There is provided a dual rack and pinion rotational inerter system for damping movement of a flight control surface of an aircraft having a support structure. The system has a flexible holding structure disposed between the flight control surface and the support structure. The system has a dual rack and pinion assembly held by the flexible holding structure. The system has a first terminal and a second terminal, coupled to the dual rack and pinion assembly. The first terminal is coupled to the flight control surface. The system has a pair of inertia wheels coupled to the flexible holding structure. The system has an axle element inserted through the inertia wheels, the flexible holding structure, and the dual rack and pinion assembly, such that when the flight control surface rotates, the dual rack and pinion rotational inerter system translates and rotates, and movement of the flight control surface is dampened.

A ball screw mechanism that allows a reduction in contact and friction between a retainer and a nut is provided. In a ball screw mechanism, a nut is threadedly engaged with a screw groove of a rack shaft through balls retained in a retainer groove of a retainer, and an axial force is applied to the rack shaft in accordance with rotation of the nut. The nut includes a uniform diameter portion having a uniform inside diameter and enlarged diameter portions each having an inside diameter larger than that of the uniform diameter portion. The enlarged diameter portions are provided at opposite axial ends of a region on an inner circumferential surface of the nut. The region faces the retainer groove and retainer ends adjoining to opposite axial ends of the retainer groove.

A ball screw device and a steering system that include a retainer having more uniform stiffness are provided. Between a rack shaft and a ball screw nut, a cylindrical retainer having a plurality of retainer grooves that retain balls in a rollable manner is provided. Each retainer groove has two short inner surfaces that intersect the extending direction of the retainer groove and two long inner surfaces that intersect these short inner surfaces and extend along the extending direction of the retainer groove. In each of interior-angle portions where the short inner surfaces and the long inner surfaces intersect, a corner round surface is formed. The radius of the corner round surface is set to be smaller than one half of the width of the retainer groove.

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 apparatus, a ball train including a plurality of main balls is housed in a raceway between a ball track of a ball nut and a ball track of a ball screw shaft. A coil spring housed in the raceway includes a first end that engages with an end of the ball train and a second end supported by a stopper (a first recessed portion, a protruding portion, or the like) of the ball nut. A stopper ball having a diameter larger than the diameter of the main ball is interposed between the stopper and the second end of the coil spring.

There is provided a dual rack and pinion rotational inerter system for damping movement of a flight control surface of an aircraft having a support structure. The system has a flexible holding structure disposed between the flight control surface and the support structure. The system has a dual rack and pinion assembly held by the flexible holding structure. The system has a first terminal and a second terminal, coupled to the dual rack and pinion assembly. The first terminal is coupled to the flight control surface. The system has a pair of inertia wheels coupled to the flexible holding structure. The system has an axle element inserted through the inertia wheels, the flexible holding structure, and the dual rack and pinion assembly, such that when the flight control surface rotates, the dual rack and pinion rotational inerter system translates and rotates, and movement of the flight control surface is dampened.

In an example, an apparatus may include a first elongated member having a hollow core and a first end, a second elongated member extending partially into the hollow core of the first elongated member, a driving mechanism to move the first elongated member with respect to the second elongated member to vary a distance between the first end and the second elongated member, and a control circuit housed within the second elongated member, in which the control circuit is to control the driving mechanism to vary a position of the first end with respect to the second elongated member. The apparatus may also include a load cell to detect a physical load applied onto the apparatus, in which the load cell is to communicate the detected physical load to the control circuit.

There is provided a dual rack and pinion rotational inerter system for damping movement of a flight control surface of an aircraft. The system has a flexible holding structure disposed between the flight control surface and a support structure of the aircraft. The system has a dual rack and pinion assembly held by and between the flexible holding structure. The dual rack and pinion assembly has a first rack, a second rack, and a pinion engaged to and between the racks. The system has a first terminal coupled to the first rack and coupled to the flight control surface, via a pivot element, and a second terminal coupled to the second rack, and coupled to the support structure. The system has a pair of inertia wheels adjacent the flexible holding structure. The system has an axle element inserted through the inertial wheels, the flexible holding structure, and the pinion.

A ball screw device includes a screw shaft, a nut, and a housing that has a bottomed cylindrical shape and to which the nut is attached. The ball screw device converts rotational motion of the screw shaft into linear motion of the housing. The ball screw device is switched between a normal use state and a supply state. In the normal use state, along with the linear motion, a bottom portion of the housing reciprocates between a first position spaced apart from an end of the screw shaft and a second position closer to the end. In the supply state, along with the linear motion, the bottom portion of the housing is located in a third position even closer to the end of the screw shaft, such that grease present in the nut and the bottom portion of the housing is introduced to a radially inner side of the nut.

A ball screw device is provided, including a retainer that can properly retain balls. The difference between a diameter being the pitch circle diameter of the ball screw device and the outside diameter of the rack shaft is set to be equal to or larger than the difference between the bore diameter of a ball screw nut and the diameter. The thickness center diameter of the retainer is set to be smaller than the diameter. Even when the inclination angle is reduced, the clearance between the inclined surfaces of each retainer groove on the radial inside can be easily set to be smaller than the diameter of the balls because the bore diameter of the retainer is set to be smaller. Thus, even when the inclination angle of the inclined surfaces is set to be smaller, the balls can be properly retained.