An electric power steering apparatus includes: a pinion shaft connected to a steering shaft coupled to a steering wheel, the pinion shaft being configured to transmit an operation of the steering wheel by a driver; a rack bar elongated along a lateral direction of a vehicle, having a first screw recess defined with a predetermined length in a portion of an outer circumferential surface of the rack bar, and including, on one side, a rack gear coupled to and interlocked with the pinion shaft; a motor configured to generate a steering assist power in proportion to a steering torque applied to the steering wheel; and a roller screw unit rotatably engaged with and coupled to the first screw recess to transmit the steering assist power generated from the motor to the rack bar.

A cylindrical part of a rack retainer accommodation part and an adjust screw are caulked such that a plastic deformation region by caulking straddles both a female screw part of the cylindrical part and a male screw part of the adjust screw, and the adjust screw is loosened to a point where a set load that is a force by which the rack retainer urges a rack bar falls within a predetermined range. After the set load adjusting step, the caulking step is not performed again, and fluctuations in the set load associated with the impact of caulking work after the set load adjusting step can be suppressed. Thus, it is possible to suppress fluctuations in the urging force of the rack retainer applied to the rack bar caused by caulking work which stops the rotation between the rack retainer accommodation part and the adjust screw.

The disclosure provides a steering system for a vehicle. The steering system may include a steering rack and an electronic power steering (EPS) system. The EPS system may include an actuator that assists movement of the steering rack, a torque sensor; an angle sensor; and an EPS system controller. The EPS controller may be configured to determine a steering rack center point indicating a center of the steering rack between opposite maximum steering angles. The EPS controller may be configured to determine a vehicle center zero point. The EPS controller may be configured to store the vehicle center zero point in response to determining that the vehicle center zero point is within a threshold of the steering rack center point.

One aspect of this disclosure is directed to a steering system comprising a housing in which a steering rack is movably arranged and extends out of the housing on at least one side of the housing, the steering rack being connected with a tie rod via a ball joint, wherein the connection is covered by a protective bellows defining a central axis and the bellows further comprising a first end defining a first opening around the central axis, a second end defining a second opening around the central axis, and several annular folds arranged along the central axis between the first end and second end, and wherein the bellows comprises a plurality of skirts arranged along the central axis and extending away from the bellows.

Another aspect of this disclosure is directed to a protective bellows defining a central axis and comprising a first end defining a first opening around the central axis, a second end defining a second opening around the central axis, and several annular folds arranged along the central axis between the first end and second end, and the bellows comprises a plurality of skirts arranged along the central axis.

A rack housing has a concave portion first inclined surface 45 on the inner side surface of an engaging concave portion located on the opening side that is inclined in a direction toward the back side while going outward in the radial direction. The rack bush has a convex portion first inclined surface on the outer side surface of an engaging convex portion that faces the concave portion first inclined surface, and that is inclined in a direction toward the back side while going outward in the radial direction. The convex portion first inclined surface is pressed outward in the radial direction against the concave portion first inclined surface, and the other outer side surface of the engaging convex portion facing the back side is pressed in the axial direction against the other inner side surface of the engaging concave portion facing the opening side.

A steering device includes: a rack shaft; a rack housing; a pinion shaft that meshes with the rack shaft; a speed reducer having a worm wheel that is coupled to the pinion shaft and a worm shaft that meshes with the worm wheel; a speed reducer housing; a motor that drives the worm shaft; a plate-shaped cover that seals an opening of the speed reducer housing; and a breather valve that is mounted on the cover in a state of penetrating through the cover. An inner surface of the cover that faces the worm wheel has an entry restricting part that restricts entry of a lubricant into the breather valve.

Using an update amount, an update amount calculating circuit manipulates a phase-control angle so as to perform feedback control such that a steering torque corresponds to a target torque. The steering torque is obtained by reducing a steering torque in magnitude by a predetermined value. The phase-control angle is used to convert a current command value to a value of a fixed coordinate system, for example. Using a guard value, a guard processing circuit performs a guard process on a current command value set by a command value setting circuit, so that the current command value becomes the current command value. The guard value is used to determine an appropriate range for a variation in the current command value in accordance with an amount by which the steering torque exceeds in magnitude the target torque.

A rolled round steel material for a steering rack bar, having a chemical composition consisting of C: 0.38 to 0.55%, Si: not more than 1.0%, Mn: 0.20 to 2.0%, S: 0.005 to 0.10%, Cr: 0.01 to 2.0%, Al: 0.003 to 0.10%, and N: 0.003 to 0.03%, with the balance being Fe and impurities, and P being not more than 0.030% in the impurities, and a microstructure consisting of ferrite (F), lamellar pearlite (LP), and cementite (C). The average grain diameter of (F), an area fraction of (LP), and the number of particles of spheroidal cementite (SC) among C are controlled in a region from the surface to a position at ½ radius and in a central part of the material. An average aspect ratio of F is controlled in a region from a surface to a position at ½ radius.

A vehicular steering device includes a turning shaft, a housing storing therein the turning shaft, a stopper provided at a shaft end of the turning shaft, and an annular elastic body. An opening of the housing is formed in a U-shaped cross-sectional shape and in an annular shape opened toward the stopper by an external cylinder portion and an internal cylinder portion. The elastic body includes a first elastic portion and a second elastic portion. The first elastic portion is supported by an inner circumferential surface of the external cylinder portion and the bottom surface, and is provided with a first clearance from an outer circumferential surface of the internal cylinder portion. The second elastic portion extends toward the stopper from the first elastic portion, and is provided with a second clearance larger than the first clearance from the inner circumferential surface of the external cylinder portion.

A vehicle is provided of which the four wheels are steerable, and which is prevented from unexpectedly moving forward or backward when switching the travel mode. The vehicle includes a steering device for front right and front left wheels of the vehicle capable of steering the front right and front left wheels, respectively, in one and the other of the right and left directions, a steering device for rear right and rear left wheels of the vehicle configured, simultaneously when the steering device for the front right and front left wheels are actuated, to be capable of steering the rear right and rear left wheels in the other and the one of the right and left directions, respectively, and in-wheel motors provided in at least one of each of the front right and front left wheels and each of the rear right and rear left wheels.