A hydraulic drive device for an industrial vehicle includes a variable displacement pump, a displacement control valve, a power steering cylinder, a power steering valve, a loading cylinder, a loading valve, a hydraulic oil passage, and a pilot line. The displacement control valve controls the variable displacement pump to increase displacement of the variable displacement pump when differential pressure between discharge pressure of hydraulic oil discharged from the variable displacement pump and pilot pressure generated in the pilot line is smaller than a predetermined set pressure. A spool of the loading valve is provided with a groove portion that forms a communication passage that makes communication between the hydraulic oil passage and the pilot line at a neutral position of the loading valve when the power steering valve is located in a neutral position.

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (5) and a tank port (T) connected to a tank flow path (6), a working port arrangement having a left working port (L) connected to a left working flow path (7) and a right working port (R) connected to a right working flow path (8), a bridge arrangement (14) of variable neutral open orifices, said bridge arrangement (14) comprising a first left orifice (A2L) connected to a main flow path (5) and to the left working flow path (7), a first right orifice (A2R) connected to a main flow path (5) and to the right working flow path (8), a second left orifice (A3L) connected to the left working flow path (7) and to the tank flow path (6), and a second right orifice (A3R) connected to the right working flow path (8) and to the tank flow path (6). Such a steering unit has a good steering behavior but can function as a closed-center solution. To this end a further variable orifice arrangement is arranged between the supply port (P) arrangement and the working port arrangement (T), which further orifice arrangement is closed in neutral position.

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (5) and a tank port (T) connected to a tank flow path (6), a working port arrangement having a left working port (L) connected to a left working flow path (7) and a right working port (R) connected to a right working flow path (8), a bridge arrangement (14) of variable neutral open orifices, said bridge arrangement (14) comprising a first left orifice (A2L) connected to a main flow path (5) and to the left working flow path (7), a first right orifice (A2R) connected to a main flow path (5) and to the right working flow path (8), a second left orifice (A3L) connected to the left working flow path (7) and to the tank flow path (6), and a second right orifice (A3R) connected to the right working flow path (8) and to the tank flow path (6). Such a steering unit has a good steering behavior but can function as a closed-center solution. To this end a further variable orifice arrangement is arranged between the supply port (P) arrangement and the working port arrangement (T), which further orifice arrangement is closed in neutral position.

The adjustment assembly of a hydraulic steering system of a vehicle is provided. The adjustment assembly can be positioned between the steering column and the hydraulic steering unit of the system, to adjust the mutual angular position between the rotation angle of the steering column () and the effective steering angle at the wheels ().The adjustment assembly includes an adjustment device including an electric motor and an electronic command unit controlling its actuation; an epicycloidal device including a satellite-carrying member operatively connected to the steering column; at least one satellite gear supported and guided in rotation by the satellite-carrying member; a first solar gear operatively connected to the hydraulic steering unit and to the at least one satellite gear; and a second solar gear operatively connected to the adjustment device and to the first solar gear to control the angular position and/or the rotation of the first solar gear.

A steering system for a work vehicle having a steerable wheel. The steering system includes a steering input device configured to provide a first steering input and a second steering input to move the steerable wheel. A pilot system is operatively connected to the steering input device and includes a first pilot line operatively connected to the first steering input and a second pilot line operatively connected to the second steering input. A piloted system is operatively connected to the pilot system and includes a direction control valve operatively connected to each of the first and second pilot lines and to a steering cylinder. The steering cylinder is coupled to the steerable wheel. The direction control valve responds to each of the pressure signals of the first and second pilot lines to adjust the position of the steering cylinder which in turn moves the steerable wheel.

A steering system for a work vehicle having a steerable wheel. The steering system includes a steering input device configured to provide a first steering input and a second steering input to move the steerable wheel. A pilot system is operatively connected to the steering input device and includes a first pilot line operatively connected to the first steering input and a second pilot line operatively connected to the second steering input. A piloted system is operatively connected to the pilot system and includes a direction control valve operatively connected to each of the first and second pilot lines and to a steering cylinder. The steering cylinder is coupled to the steerable wheel. The direction control valve responds to each of the pressure signals of the first and second pilot lines to adjust the position of the steering cylinder which in turn moves the steerable wheel.

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (2) and a tank port (T) connected to a tank flow path (3), a working port arrangement having a left working port (L) connected to a left working flow path (4) and a right working port (R) connected to a right working flow path (5), a bridge arrangement (21) of variable orifices (A2L, A3L, A2R, A3R) having a first left orifice (A2L) connected to the main flow path (2) and to the left working flow path (4), a first right orifice (A3R) connected to the main flow path (2) and to the right working flow path (5), a second left orifice (A3L) connected to the left working flow path (4) and to the tank flow path (3), and a second right orifice (A3R) connected to the right working flow path (5) and to the tank flow path (3). Such a steering unit allows steering a vehicle with low energy consumption. To this end a load sensing port (LS) is provided, the load sensing port (LS) signaling a pressure in the steering unit (1) to the outside.

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (P) connected to a main flow path (2) and a tank port (T) connected to a tank flow path (3), a working port arrangement having a left working port (L) connected to a left working flow path (4) and a right working port (R) connected to a right working flow path (5), a bridge arrangement (21) of variable orifices (A2L, A3L, A2R, A3R) having a first left orifice (A2L) connected to the main flow path (2) and to the left working flow path (4), a first right orifice (A3R) connected to the main flow path (2) and to the right working flow path (5), a second left orifice (A3L) connected to the left working flow path (4) and to the tank flow path (3), and a second right orifice (A3R) connected to the right working flow path (5) and to the tank flow path (3). Such a steering unit allows steering a vehicle with low energy consumption. To this end a load sensing port (LS) is provided, the load sensing port (LS) signaling a pressure in the steering unit (1) to the outside.

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (8) connected to a main flow path (2) and a tank port (5) connected to a tank flow path (3), a working port arrangement having a left working port (L) connected to a left working flow path (4) and a right working port (R) connected to a right working flow path (5), a variable first left orifice (A2L) connected to the main flow path (2) and to the left working flow path (4), a variable first right orifice (A2R) connected to the main flow path (2) and to the right working flow path (5), a variable second left orifice (A3L) connected to the left working flow path (4) and to the tank flow path (3), and a variable second right orifice (A3R) connected to the right working flow path (5) and to the tank flow path (3). Such a steering unit should allow comfortable steering. To this end a measuring motor (15) is arranged in one of the working flow parts (4, 5).

A hydraulic steering unit (1) is described comprising a supply port arrangement having a pressure port (8) connected to a main flow path (2) and a tank port (5) connected to a tank flow path (3), a working port arrangement having a left working port (L) connected to a left working flow path (4) and a right working port (R) connected to a right working flow path (5), a variable first left orifice (A2L) connected to the main flow path (2) and to the left working flow path (4), a variable first right orifice (A2R) connected to the main flow path (2) and to the right working flow path (5), a variable second left orifice (A3L) connected to the left working flow path (4) and to the tank flow path (3), and a variable second right orifice (A3R) connected to the right working flow path (5) and to the tank flow path (3). Such a steering unit should allow comfortable steering. To this end a measuring motor (15) is arranged in one of the working flow parts (4, 5).