The invention relates to a power steering system for a working machine, said power steering system comprising at least one steering cylinder comprising two compartments separated by a piston, a tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered liquid flow, a hydraulic pump for pumping liquid from the tank to the steering unit through a supply line (SL), a return line (RL) through which the liquid flows back to the tank, a recirculation line connecting the RL to the SL, a check valve being arranged on said recirculation line to prevent liquid from flowing from the SL to the RL, two control lines, respectively connecting the steering unit to the two compartments and a liquid accumulator connected through a branch to the RL. A relief valve is arranged on the RL between the tank and an accumulator connection point.

The invention relates to a power steering system for a working machine, said power steering system comprising at least one steering cylinder comprising two compartments separated by a piston, a tank, a steering unit comprising a steering valve and a metering device, for supplying one compartment of the steering cylinder with a metered liquid flow, a hydraulic pump for pumping liquid from the tank to the steering unit through a supply line (SL), a return line (RL) through which the liquid flows back to the tank, a recirculation line connecting the RL to the SL, a check valve being arranged on said recirculation line to prevent liquid from flowing from the SL to the RL, two control lines, respectively connecting the steering unit to the two compartments and a liquid accumulator connected through a branch to the RL. A relief valve is arranged on the RL between the tank and an accumulator connection point.

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.

An electric power steering device includes: —a steering column provided with: a base; an upper segment connected in a tiltable manner to the base, a steering axis comprising a lower axis rotatably contained inside the base; —a hydrostatic steering assembly; —an electrically assisted steering apparatus axially interposed between the steering column and the hydrostatic steering assembly and provided with: a support frame comprising a tubular central body; a shaft whose upper end axially projects outside an upper end of the central body and is connected to the lower end of the lower axis and whose lower end is connected to the hydrostatic steering assembly; and an electric motor positioned inside the central body of the support frame; in which the upper end of the central body is directly fixed to the base and in contact therewith.

The invention relates to a hydraulic steering unit (1) including a housing (3), a spool, a sleeve (12) arranged between spool and housing (3), and a measuring motor (14) having a number of working chambers (15), wherein a first commutation geometry (18) and a second commutation geometry (19) are arranged between the sleeve (12) and the housing (3), wherein the commutation geometries (18, 19) are connected to the working chambers (15) of the measuring motor (14) and the housing includes a first direction port (4), a second direction port (5), a pressure port (6), and a return port (7). The object is to have a good steering behavior. To this end one of the commutation geometries (18) is directly connected to the first direction port (4).

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.

This power steering valve (1) includes a sleeve (40), a spool (60) held in such a way as to be able to rotate within the housing (40), to which an input shaft U of a steering wheel S is coupled, a gerotor (30) fixed to the sleeve (10) and configured to be driven by hydraulic fluid which flows out from the predetermined opening of the sleeve (40), and a drive shaft (80) meshing with an inner rotor (32) of the gerotor (30) and pivotally supported in a swingable manner by the sleeve (40) with use of a pin (81), wherein an overall length Ld of the drive shaft (80) is formed to have a dimension defined by (¼).Math.Ls≤Ld≤(½).Math.Ls relative to an overall length Ls of the sleeve (40), and the pin (81) is arranged at a position nearer the gerotor (30) in an axial direction than a middle position in the sleeve (40).

This power steering valve (1) includes a sleeve (40), a spool (60) held in such a way as to be able to rotate within the housing (40), to which an input shaft U of a steering wheel S is coupled, a gerotor (30) fixed to the sleeve (10) and configured to be driven by hydraulic fluid which flows out from the predetermined opening of the sleeve (40), and a drive shaft (80) meshing with an inner rotor (32) of the gerotor (30) and pivotally supported in a swingable manner by the sleeve (40) with use of a pin (81), wherein an overall length Ld of the drive shaft (80) is formed to have a dimension defined by (¼).Math.Ls≤Ld≤(½).Math.Ls relative to an overall length Ls of the sleeve (40), and the pin (81) is arranged at a position nearer the gerotor (30) in an axial direction than a middle position in the sleeve (40).

A fluid controller (1), in particular as part of a hydraulic steering unit, is described said controller (1) comprising a housing (2) having a supply port arrangement, a sleeve (4) arranged rotatably in a bore of the housing (2), a spool (3) arranged rotatably in the sleeve (4), and a measuring motor, wherein the measuring motor comprises a plurality of working chambers, each working chamber being connected to the bore, wherein the sleeve (4) comprises a commutation geometry (7) having a first partition and controlling together with a housing geometry (5) of the housing (2) a flow of hydraulic fluid into and out of the working chambers and the spool (3) comprises a spool geometry (14) controlling together with a valve geometry (10, 11) of the sleeve (4) a flow of hydraulic fluid between the supply port arrangement and the commutation geometry. Such a fluid controller should have a stable control behavior. To this end the valve geometry (10,11) comprises a second partition different from the first partition.

The invention relates to a hydraulic steering unit (1) including a housing (3), a spool, a sleeve (12) arranged between spool and housing (3), and a measuring motor (14) having a number of working chambers (15), wherein a first commutation geometry (18) and a second commutation geometry (19) are arranged between the sleeve (12) and the housing (3), wherein the commutation geometries (18, 19) are connected to the working chambers (15) of the measuring motor (14) and the housing includes a first direction port (4), a second direction port (5), a pressure port (6), and a return port (7). The object is to have a good steering behavior. To this end one of the commutation geometries (18) is directly connected to the first direction port (4).