JP2000145917A - Ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a sealing property of the seal member of a ball screw. SOLUTION: A ball screw is provided with a screw shaft 11 having a ball rolling groove 11a on its outer periphery, a plurality of balls capable of rolling along the ball rolling groove 11a, a nut threadedly engaged through the balls with the screw shaft 11, and a seal member 21 provided at the shaft end of the nut. The inner periphery of the seal member 21 is provided with a spirally projected part 211 engaging with the ball rolling groove 11a. Part of the seal member 21 is peripherally split into a plurality of blocks by a plurality of slits extended to the midway of the seal member 21 from its one side 212. Some blocks are formed so that the inner peripheral edge 214c of the end face 214a may come into contact with the ball rolling groove 11a only. The other blocks are formed so that the inner peripheral edge 214c of the end face 214a may come into contact with the outer peripheral face 11b of the screw shaft 11 only.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw having a nut provided with a seal member at an end of a shaft.

[0002]

2. Description of the Related Art A seal device is mounted on a nut of a ball screw to prevent foreign matter from entering and leakage of a lubricant filled in the nut. There are various types of sealing devices. As an example, a ring-shaped sealing member provided with a helical projection fitted into a ball rolling groove of a screw shaft is attached to a shaft end of a nut. Has been put to practical use. However, there is a dimensional error between the screw shaft or its ball rolling groove and the seal member, and it is difficult to make the inner circumference of the ring-shaped seal member completely adhere to the screw shaft over the entire circumference.

In order to solve such a problem, Japanese Utility Model Application Laid-Open No.
Japanese Patent Application Laid-Open No. 80947/1990 discloses that the entire ring-shaped seal member is divided into a plurality of blocks in the circumferential direction, and some of the divided blocks are provided with projections that fit into ball rolling grooves, and other blocks are provided with other blocks. Discloses an attempt to completely seal the screw groove and the outer periphery of the screw shaft as a whole by providing a cylindrical portion in contact with the outer periphery of the screw shaft.

[0004]

However, in the device described in the above-mentioned publication, the seal member is divided over its entire length in the axial direction, and the divided blocks are pressed against the screw shaft independently of each other. . In such a completely separated type configuration, if there is a gap between the blocks in the circumferential direction of the screw shaft, foreign matter may enter the nut through the gap or lubricant may leak out of the nut. is there. However, when the blocks are brought into contact with each other so that no gap is formed between them, the movement of each block inward in the radial direction is restricted due to the contact. Therefore,
In order to ensure that the inner circumference of each block is pressed against the screw shaft and at the same time that no gap is formed between the blocks, it is necessary to machine each block with extremely high precision.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a ball screw having a sealing member capable of easily improving the sealing performance as compared with the related art.

[0006]

Hereinafter, the present invention will be described. In addition, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated embodiment.

According to a first aspect of the present invention, there is provided a screw shaft (11) having a ball rolling groove (11a) on an outer periphery, a plurality of balls (12... 12) capable of rolling along the ball rolling groove,
A nut (13) screwed to the screw shaft via the plurality of balls; and a sealing member (21) provided at a shaft end of the nut, wherein the ball rolling is provided on an inner periphery of the sealing member. In a ball screw provided with a helical protrusion (211) fitted into a groove, a part of the seal member (21) is formed from one side surface (212) facing outward in the axial direction of the nut (13). A plurality of blocks (214... 214) are circumferentially divided by a plurality of slits (213... 213) extending to the middle of the sealing member, and at least one of the plurality of blocks is in contact with the screw shaft at another position. The above-mentioned problem is solved by a ball screw characterized in that the contact position of the block with respect to the screw shaft is different.

According to the present invention, since the slit is limited to the middle of the seal member and the plurality of blocks are connected to each other on one side, the plurality of blocks are kept separated from each other in the circumferential direction. It can be pushed inward in the radial direction of the screw shaft to completely adhere to the screw shaft. In addition, since the contact positions with respect to the screw shaft are different among the plurality of blocks, the function performed by each block with respect to the seal changes between the blocks. Therefore, it is not necessary to form all the blocks uniformly with respect to the screw shaft, and complete sealing performance can be obtained as a whole by integrating the roles played by the blocks.
Since the slit is limited in the middle of the seal member, there is no possibility that foreign matter or lubricant may enter or leave the nut through the slit. There is no need to process the seal member with high precision.

In the present invention, for example, each of the plurality of blocks (214... 214) is moved with respect to the screw shaft when the screw shaft (11) is fed into the nut (13). An inner peripheral edge (214c) of one end surface (214a) oriented in the rotation direction (arrow F direction) of the nut is formed so as to contact the screw shaft, and the inner peripheral edge of the at least one block is the ball. The other block may contact only the outer peripheral surface (11b) of the screw shaft, while contacting only with the rolling groove (11a). With this configuration, foreign matter adhering to the outer peripheral surface of the screw shaft fed into the nut or the ball rolling groove can be reliably scraped off at the end surface of the block.

[0010]

FIG. 1 shows a first embodiment of a ball screw to which the present invention is applied. As is well known, the ball screw 10 includes a screw shaft 11, a number of balls 12,
And a nut 13 mounted on the screw shaft 11 via the balls 12. A ball rolling groove 13a is formed in the center hole 13c of the nut 13 (see FIG. 4).
The ball 12 rolls between the ball rolling groove 11a of the screw shaft 11 and the ball rolling groove 13a of the nut 13 with the relative rotation of the screw shaft 11 and the nut 13. Ball rolling groove 1
The ball 12 that has reached one end of 3a is returned to the opposite side of the ball rolling groove 13a via a return tube 14 fixed to a nut 13.

As shown in FIG. 2 to FIG.
Are formed at both ends thereof with wiper mounting holes 13b. Each wiper mounting hole 13b has a wiper ring 2
0 is attached and is stopped by the retaining ring 15. Each wiper ring 20 functions as a sealing device for preventing foreign matter adhering to the screw shaft 11 from entering the nut 13 and preventing a lubricant (eg, grease) filled in the nut 13 from leaking outside.

As shown in FIGS. 5 to 7, each wiper ring 20 has a ring-shaped seal member 21 and two wipers which are mounted in grooves 210, 210 on the outer periphery thereof and tighten the seal member 21 to the center side. Spring rings 22 and 22 are provided. The seal member 21 is manufactured by injection molding or cutting a synthetic resin, and has a spiral projection 211 fitted on the ball rolling groove 11a on the inner periphery thereof.

The seal member 21 is formed with a plurality of slits 213... 213 extending from one side surface 212 to an intermediate position along the axial direction at regular intervals in the circumferential direction. The slits 213 divide a part of the seal member 21 into a plurality of blocks 214... 214 in the circumferential direction. Although the number of the slits 213 and the number of the blocks 214 are six in the figure, the number may be changed as appropriate.

As shown in FIG. 5, each block 214 has a pair of end surfaces 214a and 214b in the circumferential direction. When the screw shaft 11 is fed into the nut 13, one end surface 214 a of the nut 13 with respect to the rotation direction of the nut 13 with respect to the screw shaft 11 (the direction of arrow F in FIGS. 1, 2, 5, 7, and 8) is The nut 13 is inclined so as to be gradually displaced in the radial direction of the nut 13 in the direction opposite to the forward rotation direction from the inner peripheral side toward the outer peripheral side. Hereinafter, the rotation direction of the nut 13 indicated by the arrow F is referred to as a forward rotation direction, and one end surface 214a is referred to as a front end surface.

Each block 21 facing the front end surface 214a
4, the other end surface (hereinafter, referred to as a rear end surface) 214b
The nut 13 is inclined so as to be gradually displaced in the forward rotation direction with respect to the radial direction of the nut 13 from the inner peripheral side toward the outer peripheral side. Thereby, the width of the slit 213 gradually increases toward the outer peripheral side. The radial direction of the nut 13 is equal to the direction of the auxiliary dimension lines L1 and L2 passing through the center of the seal member 21. Note that the inclination angle φ2 of the rear end surface 214b may be 0 °. That is, the rear end surface 214b may be a flat surface extending in the radial direction of the nut 13.

As is apparent from FIG. 8, the front end surface 214a
Is the ball rolling groove 11 in the direction of the axis X of the nut 13.
a is inclined in the twisting direction. That is, when the ball rolling groove 11a is inclined at a lead angle α in a predetermined twist direction D with respect to a direction (direction of the auxiliary line C) orthogonal to the axial direction of the nut 13, the front end surface 214a is oriented in the axial direction of the nut 13. On the other hand, it is inclined by a predetermined angle θ1 in the same direction as the torsional direction D. The inclination angle θ1 is set to be equal to or larger than the lead angle α. In order to positively discharge the foreign matter on the screw shaft 11 scraped off by the front end surface 214a to the outside in the axial direction of the nut 13, the inclination angle θ1 is desirably set to be larger than the lead angle α.

On the other hand, the rear end surface 214b is
It is inclined by a predetermined angle θ2 in a direction opposite to the twisting direction D with respect to a direction orthogonal to the center line E of 1a (direction of the auxiliary line G). The inclination angle θ2 is desirably set equal to or greater than the lead angle α. When the inclination angle θ2 is equal to the lead angle α, the rear end surface 214b is
Is parallel to the axial direction of When the inclination angle θ2 is set to be equal to or larger than the lead angle α, as shown in FIG.
To a pair of dies 100, 10
No undercut occurs in the slit 213 when the injection molding is performed using No. 1. As a result, the number of parts of the mold is reduced, and the labor required for injection molding is reduced, thereby achieving cost reduction.

As can be seen from FIG. 4, the wiper ring 20 has a
3 is attached to the nut 13 so as to face outward in the axial direction. FIG. 9 shows a contact state between the wiper ring 20 attached to the nut 13 and the screw shaft 11. Each block 214 is pressed against the screw shaft 11 by the pressing force of the spring rings 22 mounted on the outer periphery of the seal member 21. The contact state between the seal member 21 and the screw shaft 11 differs depending on the block 214. That is, FIG.
As shown in the figure, some of the blocks 214
At a portion where the inner peripheral edge 214c of the protrusion 14a intersects with the protrusion 211, the ball contact is made only with the ball rolling groove 11a and the screw shaft 11
Does not come into contact with the outer peripheral surface 11b. As shown in FIG. 10B, the inner peripheral edge 214c of the end surface 214a of the remaining block 214 contacts only the outer peripheral surface 11b of the screw shaft 11, and does not contact the ball rolling groove 11a. In order to provide such a change in the contact position, for example, the curvature of the inner circumference of each block 214 and the size of the protrusion 211 may be changed for each block 214. Those contacting the ball rolling grooves 11a and those contacting the screw shaft outer peripheral surface 11b may be arranged alternately in the circumferential direction or may be arranged randomly. However,
A block 214 in which a cylindrical surface portion facing the outer peripheral surface of the screw shaft 11 remains on both sides of the protrusion 211, in other words, the protrusion 2
It is preferable that the block 214 in which a part of 11 is not notched is preferentially brought into contact with the ball rolling groove 11a.

The wiper ring 2 configured as described above
According to 0, since the slit 213 is limited to the middle of the seal member 21 and the plurality of blocks 214 are connected to each other on one side, the plurality of blocks 21
4 can be pushed inward in the radial direction of the screw shaft 11 while being spaced apart from each other in the circumferential direction, and can be completely adhered to the screw shaft 11. Since each block 214 is divided into one that contacts the ball rolling groove 11a of the screw shaft 11 and one that contacts the outer peripheral surface 11b of the screw shaft 11, there is a dimensional error in the seal member 21 and the screw shaft 11. Even so, each block 214 can be reliably brought into contact with a target portion of the screw shaft 11, and there is no need to process the seal member with high precision. Since the slit 214 is limited to a point in the middle of the seal member, there is no possibility that foreign matter or lubricant may enter or leave the nut 13 through the slit 214.

Moreover, since each block 214 is formed in a trapezoidal shape with the inner side as the bottom when viewed from the axial direction of the nut 13 (see FIG. 5), the spring ring 22 causes each block 214 to move toward the center of the nut 13. Can be reliably received between the screw shaft 11 and the inner periphery of each block 214. Therefore, the front end surface 214 of the block 214
No force is generated so that the inner peripheral edge 214c of a is lifted from the screw shaft 11. Accordingly, the inner peripheral edge 2 of the front end surface 214a, which is the most important in scraping foreign matter adhered to the screw shaft 11, is formed.
14c can be reliably pressed against the screw shaft 11.

FIGS. 12 to 14 show a second embodiment of the present invention.
3 shows a ball screw according to an embodiment of the present invention. In these drawings, the same reference numerals are given to portions common to the ball screws in FIGS. 1 to 11.

As is clear from comparison with FIG. 1, FIG.
In the ball screw of FIG.
The shape of the slits 213A... 213A provided in 1A is different from that of the seal member 21 in FIG. That is, as shown in detail in FIGS. 13 and 14, in the present embodiment, the end surfaces 214 of the blocks 214A, 214A opposed to each other across the slit 213A of the seal member 21A.
a and 214b are formed substantially parallel to each other. As a result, the slit 213A is formed to have a constant width in both the radial direction and the axial direction of the nut 13. Also in this embodiment, the end surface 214a is inclined with respect to the axial direction of the screw shaft 11 in the twisting direction of the screw groove 11a (see FIG. 12) at an angle θ1 equal to or larger than the lead angle. Further, also in the radial direction of the screw shaft 11, the end surface 214a is rotated in the forward rotation direction from the inner peripheral side to the outer peripheral side (arrow F in FIG. 13).
Direction) at a predetermined angle φ1.

A protrusion 211 is formed on the inner periphery of the seal member 21A so as to fit into the ball rolling groove 11a. The contact state between the sealing member 21A and the screw shaft 11 is indicated by a block 214.
A. That is, some blocks 214
A is the inner peripheral edge 214c of the end surface 214a and the protrusion 211
At the intersection with the ball rolling groove 11a, but not with the outer peripheral surface 11b of the screw shaft 11. The remaining block 214A is an inner peripheral edge 214 of the end surface 214a.
c contacts only the outer peripheral surface 11b of the screw shaft 11, but does not contact the ball rolling groove 11a. This point is described in FIG.
(A) and (b) are the same as those in the first embodiment, and the forming method and arrangement may be the same as those in the first embodiment.

The present invention is not limited to the above-described embodiment, but may be implemented in different forms. For example, the end faces of the divided blocks do not necessarily need to be inclined with respect to the radial direction or axial direction of the screw shaft 11.

[0025]

As described above, according to the ball screw of the present invention, the slit of the seal member is limited to a point in the middle of the seal member to prevent foreign matters and lubricant from entering and exiting through the slit, and the slit is formed. In order to be able to push in the radial inside of the screw shaft while leaving the plurality of blocks divided by the circumferential direction, and to change the contact position with the screw shaft between the plurality of blocks, the desired position of each block is changed. Complete sealing performance can be obtained for the entire sealing member by bringing the sealing member into complete contact with the screw shaft. Moreover, it is not necessary to process the sealing member with high precision, and a predetermined sealing performance can be obtained with relatively simple processing.

[Brief description of the drawings]

FIG. 1 is a perspective view of a ball screw to which the present invention is applied.

FIG. 2 is a side view of the ball screw in FIG. 1 as viewed from the axial direction.

FIG. 3 is a plan view of a nut provided on the ball screw of FIG. 1;

FIG. 4 is an axial sectional view of the nut of FIG. 3;

FIG. 5 is a front view of a wiper ring attached to a shaft end of the nut of FIG. 3;

FIG. 6 is a sectional view taken along the line VI-VI of FIG. 5;

FIG. 7 is a top view of the wiper ring of FIG. 5;

FIG. 8 is an enlarged view of a slit portion provided in the wiper ring of FIG. 5 from an outer peripheral side thereof.

FIG. 9 is a view showing a state where the wiper ring of FIG. 5 is mounted on a screw shaft.

10 is a diagram showing a contact state between a block provided on a seal member of the wiper ring in FIG. 5 and a screw shaft.

FIG. 11 is a view showing a configuration for injection molding a seal member provided on the wiper ring of FIG. 5;

FIG. 12 is a perspective view of another ball screw to which the present invention is applied.

FIG. 13 is a front view of a wiper ring attached to a shaft end of a nut of the ball screw of FIG. 12;

FIG. 14 is a top view of the wiper ring of FIG. 13;

[Explanation of symbols]

 Reference Signs List 10 Ball screw 11 Screw shaft 11a Ball rolling groove 11b Outer peripheral surface of screw shaft 12 Ball 13 Nut 13a Nut ball rolling groove 13b Wiper mounting hole 14 Return tube 15, 15 Retaining ring 20 Wiper ring 21, 21A Seal member 22 Spring Ring 211 Projecting portion of seal member 212 Side surface of seal member facing outward in the nut axis direction 213, 213A Slit 214, 214A Block 214a Block front end surface (one end surface) 214b Block rear end surface (other end surface) 214c Block end surface Inner periphery

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Niwa 3-11-6 Nishi-Gotanda, Shinagawa-ku, Tokyo TEK Corporation (72) Inventor Mitsuaki Homma 3-11-6 Nishi-Gotanda, Shinagawa-ku, Tokyo Within TK Corporation

Claims (2)

[Claims] 1. A screw shaft having a ball rolling groove on an outer periphery,
A plurality of balls that can roll along the ball rolling groove,
A nut screwed to the screw shaft via the plurality of balls, and a seal member provided at a shaft end of the nut, and a spiral fit in the ball rolling groove on an inner periphery of the seal member. In a ball screw provided with a protruding portion, a part of the seal member is divided into a plurality of blocks in a circumferential direction by a plurality of slits extending from one side surface facing outward in the axial direction of the nut to a middle of the seal member. And
A ball screw, wherein a contact position of at least one block of the plurality of blocks with respect to the screw shaft is different from a contact position of another block with the screw shaft. 2. Each of the plurality of blocks is in contact with the screw shaft at an inner peripheral edge of one end face of the nut that is oriented in a rotation direction of the nut with respect to the screw shaft when the screw shaft is fed into the nut. The inner peripheral edge of the at least one block contacts only the ball rolling groove, and the inner peripheral edge of the other block contacts only the outer peripheral surface of the screw shaft. Item 2. The ball screw according to Item 1.