Abstract: Vehicle power steering systems (710, 760, 810 and 910) achieve substantially linear control relationships between and applied steering torque input Ts and a resulting steering force output, that is, a powered assist to vehicle steering. Impedance matching means utilized for coupling an electric motor (26) to the steering load respectively include speed reduction means (712), torque summing means (812) and force generating means (912) in the systems (710, 760, 810 and 910). The speed reduction means (712) comprises gear reduction means (722) and a supplemental pinion. The torque summing means (812) comprises steering column (814) coupled gear reduction means (822), and, the force generating means (912) comprises hydraulic transmission means including a power cylinder (18). The systems (710, 760, 810 and 910) are preferably regenerative.

Abstract: A vehicle power steering system 10 achieves a substantially linear control relationship between an applied steering torque input T.sub.s and a resulting steering force output, that is, a powered assist to vehicle steering. The system 10 includes a reversible fluid pump 24 driven by an electric motor 26. A pair of fluid lines 20 and 22 supply pressurized fluid from the pump 24 and to the left and right ports 56 and 58 of a power cylinder 18. A pair of pressure transducers 54 and 55 sense the fluid pressures LP.sub.p and RP.sub.p in the lines 20 and 22. The pressure transducers 54 and 55 are connected to an electronic control 32 which establishes an internal closed servo control loop 322 or 342 over the powered assist to vehicle steering provided by the power cylinder 18, for example, over actuation of the motor 26. The system 10 is preferably regenerative and includes a variety of safety features which prevent system runaway and allow unencumbered manual steering in case of failure of the system.

Abstract: A yoke assembly for a rack and pinion steering system includes a bearing disc member having a pair of bearing surfaces for slidingly supporting and urging the rack toward the pinion. The bearing disc member is kinematically supported by elastomeric members along an adjustment axis. In the pitch direction elastomerically derived forces are applied toward an apex located well within the rack and away from the bearing surfaces. This results in the bearing disc member rotating slightly in a contra-pitch direction and forming a lubrication wedge whenever the rack moves along its axis of translation. Additionally along the adjustment axis, the bearing disc is supplementally supported in a stiffer manner in opposition to heavy shock loads. In the yaw direction, elastomerically derived forces are laterally directed to compliantly bias the bearing disc in a lateral direction orthogonal to a plane defined by the adjustment and translation axes toward a preferred central location.

Abstract: A regenerative power steering system 10 for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn. The system comprises a motor pump 24 connected to a fluid delivery line 20 and a reservoir structure 76, in turn connected to a closed-center control valve assembly 38 for actuating a power cylinder 18 connected to the vehicle wheels. The pump 24 is connected to the delivery line 20 and the reservoir structure 76 by a four-way cross-over valve 30.

Abstract: A yoke apparatus 34 is useful with a steering system having a pinion gear 20 and a longitudinally movable rack 24 engaged with the pinion gear 20. The yoke apparatus 34 comprises a bearing disc 36 received in the aperture 32, and a pair of biasing members 40 and 38 disposed in parallel with one another, each biasing the bearing disc 36 against the rack 24. This in turn biases the rack 24 against the pinion gear 20. The biasing members 40 and 38 have different spring constants and different compliances. Preferably, one of the biasing members 40 and 38 is a compression spring member 40 while the other is an elastomeric O-ring member 38, or other elastomeric member having a highly non-linear compliance. The yoke apparatus 34 also preferably comprises a plug 42 adjustably received in the aperture 32 which applies an axial load to the pair of biasing members 40 and 38.

Abstract: A yoke apparatus for use with a rack and pinion steering system includes a bearing disc member having a bearing surface for supporting the rack and a pair of angled outer surfaces disposed beneath the bearing surface for receiving arms of a biasing member. The biasing member includes a relief spring forming the pair of arms which are encapsulated in resilient material. The biasing member has a bottom surface with at least one recess for receiving a block portion of a support member. The arms of the biasing member compliantly urge the bearing disc into position against the rack while constraining the disc in lateral directions with respect to the housing bore.

Abstract: A yoke assembly for a rack and pinion steering system includes a bearing disc member having a pair of bearing surfaces for slidingly supporting and urging the rack toward the pinion. The bearing disc member is kinematically supported by an elastomeric member along an adjustment axis. The elastomeric forces are conically applied toward an apex located well within the rack and away from the bearing surfaces. This results in the bearing disc member rotating slightly in a contra-pitch direction and forming a lubrication wedge whenever the rack moves along its axis of translation. In addition, elastomeric means for compliantly biasing the bearing disc in a lateral direction orthogonal to a plane defined by the adjustment and translation axes toward a preferred central location are disclosed.

Abstract: A yoke assembly for a rack and pinion steering system includes a bearing disc member having a pair of bearing surfaces for slidingly supporting and urging the rack toward the pinion. The bearing disc member is kinematically supported by an elastomeric member. The elastomeric forces are conically applied toward an apex located well within the rack and away from the bearing surfaces. This results in the bearing disc member rotating slightly in a contra-pitch direction and forming a lubrication wedge whenever the rack moves along its axis of translation. The yoke assembly is of a compact design that can be substituted for the yoke assembly of any conventional rack and pinion steering system.

Abstract: Methods and devices for reducing instability in hydraulic systems are disclosed. A flow control device having an output fitting and a spring-biased piston reciprocally movable in a cylinder past a bypass hole is disclosed. The improvement consisting of metering passages formed in a flow control device to provide hydraulic resistance to dampen the piston. Alternatively, disclosed is a flow control piston having a valving sub-assembly which is resiliently biased. The valving sub-assembly is movable to substantially suppress the flow rate ripple by bypassing a dominant portion of the flow rate ripple. Finally, methods for dampening the resonance, creating resistance, as well as bypassing the flow rate ripple are disclosed.

Abstract: Methods and apparatus for improving control of pressurized fluid flow through bootstrap power steering systems are disclosed. In particular, the methods include differentially measuring control pressure across internal flow control orifices as directly as possible. Differential control pressure measurements are made between Kelvin supply, or return, pressure values and a control pressure port of a control valve. In addition, methods and apparatus for improved speed sensitive control of steering assist and/or driver selectable steering effort are also disclosed. One of the methods comprises an extension of the method of differentially measuring control pressure across the internal flow control orifices wherein a range of control pressures are enabled. In addition, a method of improving low speed tactile steering feel wherein an electronically variable orifice is activated in order to provide additional fluid flow thereby increasing "on-center" hydraulic pressure gain is disclosed.

Abstract: A bifurcated rack bearing assembly for a steering system includes a bearing member having a pair of bearing surfaces and which is pivotable within a base. The bearing member has a pair of curved riding surfaces which slide on a curved saddle surface of the base to permit the bearing surfaces to pivot into alignment coaxial with an axis of translation of the rack. The bifurcated rack bearing assembly can be substituted for the rack bearings of conventional steering systems.

Abstract: Methods and machining apparatus for indexing and forming spool and pinion shafts for use in a rotary control valve of a power steering system are disclosed. In particular, the methods include forming a contoured spool shaft extension on an end of a spool shaft and a complementary rosette on an end of a pinion shaft, and forming spool and pinion shaft holders having complementary rosettes and contoured ends, respectively, to permit accurate mounting of the spool and pinion shafts during subsequent machine operations. The machining apparatus includes a workpiece holder which rotates the spool or pinion shaft at a predetermined speed and a cutting assembly which moves a cutting tool into and out of contact with the workpiece at three times the speed of rotation of the workpiece.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. An improved isolating hose assembly comprising first, second and third volumetrically compliant members with first and second inductive flow members providing fluidic coupling therebetween is disclosed. The improved isolating hose assembly acts similarly to an electronic low pass filter network in deterring fluid borne noise from entering portions of the hydraulic system located therebeyond. A modified isolating hose assembly comprising a resistive member introduced within the second volumetrically compliant member in order to eliminate the possibility of a deleterious resonance in the assembly is disclosed. In addition, apparatus for additionally reducing structure borne noise in hydraulic systems comprising direct hydraulic coupling of the first volumetrically compliant member to internal output ports of the hydraulic system's pump is disclosed.

Abstract: Methods and devices for enabling simplified bootstrap hydraulic systems for use in bootstrap hydromechanical and electrohydraulic vehicular power steering systems are disclosed. A simplified bootstrap control valve is provided wherein the control valve's load circuit is not interdicted in any way. The simplified bootstrap control valve comprises a four-way control valve having input slots formed in an open-center manner, intermediate slots formed in an open-center manner, return slots formed in a closed-center manner, and a passage for picking off the pressure value present in the intermediate slots. The pressure value present in the intermediate slots is utilized for regulating pumping apparatus providing fluid to the simplified bootstrap control valve such that pressure value present in the intermediate slots is substantially maintained at a preselected value. A simplified servo motor-positive displacement pump assembly of integrated construction is also provided.

Abstract: A bifurcated rack bearing assembly for a steering system includes a bearing member having a pair of bearing surfaces and which is pivotable within a base. The bearing member has a pair of curved riding surfaces which slide on a curved saddle surface of the base to permit the bearing surfaces to pivot into alignment coaxial with an axis of translation of the rack. The bifurcated rack bearing assembly can be substituted for the rack bearings of conventional steering systems.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. The apparatus is an improved isolating hose assembly having first and second volumetrically compliant sections fluidly connected by an inductive flow member. Each of the first and second volumetrically compliant sections may, in addition, include a resistive flow element. The resistive flow elements are used to eliminate resonant conditions in the first and second volumetrically compliant sections at selected frequencies where capacitive behavior thereof would otherwise be compromised.

Abstract: The present invention is directed to a vehicular power steering system having an "open-center" control valve that has substantially zero hydraulic flow gain at zero input deflection angle and yet has minimal control orifice area. An improved valving sub-assembly is used in the control valve with functions to rapidly restore hydraulic gain at relatively small input deflection angles. The improved valving arrangement includes small transverse leakage slots formed in a valve spool that are in fluid communication with either input or return flow distribution slots. The leakage slots are configured to form parasitic flow orifices which fluidically interconnect the output slots formed in the valve sleeve and which communicate with the fluid chambers formed on opposite sides of the piston in the power cylinder. Accordingly, a selectively variable leakage path is provided across the power cylinder.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. An improved isolating hose assembly comprising first and second volumetrically compliant members with an inductive flow member providing fluidic coupling therebetween is disclosed. The improved isolating hose assembly acts similarly to an electronic low pass filter network in deterring fluid borne noise from entering portions of the hydraulic system located therebeyond. In addition, a sound barrier comprising a heavy-walled boot surrounding the first volumetrically compliant member is disclosed. The heavy-walled boot surrounding the first volumetrically compliant member acts to prevent acoustic sound sourced at the wall surface thereof from entering the surrounding atmosphere.

Abstract: Methods and devices for enhancing bootstrap hydraulic systems for use in vehicular power steering systems are disclosed. Improved pressure dividing networks are provided for enabling balanced operation of supply pressure control function when valve input shaft and sleeve are in relative centered positions or for enabling a first method of providing speed sensitive control of steering assist. Control valves utilizing a combination of open-center and closed-center flow control orifices are provided for reducing parasitic pressure losses. An improved variable displacement pump is provided for enabling volumetric flow rate efficient operation of bootstrap systems. A vehicular speed dependent command signal for a servo motor powered bootstrap hydraulic system is utilized in another method of providing speed sensitive control of steering assist.

Abstract: A flow control valve having a piston and valve element connected together by a portion of a spring also connected to a pressure relief mechanism. Also disclosed is an alternative embodiment featuring a passage delivering metered flow from an input passage to a low pressure end of a piston and then through a pressure sensing means from the low pressure chamber to an output passage. A valving sub-assembly is movable to substantially suppress the flow rate ripple by bypassing a dominant portion of the flow rate ripple.