Slide rail device for vehicle seat

Abstract

A slide rail device which includes a lower rail, an upper rail which is freely slidably engaged with the lower rail, and balls which are installed between the lower and upper rails. The lower rail includes a lower-rail bottom wall, a pair of lower-rail side walls, a pair of lower-rail upper walls, a pair of lower-rail lower-ball contact R-portions, and a pair of lower-rail upper-ball contact R-portions. The upper rail includes an upper-rail top wall, a pair of upper-rail side walls, and a pair of upper-rail ball-bearing walls. Each upper-rail ball-bearing wall includes an upper-rail lower-ball contact portion and an upper-rail upper-ball contact portion. A radius of curvature of the lower-rail lower-ball contact R-portion of the lower rail is greater than that of the lower ball, and a radius of curvature of the lower-rail upper-ball contact R-portion of the lower rail is greater than that of the upper ball.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a slide rail device for making an adjustment to the position of a vehicle seat in the forward / rearward direction.[0003]2. Description of Related Art[0004]A typical slide rail device (slide rail assembly) is configured of a lower rail that is fixed to a vehicle floor, an upper rail that is fixed to a vehicle seat and engaged with the lower rail to be freely slidable thereon, and balls (steel balls) for reducing frictional resistance that are installed between the upper rail and the lower rail. The upper rail and the lower rail are each made of a metallic material (usually an iron-based material) having a uniform cross section. Such a slide rail device is disclosed in Japanese Patent Publication No. 4,230,945.[0005]In this known slide rail device, application of a force on the upper rail and the lower rail therebetween that is produced by the weight of someone (a driver or a passenger) sit...

AI Technical Summary

Benefits of technology

The present invention provides a slide rail device with improved stability and rollability of the slide rails. The inventor found that by making the radius of balls and the radius of curvature of the ball contact portion of the rail equal, the possibility of unintentionally producing a ball and rail combination with a smaller radius of curvature in the ball contact portion of the rail is reduced. This results in a better rollability of the balls. The slide rail device includes a lower rail, an upper rail, and balls installed between the rails. The lower rail has a uniform cross section and a specific curvature in the ball contact portion. The upper rail has a flat surface or an upper-rail upper-ball contact portion that is formed into a circular arc shape with a specific curvature. The ratio of force to deformation of the rails is greater for the upper-rail upper-ball contact portion, so it is desirable to make it smaller in surface pressure than a flat surface. The upper-rail lower-ball contact portion can also be formed into a circular arc shape with a specific curvature. The technical effects of the invention include improved stability and rollability of the slide rails.

Problems solved by technology

However, the inventor of the present invention has found that, if the radius of the balls is made to be identical in design to the radius of curvature of the ball contact portions of each rail, the rollability of the balls sometimes deteriorates regardless of the presence or absence of indentations on the rails (aside from the problem of indentations), to thereby make the sliding operation of the upper rail with respect to the lower rail unstable.

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