A pressure relief valve for a fluid power assist steering system. The valve includes a housing and a spool disposed in the housing. The spool defines a cavity and has a first end and a second end. The spool is movable in the housing to limit an output pressure of the pump. A poppet seat is secured to the second end of the spool. A poppet is disposed in the cavity. A poppet spring biases the poppet into engagement with the poppet seat. A set screw is received in the first end of the spool. The set screw is rotatable relative to the spool to adjust a compression level of the poppet spring.

A pressure relief valve for a fluid power assist steering system. The valve includes a housing and a spool disposed in the housing. The spool defines a cavity and has a first end and a second end. The spool is movable in the housing to limit an output pressure of the pump. A poppet seat is secured to the second end of the spool. A poppet is disposed in the cavity. A poppet spring biases the poppet into engagement with the poppet seat. A set screw is received in the first end of the spool. The set screw is rotatable relative to the spool to adjust a compression level of the poppet spring.

A work vehicle includes a wheel supporting member 11 that is supported by a vehicle body frame 1 that includes left and right side members 80; left and right steerable wheels that are supported by the wheel supporting member 11 so as to be steerable; and a steering mechanism 25 that includes a power steering unit 24 and steers the left and right steerable wheels. The power steering unit 24 is located near the wheel supporting member 11 such that at least a portion of the power steering unit 24 is located between the left and right side members 80.

A work vehicle includes a wheel supporting member 11 that is supported by a vehicle body frame 1 that includes left and right side members 80; left and right steerable wheels that are supported by the wheel supporting member 11 so as to be steerable; and a steering mechanism 25 that includes a power steering unit 24 and steers the left and right steerable wheels. The power steering unit 24 is located near the wheel supporting member 11 such that at least a portion of the power steering unit 24 is located between the left and right side members 80.

A power steering system includes a steering column assembly, a steering gear assembly, and a pressure sensor, and a torque sensor. The steering column assembly has a steering shaft and the steering gear assembly is operatively connected to the steering shaft. The steering gear assembly has an input shaft that extends through a valve housing and extends into a rack housing. The pressure sensor is arranged to provide a pressure signal indicative of a fluid pressure of at least one of a first cavity and a second cavity disposed within the rack housing.

A power steering system includes a steering column assembly, a steering gear assembly, and a pressure sensor, and a torque sensor. The steering column assembly has a steering shaft and the steering gear assembly is operatively connected to the steering shaft. The steering gear assembly has an input shaft that extends through a valve housing and extends into a rack housing. The pressure sensor is arranged to provide a pressure signal indicative of a fluid pressure of at least one of a first cavity and a second cavity disposed within the rack housing.

This invention is a steering system for a trailing or leading axle of a vehicle including a steering angle sensor, a driving speed sensor, an electric motor that drives a hydraulic pump, a working cylinder for steering wheels of the axle, which is joined to the hydraulic pump, a control device which determines a trailing angle of the wheels and which controls the electric motor, wherein the working cylinder has a center position borehole via which hydraulic fluid is emitted, and a piston seals the center position borehole in the straight position of the wheels, wherein the working cylinder is connected to return valves, via which hydraulic fluid can flow back into a tank, wherein the center position borehole is connected to a center position valve, via which hydraulic fluid can flow back into a tank, and wherein the return valves and the center position valve are poppet valves.

A pressure relief valve for a fluid power assist steering system. The valve includes a housing and a spool disposed in the housing. The spool defines a cavity and has a first end and a second end. The spool is movable in the housing to limit an output pressure of the pump. A poppet seat is secured to the second end of the spool. A poppet is disposed in the cavity. A poppet spring biases the poppet into engagement with the poppet seat. A set screw is received in the first end of the spool. The set screw is rotatable relative to the spool to adjust a compression level of the poppet spring.

A steering gear includes a housing defining a chamber. A piston divides the chamber into first and second chamber portions. The piston is moveable along a linear axis relative to the housing upon pressurization of fluid in one of the first and second chamber portions. A pressure relief vents pressurized fluid from one of the first and second chamber portions to one other of the first and second chamber portions upon movement of the piston to a predetermined position. The pressure relief assembly includes a first valve at a first end of the pressure relief assembly and a second valve at a second end of the pressure relief assembly. The pressure relief assembly is axially movable relative to the piston to adjust the position of the first valve and the second valve relative to the piston.

A steering system is described for a vehicle having steerable wheels. A hydraulic charge pressure circuit may be configured to provide charge pressure to one or more hydraulic components of the vehicle and a hydraulic drive pressure circuit may be configured to provide working pressure to one or more other hydraulic components of the vehicle. Hydraulic machines may rotate front wheels in order to drive the vehicle, and a front valve assembly may control steering of the front wheels by controlling the hydraulic machines. The hydraulic machines may be driven to rotate the front wheels by the working pressure from the hydraulic drive pressure circuit, and the front valve assembly may control the front hydraulic machines to steer the agricultural vehicle by controlling flow of hydraulic fluid from the hydraulic charge pressure circuit through the front valve assembly.