JP2007002858A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly impart preload axially and radially between ball nuts halved axially in the ball screw shaft and the ball screw shaft. <P>SOLUTION: In the ball screw device A1, the ball nuts 13, 14 halved axially in the ball screw shaft 11 are fit in the ball screw shaft 11 by means of a number of balls 12, the ball nut 14 is positionally adjustable relative to the ball nut 13 in the axial direction of the ball screw shaft. In both the ball nuts 13, 14, respective opposite end faces 13a, 14a are tapered, and the ball nuts 13, 14 are axially movably built in a cylindrical nut holder 15 placed on the outside periphery of the ball screw shaft 11. An adjusting member 17 engaged with the tapered end faces 13a, 14a is incorporated in the nut holder 15 axially movably in the radial direction of the ball screw shaft. The adjusting member 17 is pushed radially from outside the ball screw shaft 11 into the inside, thus ball nuts 13, 14 are each fixed apart in the axial direction of the ball screw shaft. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball screw device in which a ball nut is fitted to a ball screw shaft through a large number of balls, for example, a ball screw shaft is provided coaxially and integrally with a steering rack shaft, and the ball nut is mounted by an electric motor. The present invention relates to a ball screw device that can be employed in an electric power steering device for a vehicle that can move in the axial direction by rotating and driving a ball screw shaft and a steering rack shaft.

This type of ball screw device is described, for example, in Patent Document 1 below. In the ball screw device described in Patent Document 1, the ball nut is divided into two in the axial direction of the ball screw shaft, and each ball nut is connected via a detent means that allows movement in the axial direction. The inner ring of the double row support bearing is provided on the outer peripheral side of both ball nuts so as to be movable in the axial direction, and the inner ring is divided in the axial direction between the double row rolling elements. A preloading nut for pressing one inner ring in the axial direction is attached to a threaded portion provided on the inner surface of the screw.
JP-A-6-74315

  In the ball screw device of Patent Document 1 described above, there is an advantage that preload can be simultaneously applied to the ball screw and the support bearing by moving the preload nut with respect to the threaded portion, but the preload applied to the ball screw is also provided. And the preload applied to the support bearing may interfere with each other, and the preload may not be applied accurately to the ball screw. In this ball screw device, since the preload is in the axial direction, each axial gap between the ball and the ball nut and between the ball and the ball screw shaft can be accurately adjusted. In addition, the radial gaps between the ball and the ball screw shaft may not be adjusted accurately.

  The present invention has been made to cope with the above-described problem, and a ball nut fitted to a ball screw shaft through a large number of balls is divided into two in the axial direction of the ball screw shaft, In the ball screw device in which the position of the other ball nut can be adjusted in the axial direction of the ball screw shaft with respect to the ball nut, the opposite end surfaces of each of the ball nuts are formed in a tapered shape. An adjustment member that is assembled in a cylindrical nut holder provided on the outer periphery of the ball screw shaft so as to be movable in the axial direction of the ball screw shaft, and can be engaged with a tapered end surface of each of the ball nuts. Is assembled to the nut holder so as to be movable in the radial direction of the ball screw shaft, and the adjusting member is fixed by being pushed inwardly from the outside of the ball screw shaft. The is characterized in that each ball nut is set to be fixed at a distance from each other in the axial direction of the ball screw shaft.

  In this ball screw device, the adjusting member assembled in the nut holder is pressed and fixed from the outside of the ball screw shaft to the inside of the diameter to thereby apply pressure to the tapered end surfaces of both ball nuts. It is possible to accurately apply axial preload between both ball nuts and ball screw shafts that are engaged via a large number of balls, and to accurately apply radial preload. It is possible to give to. For this reason, it is possible to accurately adjust both the axial gap and the radial gap between the ball and the ball nut and between the ball and the ball screw shaft.

  In carrying out the present invention, the other ball nut, whose position is adjustable in the axial direction with respect to one ball nut, is assembled to the nut holder so that the position can be adjusted in the axial direction of the ball screw shaft. It is also possible to adjust the position in the axial direction of the ball screw shaft by the adjustment nut attached. In this case, the axial position of the other ball nut with respect to one ball nut is largely adjusted with the adjusting nut, and then each axial gap and each radial gap between the ball and the ball nut, and between the ball and the ball screw shaft. Can be finely adjusted with the adjusting member.

  In carrying out the present invention, a plurality of adjusting members may be provided in the circumferential direction of the ball screw shaft. In this case, it is possible to adjust each axial gap and each radial gap between the ball and the ball nut and between the ball and the ball screw shaft in a well-balanced manner while aligning each ball nut with the ball screw shaft. is there.

  Further, when the present invention is carried out, the adjustment member is screwed to the nut holder so that the adjustment member can be advanced and retracted, and the adjustment amount of the adjustment member can adjust the radial movement position of the adjustment member. It is also possible. In this case, the space that must be secured on the outer periphery of the nut holder can be reduced, and space saving can be achieved.

  In carrying out the present invention, the adjustment member protrudes radially outward from the outer periphery of the nut holder, and is attached to the outer periphery of the nut holder and engages with the radially outer end of the adjustment member. It is also possible to adjust the push-in amount radially inward by a single adjustment screw that can adjust the tightening amount of the tightening band. In this case, by adjusting a single adjustment screw on the outer periphery of the nut holder, it is possible to adjust each axial gap and each radial gap between the ball and the ball nut and between the ball and the ball screw shaft. Workability can be improved. Further, when there are a plurality of adjusting members, it is possible to adjust a plurality of adjusting members at once by adjusting one adjusting screw and adjusting the tightening amount of the tightening band. .

  Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 schematically show a first embodiment of a ball screw device according to the present invention. In the ball screw device A1 of the first embodiment, a large number of balls 12 are arranged on the outer periphery of a ball screw shaft 11. FIG. A pair of ball nuts 13 and 14 divided into two in the axial direction of the ball screw shaft 11 are fitted. When the ball screw device A1 is employed in an electric power steering device for a vehicle, the ball screw shaft 11 is coaxially and integrally connected to a steering rack shaft (not shown), and the ball is driven by an electric motor (not shown). When the nuts 13 and 14 are rotationally driven without moving in the axial direction, the ball screw shaft 11 and the steering rack shaft can be moved in the axial direction.

  Both ball nuts 13, 14 are formed with tapered end faces 13 a, 14 a in a tapered shape. The screw shaft 11 is assembled so as to be movable in the axial direction. One ball nut 13 is fitted and fixed to the inner hole step portion 15 b of the nut holder 15. The other ball nut 14 is attached to the ball nut 13 with respect to one ball nut 13 by an adjusting nut 16 screwed to the large-diameter threaded portion 15c of the nut holder 15 so that the position of the ball nut 14 can be adjusted in the axial direction of the ball screw shaft 11. The position can be adjusted in 11 axial directions.

  Moreover, in this ball screw apparatus A1, the three adjustment members 17 which can be engaged with the taper-shaped end surfaces 13a and 14a of each ball nut 13 and 14 and were provided at equal intervals in the circumferential direction of the ball screw shaft 11 include The nut holder 15 is assembled so as to be movable in the radial direction of the ball screw shaft 11. Further, each adjusting member 17 is pushed and fixed from the outside of the ball screw shaft 11 to the inside by the adjusting screw 18 so that the ball nuts 13 and 14 are separated from each other in the axial direction of the ball screw shaft 11. Are set to be fixed.

  Each adjustment member 17 has a pair of inclined surfaces 17a that engage with the tapered end surfaces 13a and 14a of the ball nuts 13 and 14, and is formed in a wedge shape. The adjustment screw 18 screwed to enable adjustment of the radial movement position, that is, the amount of pushing inward in the radial direction. Each adjustment screw 18 has a hexagonal hole 18 a on the outer peripheral side of the nut holder 15, and the screwing amount can be adjusted by adjustment work from the outer peripheral side of the nut holder 15.

  In the ball screw device A1 configured as described above, each adjustment member 17 assembled in the nut holder 15 is pushed inward from the radially outer side of the ball screw shaft 11 through the small-diameter screw portion 15d of the nut holder 15. By fixing, pressure can be applied from the inclined surface 17a of each adjusting member 17 to the tapered end surfaces 13a, 14a of the ball nuts 13, 14, and both of them engaged through a large number of balls 12 are engaged. Between the ball nuts 13 and 14 and the ball screw shaft 11, an axial preload can be accurately applied, and a radial preload can be accurately applied. Therefore, it is possible to accurately adjust both the axial gaps and the radial gaps between the ball 12 and the ball nuts 13 and 14 and between the ball 12 and the ball screw shaft 11.

  In the ball screw device A1, the other ball nut 14 that can be adjusted in the axial direction with respect to one ball nut 13 is positioned in the nut holder 15 in the axial direction of the ball screw shaft 11. The position can be adjusted in the axial direction of the ball screw shaft 11 by an adjustment nut 16 assembled in an adjustable manner. Therefore, after the position of the other ball nut 14 in the axial direction of the other ball nut 13 with respect to the one ball nut 13 is largely adjusted by the adjustment nut 16, each axis between the ball 12 and the ball nuts 13, 14 and between the ball 12 and the ball screw shaft 11. The directional gap and the radial gaps can be finely adjusted by the adjusting member 17.

  In the ball screw device A1, three adjustment members 17 are provided at equal intervals in the circumferential direction of the ball screw shaft 11. Therefore, the axial gaps and radial gaps between the ball 12 and the ball nuts 13 and 14 and between the ball 12 and the ball screw shaft 11 are adjusted while aligning the ball nuts 13 and 14 with respect to the ball screw shaft 11. It is possible to adjust with good balance.

  Further, in this ball screw device A1, each adjustment member 17 is pushed inward in the radial direction by an adjustment screw 18 that is screwed to the nut holder 15 so as to be able to advance and retreat, and can adjust the radial movement position of the adjustment member 17. The amount is adjustable. For this reason, the space which must be ensured on the outer periphery of the nut holder 15 can be reduced, and space saving can be achieved.

  In the ball screw device A1 according to the first embodiment described above, the three adjusting members 17 are adjusted such that the amount of pressing inwardly by the three adjusting screws 18 can be adjusted. As in the second embodiment, the three adjusting members 117 can be adjusted so that the amount of pushing inwardly by the tightening band 118 and the single adjusting screw 119 can be adjusted. The configurations other than the adjustment member 117, the fastening band 118, and the adjustment screw 119 in the ball screw device A2 of the second embodiment are the same as the configurations other than the adjustment member 17 and the adjustment screw 18 in the ball screw device A1 of the first embodiment. Since they are substantially the same, the same reference numerals in the 100s are attached, and description thereof is omitted.

  Each adjustment member 117 of the second embodiment has a pair of inclined surfaces 117a that engage with the tapered end surfaces 113a and 114a of the ball nuts 113 and 114, is formed in a wedge shape, and is attached to the nut holder 115. The mounting hole 115d having a non-circular cross section is assembled so as to be movable in the radial direction of the ball screw shaft 111. Each adjustment member 117 protrudes radially outward from the outer periphery of the nut holder 115, and engages with the inner periphery of the tightening band 118 at the protruding end (diameter outer end).

  The tightening band 118 is attached to the outer periphery of the nut holder 115, has an opposite end portion 118 a, and engages with the radially outer end of each adjustment member 117. The adjusting screw 119 is screwed to the opposing end portion 118a of the tightening band 118, and the amount of tightening of the tightening band 118 can be adjusted, and the amount of pushing inwardly of each adjusting member 117 is adjusted. Is possible.

  In the ball screw device A2 of the second embodiment configured as described above, by pressing the respective adjustment members 117 assembled to the nut holder 115 from the radially outer side to the radially inner side of the ball screw shaft 111 and fixing, Both ball nuts 113, 114 that can apply pressure to the tapered end surfaces 113 a, 114 a of the ball nuts 113, 114 from the inclined surface 117 a of each adjustment member 117 and are engaged via a large number of balls 112. It is possible to accurately apply the axial preload between the ball screw shaft 111 and the radial preload. Therefore, it is possible to accurately adjust both the axial gaps and the radial gaps between the ball 112 and the ball nuts 113 and 114 and between the ball 112 and the ball screw shaft 111.

  Further, in this ball screw device A2, the other ball nut 114, whose position can be adjusted in the axial direction with respect to one ball nut 113, is positioned in the nut holder 115 in the axial direction of the ball screw shaft 111. The position can be adjusted in the axial direction of the ball screw shaft 111 by an adjustment nut 116 assembled in an adjustable manner. For this reason, after the axial position of the other ball nut 114 with respect to one ball nut 113 is largely adjusted by the adjusting nut 116, each axis between the ball 112 and the ball nut 113, 114 and between the ball 112 and the ball screw shaft 111 is adjusted. The directional gap and the radial gaps can be finely adjusted by the adjusting member 117.

  In the ball screw device A2, three adjustment members 117 are provided at equal intervals in the circumferential direction of the ball screw shaft 111. Therefore, while aligning the ball nuts 113 and 114 with respect to the ball screw shaft 111, the axial clearances and radial clearances between the ball 112 and the ball nuts 113 and 114 and between the ball 112 and the ball screw shaft 111 are increased. It is possible to adjust with good balance.

  Further, in this ball screw device A2, each adjustment member 117 protrudes radially outward from the outer periphery of the nut holder 115, and the diameter of the three adjustment members 117 is determined by the fastening band 118 and the single adjustment screw 119. The inward push amount can be adjusted. For this reason, by adjusting a single adjustment screw 119 on the outer periphery of the nut holder 115, it is possible to adjust the three adjustment members 117 in a lump, and between the ball 112 and the ball nuts 113, 114. In addition, it is possible to adjust the axial gaps and the radial gaps between the ball 112 and the ball screw shaft 111, thereby improving workability.

  In each of the embodiments described above, the number of the adjustment members 17 and 117 is three, but the number of the adjustment members 17 and 117 can be appropriately increased or decreased. In each of the above-described embodiments, the radial position of each adjustment member 17 can be adjusted by each adjustment screw 18, or all the adjustment members 117 can be adjusted by the fastening band 118 and a single adjustment screw 119. Although the present invention has been implemented with the configuration in which the radial position can be adjusted, the radial position adjusting means of each adjustment member is not limited to the configuration of each of the above embodiments, and the present invention is implemented with appropriate modifications. It is also possible.

FIG. 3 is a developed cross-sectional view taken along line 1-1 of FIG. 2 schematically illustrating a first embodiment of the ball screw device according to the present invention. FIG. 2 is a cross-sectional view taken along line 2-2 in FIG. FIG. 6 is a developed cross-sectional view taken along line 3-3 of FIG. 4 schematically illustrating a second embodiment of the ball screw device according to the present invention. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Ball screw shaft, 12 ... Ball, 13 ... One ball nut, 14 ... Other ball nut, 13a, 14a ... Tapered end surface, 15 ... Nut holder, 16 ... Adjustment nut, 17 ... Adjustment member, 18 ... Adjustment Screw, A1 ... Ball screw device, 111 ... Ball screw shaft, 112 ... Ball, 113 ... One ball nut, 114 ... Other ball nut, 113a, 114a ... Tapered end face, 115 ... Nut holder, 116 ... Adjustment nut, 117: adjusting member, 118: tightening band, 119: adjusting screw, A2: ball screw device

Claims (5)

  A ball nut fitted to the ball screw shaft via a large number of balls is divided into two in the axial direction of the ball screw shaft, and the other ball nut is the shaft of the ball screw shaft with respect to one ball nut. In the ball screw device whose position can be adjusted in the direction, each of the ball nuts has a taper shape at each of the opposing end faces, and is in a cylindrical nut holder provided on the outer periphery of the ball screw shaft. In addition, an adjustment member that is assembled so as to be movable in the axial direction of the ball screw shaft and engageable with the tapered end face of each ball nut is movable in the radial direction of the ball screw shaft to the nut holder. Each of the ball nuts is fixed in the axial direction of the ball screw shaft. Ball screw device characterized by being configured to be spaced apart and fixed.   2. The ball screw device according to claim 1, wherein the other ball nut that is axially adjustable with respect to one ball nut is adjusted in position in the axial direction of the ball screw shaft with respect to the nut holder. A ball screw device characterized in that the position can be adjusted in the axial direction of the ball screw shaft by means of an adjustment nut assembled in a possible manner.   3. The ball screw device according to claim 1, wherein a plurality of the adjustment members are provided in a circumferential direction of the ball screw shaft. 4.   The ball screw device according to any one of claims 1 to 3, wherein the adjustment member is screwed to the nut holder so as to advance and retreat, and an adjustment screw capable of adjusting a radial movement position of the adjustment member, A ball screw device characterized in that the amount of pushing inward in the diameter can be adjusted. The ball screw device according to any one of claims 1 to 3, wherein the adjustment member protrudes radially outward from an outer periphery of the nut holder, and is attached to the outer periphery of the nut holder. A ball characterized in that the amount of pushing inwardly can be adjusted by a tightening band that engages with the radially outer end and a single adjusting screw that can adjust the tightening amount of the tightening band. Screw device.

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