A quick response steering system with a steering device that steers a vehicle. An electro-hydraulic steering circuit couples to the steering device. The electro-hydraulic steering circuit includes a load sensing pump that pumps hydraulic fluid to a steering cylinder. The load sensing pump increases or decreases output from the load sensing pump in response to a pressure differential between a first fluid line and a second fluid line. A precharge valve diverts hydraulic fluid from the first fluid line to the second fluid line. A controller couples to the steering device and the precharge valve. The controller opens the precharge valve in response to input from the steering device to change a first pressure of the first fluid line to increase an output of the load sensing pump.

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.

An articulated work vehicle with linked front and rear frames includes a joystick lever, a force imparting component, a speed sensor, and a controller. The joystick lever is configured to change a steering angle of the front frame with respect to the rear frame by operation by an operator. The force imparting component is configured to impart an assist force or a counterforce to operation of the joystick lever by the operator. The speed sensor is configured to sense speed of the work vehicle. The controller is configured to control the force imparting component so as to impart the assist force or the counterforce according to the speed sensed by the speed sensor.

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 (7) of variable orifices 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 (A2R) 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 hydraulic steering unit should not have a self-alignment but a comfortable feeling for the driver. To this end a variable diagonal orifice A11_12 1 a variable diagonal orifice (A11_12) is connected to the main flow path (2) and to the tank flow path (3), wherein the orifices of the bridge arrangement (7) are closed in neutral position and the diagonal orifice (A11_12) is open in neutral position.

A turning system is configured to move a turning shaft to turn a left wheel and a right wheel of a vehicle. The turning shaft is configured to couple the left wheel and the right wheel to each other. A torsion bar is engaged with the turning shaft via a steering gear box. The turning system includes: a turning mechanism including (i) an electric turning mechanism including an electric motor configured to rotate a portion of the torsion bar which is located upstream of the steering gear box and (ii) a hydraulic turning mechanism configured to apply a moving force to the turning shaft in an axial direction, the moving force being produced by a hydraulic pressure; and an electric-motor controller configured to control the electric motor based on a frictional force in the turning mechanism and a road-surface reaction force that acts between (a) a tire on the left wheel and a tire on the right wheel and (b) a road surface.

A turning system is configured to move a turning shaft to turn a left wheel and a right wheel of a vehicle. The turning shaft is configured to couple the left wheel and the right wheel to each other. A torsion bar is engaged with the turning shaft via a steering gear box. The turning system includes: a turning mechanism including (i) an electric turning mechanism including an electric motor configured to rotate a portion of the torsion bar which is located upstream of the steering gear box and (ii) a hydraulic turning mechanism configured to apply a moving force to the turning shaft in an axial direction, the moving force being produced by a hydraulic pressure; and an electric-motor controller configured to control the electric motor based on a frictional force in the turning mechanism and a road-surface reaction force that acts between (a) a tire on the left wheel and a tire on the right wheel and (b) a road surface.

A variable ratio hydraulic steering device with two or more orbit displacers ensures steering with low actuating forces even in the event of a total or partial failure of the oil flow supply. In the event of a total or partial failure of the oil flow supply, the device is capable of switching from one orbit displacer to another, if necessary, independently of the pressure at the inlet connection of the steering device.

A variable ratio hydraulic steering device with two or more orbit displacers ensures steering with low actuating forces even in the event of a total or partial failure of the oil flow supply. In the event of a total or partial failure of the oil flow supply, the device is capable of switching from one orbit displacer to another, if necessary, independently of the pressure at the inlet connection of the steering device.

A control assembly (20) for overcoming a rotational resistance required to activate supplementary steering force associated with conventional power steering systems. The control assembly (20) includes a shaft (26) subject to rotational resistance via a torsion bar (62). A valve assembly (22) has a first hydraulic circuit (76) that is interchangeable from an unassisted condition (36) to an assisted condition (34) for providing supplementary steering force to a steering gear after the rotational resistance of the torsion bar (22) is overcome by rotating the shaft (26). An actuator (38) includes a second hydraulic circuit (86) interchangeable from an unengaged condition (42) to an engaged condition (40) applying circumferential force on the shaft (26) to overcome the rotational resistance of the torsion bar (62) and rotate the shaft (26) from a non-rotated position thereby activating the supplementary force of the first hydraulic circuit (76).