A steering method for an industrial truck. The industrial truck includes a pivot plate which is mounted to be rotatable about a steering axis in two steering directions, three wheels, one of the three wheels being designed as a central wheel which is rotatably mounted about an axis of rotation in the pivot plate, and a hydraulic cylinder which rotates the pivot plate about the steering axis. The method includes exerting steering forces of at least approximately equal magnitude on the pivot plate to provide a rotation about the steering axis in each of the two steering directions.

A hydraulic steering unit (2) includes a steering unit (2) including a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (LR), a steering valve arrangement having two valve elements (32, 33) arranged in a housing (30, 38, 39) and being moveable in relation to each other to change characteristics of orifices, and a measuring motor (9) arranged in a line between the steering valve arrangement and one of the working ports (LR). A hydraulic steering unit should create similar end stop sealings in both steering directions. To this end, backpressure means are provided generating a backpressure on the measuring motor (9), wherein the backpressure means are controlled by the valve element (32, 33), and friction means (43, 43′) are provided between one of the valve elements (33) and the housing (30, 38, 39) or a rotating part of the measuring motor (9) and the housing (30, 38, 39), respectively.

A hydraulic steering unit (2) includes a steering unit (2) including a supply port arrangement having a supply port (P) and a return port (T), a working port arrangement having two working ports (LR), a steering valve arrangement having two valve elements (32, 33) arranged in a housing (30, 38, 39) and being moveable in relation to each other to change characteristics of orifices, and a measuring motor (9) arranged in a line between the steering valve arrangement and one of the working ports (LR). A hydraulic steering unit should create similar end stop sealings in both steering directions. To this end, backpressure means are provided generating a backpressure on the measuring motor (9), wherein the backpressure means are controlled by the valve element (32, 33), and friction means (43, 43′) are provided between one of the valve elements (33) and the housing (30, 38, 39) or a rotating part of the measuring motor (9) and the housing (30, 38, 39), respectively.

The present application provides a full hydraulic synchronous steering system for a low-speed heavy-load vehicle, where the system includes: a steering control mechanism and a steering actuator; by determining a desired steering curve between a steering wheel angle and a rear wheel angle, when a steering error exceeds an allowable error, a controller controls the opening and closing of an oil replenishment solenoid valve (5) and an oil discharge solenoid valve (4) to adjust a flow rate of the oil flowing into a steering cylinder (7), so as to ensure that the steering error is within an allowable error range, thereby implementing synchronous steering. A method for manipulating the full hydraulic synchronous steering system is further provided. The full hydraulic synchronous steering system and the method can improve synchronous steering capability of the low-speed heavy-load vehicle and change a steering ratio, thereby improving safety and direction feeling of a driver.

The present application provides a full hydraulic synchronous steering system for a low-speed heavy-load vehicle, where the system includes: a steering control mechanism and a steering actuator; by determining a desired steering curve between a steering wheel angle and a rear wheel angle, when a steering error exceeds an allowable error, a controller controls the opening and closing of an oil replenishment solenoid valve (5) and an oil discharge solenoid valve (4) to adjust a flow rate of the oil flowing into a steering cylinder (7), so as to ensure that the steering error is within an allowable error range, thereby implementing synchronous steering. A method for manipulating the full hydraulic synchronous steering system is further provided. The full hydraulic synchronous steering system and the method can improve synchronous steering capability of the low-speed heavy-load vehicle and change a steering ratio, thereby improving safety and direction feeling of a driver.

The present disclosure relates to a hydraulic steering device of an agricultural work vehicle comprising a steering pump for supplying a working fluid; an automatic steering unit which uses the working fluid to change the traveling direction of the agricultural work vehicle when automatic steering is performed by a control unit; a manual steering unit which uses the working fluid to change the traveling direction of the agricultural work vehicle when manual steering is performed by operating a steering handle; and an automatic cut-off unit which is for selectively cutting off the supply of the working fluid for the automatic steering to a steering cylinder of the agricultural work vehicle according to whether the manual steering is performed.

A system for hydraulic parallel work systems is provided. The system includes a fixed displacement pump (110), a closed-center circuit (300), an open-center hand metering unit (HMU) (200), and a tank (120). The closed-center circuit is in fluid communication with the fixed displacement pump. The open-center HMU is in fluid communication with the fixed displacement pump at an inlet port (204) of the HMU. The tank is fluidly connected to the inlet port of the HMU when the HMU is inactive.

A system for hydraulic parallel work systems is provided. The system includes a fixed displacement pump (110), a closed-center circuit (300), an open-center hand metering unit (HMU) (200), and a tank (120). The closed-center circuit is in fluid communication with the fixed displacement pump. The open-center HMU is in fluid communication with the fixed displacement pump at an inlet port (204) of the HMU. The tank is fluidly connected to the inlet port of the HMU when the HMU is inactive.

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 (α) and the effective steering angle at the wheels (β). 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.

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 (α) and the effective steering angle at the wheels (β). 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.