US 7,320,654 B2
Ratio control system for an automatic transmission in a vehicle
Peter Janssen, Maasbracht (Netherlands)
Assigned to ZF Friedrichshafen AG, 88038 Friedrichshafen (Germany)
Filed on Aug. 30, 2004, as Appl. No. 10/930,016.
Claims priority of application No. 103 41 917 (DE), filed on Sep. 11, 2003.
Prior Publication US 2005/0059528 A1, Mar. 17, 2005
Int. Cl. F16H 59/00 (2006.01)
U.S. Cl. 474—28  [474/18] 9 Claims
OG exemplary drawing
 
1. A method for the controlling ratio-change occurrences of an automatic transmission in a motor vehicle, by at least first and second hydraulic pressure branches (3, 9) having different pressures wherein,
placing first and second pressure reducing valves (4, 5) in the first hydraulic pressure branch (3) by which hydraulic users (S1, S2) are supplied with hydraulic pressure, and
installing a pressure regulation valve (6) in the first hydraulic pressure branch (3) having an output port of which is connected with a line of the second hydraulic pressure branch (9), and
by the activation of the pressure regulation valve (6), the pressure in the first hydraulic pressure branch (3) the highest, necessary operational pressure of the hydraulic users (S1, S2, 11) plus an offset pressure;
during certain operational conditions of the motor vehicle, one of the first and second pressure reducing valves (4, 5) for one of positioning devices of the two hydraulic users (S1, S2) of the transmission is fully open, and as well the offset-pressure is reduced to one of a value zero or nearly zero; and
upon removal of the certain operational conditions, the offset-pressure is once again increased and the pressure reducing valve (5) renews a function as a pressure reducing element.