A linear motion guide unit comprising a guide rail having first lengthwise raceway grooves on both longitudinal sides thereof, a slider that fits over or conforms to the guide rail and has second raceway grooves extending lengthwise in opposition to the first raceway grooves, and a plurality of ball rolling elements rolling through circulating circuits made up of races defined between the first raceway grooves and the second raceway grooves, return passages extending in the slider in parallel with the races, and turnaround passages connecting the races with the return passages in the slider;
- wherein the slider is composed of a carriage which is made up of a flat upper portion spreading above and in opposition to a top surface of the guide rail and side bulges lying on widthwise opposite sides of the upper portion to extend downward alongside of the longitudinal sides of the guide rail and further having the second raceway grooves on inside surfaces thereof,
- a pair of end caps secured on lengthwise opposite ends of the carriage, one to each end, and provided therein with the turnaround passages, a pair of cylindrical tubular members lying on outsides of the side bulges of the carriage to extend in a longitudinal direction, the tubular members having circular through-holes serving as the return passages, and
- a pair of coverings connected with the end caps to embrace the tubular members in combination with the outsides of the side bulges of the carriage,
- wherein the outsides of the side bulges of the carriage have lengthwise outward open recesses which are open outward to fit over or conform to outer cylindrical surfaces of the tubular members to keep the tubular members in parallel lengthwise with respect to the second raceway grooves, the outward open recesses being each constituted with a circular concave portion in a cross section extending lengthwise of the carriage while conforming to the outer cylindrical surface of the tubular member, an upper relief side or relief portion extending lengthwise of an upper edge of the circular concave portion, and a lower relief side or portion extending lengthwise of a lower edge of the circular concave portion, and further wherein the circular concave portion fits over the outer cylindrical surface of the tubular member, the upper relief side being formed to be separated by a difference above a horizontal level of the upper edge of the circular concave portion to provide a clearance spaced away from the outer cylindrical surface of the tubular member, and the lower relief side being formed to provide a clearance spaced away from the outer cylindrical surface of the tubular member, the clearance of the lower relief side being defined by a tangential line or surface extending downwards from the circular concave portion at a preselected angle with respect to the horizontal level,
- wherein the covering has an inner circular surface extended lengthwise and concaved in an arc in a cross section so as to make abutment against the outer cylindrical surface of the tubular member to embrace or cover over a substantial half of the outer cylindrical surface of the tubular member, the covering having a contour constituted with a side wall and a bottom wall extending together lengthwise to form a L-shape in a cross section, the bottom wall having a lengthwise edge formed into a lengthwise tongue having a wedged shape in a transverse section, and the lengthwise tongue extending in the clearance defined between the tubular member and the lower relief side of the carriage to wedge or retain in place the tubular member,
- wherein the lengthwise side wall of the covering has a lengthwise side surface set back with respect to a lengthwise outside of the carriage, and the lengthwise bottom wall of the covering has a bottom surface set back with respect to a lower surface of the carriage, and
- wherein the tubular member has a porous or cellular structure and lubricant retained in the tubular member gets oozed out of pores or cells of the porous structure to apply the lubricant around the ball rolling elements by a stress or impact of the ball rolling elements as the ball rolling elements roll through the return passages.