US 11,988,277 B2
Hydraulic system for a transmission of a motor vehicle
Alexander Haberstock, Ravensburg (DE); and Thilo Schmidt, Meckenbeuren (DE)
Assigned to ZF Friedrichshafen AG, Friedrichshafen (DE)
Filed by ZF Friedrichshafen AG, Friedrichshafen (DE)
Filed on Apr. 7, 2023, as Appl. No. 18/297,287.
Claims priority of application No. 10 2022 203 576.3 (DE), filed on Apr. 8, 2022.
Prior Publication US 2023/0323944 A1, Oct. 12, 2023
Int. Cl. F16H 61/00 (2006.01); F16H 61/02 (2006.01)
CPC F16H 61/0009 (2013.01) [F16H 61/0025 (2013.01); F16H 61/0206 (2013.01); F16H 2061/0253 (2013.01); F16H 61/0267 (2013.01)] 12 Claims
OG exemplary drawing
 
1. A hydraulic system (1; 100; 200) for a transmission (2) of a motor vehicle (3), comprising:
a pump system (5) with a first pressure outlet (6) and a second pressure outlet (7);
a primary circuit (11);
a secondary circuit (12); and
a system pressure valve (8) with a system pressure valve slide (9),
wherein the hydraulic system (1; 100; 200) is configured such that a secondary pump pressure (PPsek) output from the second pressure outlet (7) of the pump system (5) is fed to a radial pressure surface (26; 36) of the system pressure valve slide (9), and therefore an axial load based on the secondary pump pressure (PPsek) acts upon the radial pressure surface (26; 36) of the system pressure valve slide (9) such that the system pressure valve slide (9) is urged counter to a mechanical preload force out of a first switching position into a second switching position,
wherein the system pressure valve slide (9) comprises two adjacent pistons (29, 30) having different diameters (d1, d2),
wherein the pistons (29, 30) are spaced apart from each other in an axial direction (x1) of the system pressure valve slide (9),
wherein the piston (29) with a greater diameter (d1) forms the radial pressure surface (26) of the system pressure valve slide (9), and
wherein the axial load based on the secondary pump pressure (PPsek) acts upon the radial pressure surface (26) of the piston (29) with the greater diameter (d1) such that the system pressure valve slide (9) is urged counter to the mechanical preload force out of the first switching position into the second switching position.