaging direction to maintain engagement of the starting gear prior to depressurization of the respective actuation pressure space when the internal combustion engine is stopped by the automatic start-stop function; and
when the automatic start-stop function is active and the internal combustion engine is stopped by the automatic start-stop function, the restoring pressure spaces are depressurized, via a common pressure supply, before depressurization of the actuation pressure spaces to eliminate the restoring force and facilitate maintaining engagement of the first and the second shifting elements and the starting gear, but otherwise both of the restoring pressure spaces ( 14 , 29 ) are continually pressurized to restore the respective piston back into an inactive position during normal driving operation, and the restoring pressure spaces, for restoring the respective pistons, being hydraulically connected to one another and receiving the pressure medium, having a common pressure, from the common pressure supply.

2. The device according to claim 1 , wherein the restoring pressure spaces ( 14 , 29 ) for restoring the pistons are arranged axially opposite the actuation pressure spaces ( 11 , 26 ) that act in the engaging direction for actuating the pistons, the pistons being arranged axially between the restoring pressure spaces ( 14 , 29 ) and the actuation pressure spaces ( 11 , 26 ) that act in the engaging direction.

3. The device according to claim 1 , wherein the restoring pressure spaces ( 14 , 29 ) for restoring the pistons are delimited by the respective pistons ( 10 , 25 ) and pressure-tight diaphragm plates ( 15 , 30 ) that are associated with the pistons ( 10 , 25 ).

4. The device according to claim 1 , wherein a supply-line branching ( 16 , 19 , 31 ), for supplying the pressure-medium to the restoring pressure spaces ( 14 , 29 ) which are hydraulically connected to one another, is located adjacent to the actuation pressure spaces.

5. The device according to claim 1 , wherein each of the restoring pressure spaces ( 14 , 29 ) is devoid of a spring.

6. The device according to claim 1 , wherein during the normal driving operation, the actuation force on the pistons is greater than the restoring force on the pistons ( 10 , 25 ), and the restoring force is supplied by way of the pressure medium supplied to the restoring pressure space ( 14 , 29 ).

7. The device according to claim 1 , wherein the restoring pressure spaces ( 14 , 29 ) for restoring the pistons are arranged on an axial side of the pistons axially opposite the actuation pressure spaces ( 11 , 26 ) that act in the engaging direction for actuating the pistons such that each of the respective restoring pressure spaces ( 14 , 29 ) is located axially between the respective actuation pressure space ( 11 , 26 ) and a respective disk packet ( 5 , 20 ).

8. A device for activating at least two shifting elements of an automatic transmission in communication with an automatic start-stop controller that performs an automatic start-stop function, the device comprising:
the automatic transmission in communication with the automatic start-stop controller that performs the automatic start-stop function for automatically starting and stopping an internal combustion engine;
a pump ( 2 ), for supplying the transmission with pressure medium, being driven by the internal combustion engine;
the at least two shifting elements (A, B) being in a form of one of shifting clutches or shifting brakes, both of the at least two shifting elements being engaged in either a first starting gear or a second starting gear, and each of the at least two shifting elements (A, B) being actuatable by a respective axially movable piston ( 10 , 25 );
each respective piston ( 10 , 25 ) being acted upon, in an engaging direction, by pressure in a respective actuation pressure space ( 11 , 26 );
at least in a case of the shifting elements (A, B), a respective restoring pressure space ( 14 , 29 ) being arranged on an axial side of each of the pistons, opposite the respective actuation pressure space, such that pressure in the restoring pressure space applies a restoring force on the respective piston that acts in opposition to pressure of the actuation pressure space ( 11 , 26 ) which acts in the engaging direction, the restoring pressure spaces are hydraulically connected to each other such that both restoring pressure spaces are pressurizable by the pressure medium at a common pressure at a same time via a common supply line;
each of the restoring pressure spaces ( 14 , 29 ) being controllably pressurizable to apply the restoring force on the respective piston in a disengaging direction, the respective actuation and the restoring pressure spaces ( 11 , 14 , 26 , 29 ) acting in opposition to one another have functional surfaces ( 17 , 18 , 32 , 33 ) with a respective surface area;
a ratio of the surface areas of the functional surfaces is chosen such that, during normal driving operation, the respective actuation and the restoring pressure spaces ( 11 , 14 , 26 , 29 ) acting on the respective pistons in opposition to one another are pressurized at a same pressure at a same time with the internal combustion engine operating, an actuating force for actuating the respective piston

Assignees

• Rogner Horst
• Haupt Josef
• Zahnradfabrik Friedrichshafen

Inventors

• Rogner Horst
• Haupt Josef

Classifications

• F16H61/16

  Inhibiting  {or initiating}  shift during unfavourable conditions  {, e.g. preventing forward-reverse shift at high vehicle speed, preventing engine overspeed}   (F16H61/18 takes precedence) · CPC title

• F16H2063/303

  the friction member is actuated and released by applying pressure to different fluid chambers · CPC title

• Y10T477/688

  Cross-Sectional Technologies · mapped topic

• Y10T477/75

  Cross-Sectional Technologies · mapped topic

• F16H2312/14

  Going to, or coming from standby operation, e.g. for engine start-stop operation at traffic lights · CPC title