Patent ID: 7178334

Claim:
Hydrostatic vehicle drive system ( 1 ) comprising at least one first and one second hydraulic pump ( 2 , 3 ) and at least one first and one second hydraulic motor ( 7 , 12 ), wherein the hydraulic pumps ( 2 , 3 ) and the hydraulic motors ( 7 , 12 ) are coupled together in differential lock mode such that a first connection ( 14 ) of the first hydraulic pump ( 2 ) is connected to a first connection ( 8 ) of the first hydraulic motor ( 7 ), a second connection ( 6 ) of the first hydraulic motor ( 7 ) is connected to a first connection ( 10 ) of the second hydraulic pump ( 3 ), a second connection ( 9 ) of the second hydraulic pump ( 3 ) is connected to a first connection ( 13 ) of the second hydraulic motor ( 12 ), and a second connection ( 11 ) of the second hydraulic motor ( 12 ) is connected to a second connection ( 5 ) of the first hydraulic pump ( 2 ), the first hydraulic motor ( 7 ) and the second hydraulic motor ( 12 ) each having an absorption volume which is adjustable by a respective adjusting device ( 20 , 21 ), including a synchronizing mechanism ( 68 , 64 , 65 , 56 , 57 ) which synchronizes the adjustment provided by the adjusting devices ( 20 , 21 ) of the hydraulic motors ( 7 , 12 ), at least one actuating pressure regulation system ( 56 , 48 ; 57 , 49 ) which increases the absorption volume of the associated hydraulic motor ( 12 ; 7 ) when there is a rise in the pressure in a working circuit ( 16 – 19 ) connecting the hydraulic pumps ( 2 , 3 ) to the hydraulic motors ( 7 , 12 ) upstream of a therewith associated hydraulic motor ( 20 , 21 ), the actuating pressure regulation system ( 56 , 48 ; 57 , 49 ) comprising a servo valve ( 56 , 57 ) which is connected upstream of each adjusting device ( 20 , 21 ) and a control line ( 76 , 77 ) which is connected to a working circuit section ( 18 , 19 ; 16 , 17 ) carrying the higher pressure of the working circuit ( 16 – 19 ) which connects the associated hydraulic motor ( 7 ; 12 ) to the hydraulic pumps ( 2 , 3 ), and wherein each servo valve ( 56 , 57 ) is connected via an electrically operable direction of rotation-changeover valve ( 48 , 49 ) to the sections ( 18 , 19 ; 16 , 17 ) of the working circuit ( 16 – 19 ) which are connected to the associated hydraulic motor ( 7 , 12 ).