The present invention is an improved version of the steering system described in U.S. patent application Ser. No. 17/115,573. The prior steering system features effortless steering input from the driver and negligible bumpsteer during suspension operation. Such extraordinary steering performance is realized with the use of costly and complex electric assist devices and control devices. The present steering system includes an alternative electric assist device which allows for the removal of the costly and complex electric assist devices in the prior steering system. The present steering system also includes a novel hydraulic control valve with a solenoid valve-plunger mechanism. The mechanism prevents premature wear or destruction of the rack and pinion gearset. The use of the alternative electric assist device and hydraulic control valve enables the present steering system to preserve the extraordinary steering performance featured in the prior steering system concurrent with a reduction in cost and complexity.

A steering system includes a steering control, a steering assist assembly, and two anti-rotation arms. The steering assist assembly includes a housing includes two hollow cylinders formed therein. A piston is slidably arranged within the first cylinder and an axial rod is slidably arranged within the second cylinder. First and second tie rods are connected to first and second axial ends of the axial rod. A shaft operably connected to the steering control is configured to engage with the axial rod such that rotation of the shaft causes axial movement of the axial rod. The axial movement of the axial rod causes axial movement of the first and second tie rods so as to turn the wheels of the vehicle. The anti-rotation arms are operably connected to the piston and to the axial rod and are configured to prevent rotation of the piston and the axial rod.

A hydrostatic drive includes a transmission having a pump and motor disposed on a center section, and a charge pump to provide fluid to a charge gallery. A power take off (PTO) driven by a prime mover includes a clutch assembly, solenoid valve, and PTO drive member driven by a prime mover input. When the solenoid valve is in a first position, fluid flows from the charge gallery to the clutch to connect the input with the PTO drive member, and when the solenoid valve is in a second position, fluid flows from the PTO mechanism to the sump to disengage the PTO drive member from the input. A filter may be disposed on a land on the center section and seated in a filter pocket in the housing. The filter engages with a bottom surface of the filter pocket to maintain a seal against the land.

A hydrostatic drive includes a transmission having a pump and motor disposed on a center section, and a charge pump to provide fluid to a charge gallery. A power take off (PTO) driven by a prime mover includes a clutch assembly, solenoid valve, and PTO drive member driven by a prime mover input. When the solenoid valve is in a first position, fluid flows from the charge gallery to the clutch to connect the input with the PTO drive member, and when the solenoid valve is in a second position, fluid flows from the PTO mechanism to the sump to disengage the PTO drive member from the input. A filter may be disposed on a land on the center section and seated in a filter pocket in the housing. The filter engages with a bottom surface of the filter pocket to maintain a seal against the land.

A vehicle steering assembly that includes a housing, a pinion shaft, a seal, a protector and a dust cover. The housing defines a bore with the pinion shaft extending therethrough. The seal is disposed within the bore spaced apart from the end of the housing. The seal extends around the pinion shaft creating a seal therebetween. The housing and the pinion shaft define an annular space therebetween and between an opening at one end of the housing and the seal. The protector is fitted to the housing covering a portion of the opening and the annular space. The protector has a shaft receiving opening with the pinion shaft extending therethrough and out of the housing. The dust cover is attached to the housing completely covering the protector and the opening of the bore.

A vehicle steering assembly that includes a housing, a pinion shaft, a seal, a protector and a dust cover. The housing defines a bore with the pinion shaft extending therethrough. The seal is disposed within the bore spaced apart from the end of the housing. The seal extends around the pinion shaft creating a seal therebetween. The housing and the pinion shaft define an annular space therebetween and between an opening at one end of the housing and the seal. The protector is fitted to the housing covering a portion of the opening and the annular space. The protector has a shaft receiving opening with the pinion shaft extending therethrough and out of the housing. The dust cover is attached to the housing completely covering the protector and the opening of the bore.

A brake system for providing tactile feedback in a vehicle steering system. The brake system includes an input shaft, and a rotor responsive to the shaft to rotate in response to input steering wheel inputs. A friction element imparts a base load to the rotor, and an electromagnetic coil imparts a variable load to the rotor. A housing of the brake system includes a fixed component and an intermediate component threaded together to set the base load. An adjustable component of the housing is threaded to the intermediate component to calibrate the variable load. The friction element is disposed between, and engages, both the rotor and the intermediate housing to impart the feedback loads.

Self-propelled vehicles that include swiveling caster wheels and independent drive wheels are disclosed. The self-propelled vehicles are selectively steered in a caster wheel steering mode or a drive wheel steering mode. The vehicle includes a steering position sensor to measure the position of the steering system. A control unit varies the rotational speed of first and second drive wheels based at least in part of the signal from the steering position sensor.

In a ball screw device, an inner peripheral rolling groove of a nut includes, between openings of mounting holes, a constant pitch circle diameter region where a pitch circle diameter is constant and gradually-changing pitch circle diameter regions where the pitch circle diameter gradually increases, in the ranges from opposite ends of the constant pitch circle diameter region to the respective openings. At least the constant pitch circle diameter region has a surface hardness greater than or equal to a predetermined value, among the constant pitch circle diameter region and the gradually-changing pitch circle diameter regions excluding edges at the boundaries between the respective openings and the inner peripheral rolling groove, and the edges at the boundaries between the respective openings and the inner peripheral rolling groove have a surface hardness less than the predetermined value.

In a ball screw device, an inner peripheral rolling groove of a nut includes, between openings of mounting holes, a constant pitch circle diameter region where a pitch circle diameter is constant and gradually-changing pitch circle diameter regions where the pitch circle diameter gradually increases, in the ranges from opposite ends of the constant pitch circle diameter region to the respective openings. At least the constant pitch circle diameter region has a surface hardness greater than or equal to a predetermined value, among the constant pitch circle diameter region and the gradually-changing pitch circle diameter regions excluding edges at the boundaries between the respective openings and the inner peripheral rolling groove, and the edges at the boundaries between the respective openings and the inner peripheral rolling groove have a surface hardness less than the predetermined value.