JP2017129187A - Seal for ball screw and ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow a seal that is fixed to an axial end part of a nut and includes a cylindrical body with an inner peripheral surface facing an outer peripheral surface of a screw shaft to be attached to the nut by a simple method.SOLUTION: The seal 4 has a projection 43 projecting in a radial direction from an outer peripheral surface of the cylindrical body 41. The projection 43 is fitted to a peripheral groove 23 formed at an inner peripheral surface of the nut 2. A retaining ring 5 is disposed at an inner peripheral surface 41a of a part where the projection 43 of the cylindrical body 41 is formed so that the retaining ring 5 presses the cylindrical body 41 on an outer side in a radial direction.SELECTED DRAWING: Figure 2

Description

  The present invention is arranged between a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a raceway formed by the spiral groove of the nut and the spiral groove of the screw shaft. The present invention relates to a seal used for a ball screw having a ball.

The ball screw is arranged between a nut having a spiral groove formed on the inner peripheral surface, a screw shaft having a spiral groove formed on the outer peripheral surface, and a track formed by the spiral groove of the nut and the spiral groove of the screw shaft. This is a device in which the nut moves relative to the screw shaft as the ball rolls in the track, preventing entry of foreign matter into the nut and outflow of lubricant from the nut. For this purpose, ring-shaped seals are arranged at both ends or one end in the axial direction of the nut.
Examples of the structure for attaching the seal to the nut in the ball screw include those described in Patent Documents 1 to 3.

  Patent Document 1 includes a solid lubricating composition containing a lubricating oil as a component that encloses a lubricating grease inside a nut and that does not cause a decrease in lubricity due to the same type or interaction with the base oil of the lubricating grease. It is described that a ring-shaped sealing member whose inner periphery is in sliding contact with the thread groove surface of the screw shaft is described. Further, after the seal member divided into four in the circumferential direction is placed in the seal mounting grooves formed at both axial ends of the nut by fitting garter springs into the grooves provided on the outer peripheral surface of each divided body, the seal member And fixing with a seal presser having four pressing portions corresponding to the respective divided portions.

Patent Document 2 describes a substantially annular contact seal in which an outer peripheral portion is attached to a nut and an inner peripheral portion is slidably contacted with a screw shaft. This seal is cut at one place in the circumferential direction, has a substantially C-shaped cross section, and has elasticity that allows the slit formed by cutting to be opened and closed, so that the seal can be displaced in the radial direction. It is described that a gap is provided between the portion and the inner peripheral surface of the nut and attached to the nut.
In Patent Document 3, a seal having a seal ridge that surrounds the outer periphery of the screw shaft and enters the screw groove of the screw shaft on the inside, and a cylindrical portion that is attached to the end of the nut and is exposed to the outside in the axial direction of the nut. Is described. In this seal, an outward flange formed at one axial end of the cylindrical portion is disposed in a recess formed on the axial end surface of the nut. When attached to the nut, the entire outer peripheral surface of the outward flange of the seal is in contact with the inner peripheral surface of the nut.

Japanese Patent Laid-Open No. 11-166608 JP 2012-159121 A JP 2013-249887 A

The seals described in Patent Documents 1 to 3 have room for improvement in that they are securely attached to the nut by a simple method.
An object of the present invention is to make it possible to securely attach a seal having a cylindrical body fixed to an axial end portion of a nut and having an inner peripheral surface facing an outer peripheral surface of a screw shaft to a nut by a simple method. That is.

In order to solve the above problems, a first aspect of the present invention provides a ball screw having the following configurations (a) to (c).
(a) a screw shaft having a spiral groove formed on the outer peripheral surface; a nut having a spiral groove formed on the inner peripheral surface; and a track formed by the spiral groove of the screw shaft and the spiral groove of the nut. A plurality of balls disposed between them, and a seal including a cylindrical body fixed to an axial end of the nut and having an inner peripheral surface facing the outer peripheral surface of the screw shaft.
(b) A circumferential groove (a groove formed in the entire circumferential direction) is formed on the inner circumferential surface of the axial end portion of the nut. The seal has a protrusion protruding in a radial direction from the outer peripheral surface of the cylindrical body, and the protrusion is fitted in the peripheral groove.
(c) A retaining ring is disposed on the inner peripheral surface of the portion of the cylindrical body where the protrusion is formed, and the retaining ring presses the cylindrical body outward in the radial direction.

A second aspect of the present invention is a ball screw having the above configurations (a) to (c) and the following configurations (d) to (f).
(d) The cylindrical body is a first cylindrical portion disposed inside the nut, and is formed integrally with the first cylindrical portion and disposed outside the nut in the axial direction, and the spiral groove of the screw shaft A second cylindrical portion having a smaller outer diameter than the first cylindrical portion, and a flange portion that forms a boundary between the first cylindrical portion and the second cylindrical portion. The protrusion is formed on the first cylindrical portion.
(e) A through hole extending in the axial direction is formed in the flange portion.
(f) The first cylindrical portion is arranged inside the nut, the second cylindrical portion is arranged outside the nut in the axial direction, and the lip portion is in the spiral groove of the screw shaft.

A third aspect of the present invention is a ball screw seal constituting the ball screw of the second aspect, and has the following constitutions (g) to (j).
(g) a screw shaft having a spiral groove formed on the outer peripheral surface, a nut having a spiral groove formed on the inner peripheral surface, and a track formed by the spiral groove of the screw shaft and the spiral groove of the nut. A ball screw having a plurality of balls disposed between them, a seal having a cylindrical body fixed to an axial end of the nut and having an inner peripheral surface facing the outer peripheral surface of the screw shaft.
(h) The cylindrical body is a first cylindrical portion disposed inside the nut, and is integrally formed with the first cylindrical portion and disposed outside the axial direction of the nut, and the spiral groove of the screw shaft A second cylindrical portion having a smaller outer diameter than the first cylindrical portion, and a flange portion that forms a boundary between the first cylindrical portion and the second cylindrical portion.
(i) It has a protrusion protruding radially from the outer peripheral surface of the first cylindrical portion. The protrusion has a shape that fits into a circumferential groove formed on the inner peripheral surface of the nut.
(j) A through hole extending in the axial direction is formed in the flange portion.

  According to the ball screw of the present invention, the seal provided with the cylindrical body fixed to the axial end of the nut and having the inner peripheral surface facing the outer peripheral surface of the screw shaft is securely attached to the nut by a simple method. It can be in the state.

It is a fragmentary sectional side view which shows the ball screw of 1st embodiment. It is sectional drawing explaining the relationship between the seal | sticker and nut in the ball screw of 1st embodiment. It is sectional drawing which shows the seal | sticker of 1st embodiment. It is a front view which shows the retaining ring which the ball screw of 1st embodiment has. It is sectional drawing explaining that a disk-shaped seal | sticker can be attached to the nut of FIG. 2 with a retaining ring. It is sectional drawing which shows the nut different from FIG. 2 which can attach the seal | sticker of 1st embodiment. It is sectional drawing which shows the seal | sticker of 2nd embodiment. It is a front view which shows the retaining ring which the ball screw of 2nd embodiment has. It is the front view (a) of the seal | sticker of 3rd embodiment, and its AA sectional drawing (b). It is the front view (a) of the seal | sticker of 4th embodiment, and its AA sectional drawing (b). It is a front view which shows the example of the seal | sticker which has a discontinuous protrusion at equal intervals. It is a front view which shows the ball screw which has a seal | sticker of 5th embodiment. It is a partial cross section side view which shows the ball screw of FIG.

  Hereinafter, although embodiment of this invention is described, this invention is not limited to embodiment shown below. In the embodiment described below, a technically preferable limitation is made for carrying out the present invention, but this limitation is not an essential requirement of the present invention.

[First embodiment]
A ball screw 10 shown in FIG. 1 includes a screw shaft 1, a nut 2, a plurality of balls 3, a seal 4, and a retaining ring 5. A spiral groove 11 is formed on the outer peripheral surface of the screw shaft 1. A spiral groove 21 is formed on the inner peripheral surface of the nut 2. The nut 2 has a flange 2B at one axial end of the cylindrical body 2A. A ball 3 is disposed between tracks formed by the spiral groove 11 of the screw shaft 1 and the spiral groove 21 of the nut 2.
The nut 2 has a ball return path for returning the ball 3 from the end point of the track to the start point. A ball 3 is also disposed in this ball return path. As the ball 3 rolls in the track in a loaded state, the nut 2 moves relative to the screw shaft 1, and the ball 3 circulates in a circulation path constituted by the ball return and the track.

As shown in FIG. 2, the inner peripheral surfaces 22 at both axial ends of the nut 2 are formed to have a diameter larger than the axial central portion where the spiral groove 21 is formed. A circumferential groove 23 is formed on the inner circumferential surface 22. The circumferential groove 23 has a tapered surface (inclined surface) 23 a that is reduced in diameter toward the inner circumferential surface 22 on the axial end portion side of the nut 2. The inclination angle θ23 of the tapered surface 23a with respect to the radial direction of the nut 2 is 30 °.
As shown in FIGS. 2 and 3, the seal 4 of the first embodiment includes a first cylindrical portion 41 disposed inside the nut 2 and a second cylindrical portion 42 disposed outside the nut 2 in the axial direction. Have. The outer diameter D41 of the first cylindrical portion 41 is slightly smaller than the diameter D22 of the inner peripheral surface 22 of the nut 2. The outer diameter D42 of the second cylindrical portion 42 is smaller than the outer diameter D41 of the first cylindrical portion 41 and slightly larger than the outer diameter of the screw shaft 1. The first cylindrical portion 41 and the second cylindrical portion 42 are integrally formed with the central axis aligned.

A protrusion 43 protruding in the radial direction from the outer peripheral surface of the first cylindrical portion 41 is formed at an end portion on the side away from the second cylindrical portion 42 in the axial direction of the first cylindrical portion 41. The protrusion 43 is continuously formed over the entire circumference of the first cylindrical portion 41. The dimension J43 along the axial direction of the first cylindrical portion 41 of the protrusion 43 is slightly larger than the axial dimension J23 of the nut 2 of the circumferential groove. The cross-sectional shape of the projection 43 obtained by cutting the seal 4 along the diameter of the first cylindrical portion 41 is a mountain shape, and the projection 43 is formed on the first inclined surface 43 a on the second cylindrical portion 42 side and on the opening side of the first cylindrical portion 41. It has the 2nd slope 43b.
That is, the surface of the protrusion 43 on the second cylindrical portion 42 side in the axial direction of the first cylindrical portion 41 is a first inclined surface 43 a inclined with respect to the radial direction of the first cylindrical portion 41. An angle θ1 between the radial direction of the first cylindrical portion 41 and the first inclined surface 43a is 30 °, which is the same as the inclination angle θ23 of the tapered surface 23a of the nut 2. The angle θ1 is preferably 8 ° or more. An angle θ2 between the radial direction of the first cylindrical portion 41 and the second inclined surface 43b is 34 °. The angle θ2 is preferably 45 ° or more from the viewpoint of easy insertion of the seal 4 into the nut 2.

As shown in FIG. 3, in the axial direction of the first cylindrical portion 41, the inner diameter d411 of the portion where the protrusion 43 is formed is slightly larger than the inner diameter d41 of the portion where the protrusion 43 is not formed. Further, the inner diameters d41 and d411 of the first cylindrical portion 41 are larger than the inner diameter d42 of the second cylindrical portion 42. The retaining ring 5 is disposed on the inner peripheral surface (inner peripheral surface of the protrusion position) 41 a of the portion where the protrusion 43 is formed in the axial direction of the first cylindrical portion 41. In other words, the inner diameter of the first cylindrical portion 41 is formed larger than the other portions at the protruding position that becomes the installation surface of the retaining ring 5.
A lip portion 42 a that enters the spiral groove 11 of the screw shaft 1 is formed on the inner peripheral surface of the second cylindrical portion 42. The lip portion 42 a has an inner peripheral edge shape similar to the cross-sectional shape perpendicular to the axis of the screw shaft 1.

A protrusion 44 a that protrudes outward from the outer peripheral surface of the first cylindrical portion 41 is formed on the flange portion 44 that forms the boundary between the first cylindrical portion 41 and the second cylindrical portion 42. The protrusion 44 a of the flange portion 44 is also formed continuously over the entire circumference of the first cylindrical portion 41 and the second cylindrical portion 42. The outer diameter of the protrusion 44 a of the flange portion 44 is the same as the outer diameter of the protrusion 43 of the first cylindrical portion 41.
The seal 4 is made of a synthetic resin and is preferably manufactured by injection molding. Examples of the synthetic resin that can be used include polyoxymethylene (POM).

The retaining ring 5 is a C-shaped retaining ring as shown in FIG. 4 and has a rectangular cross-sectional shape as shown in FIGS. 1 and 2. The material of the retaining ring 5 is metal.
The ball screw 10 is assembled as follows.
First, after inserting the screw shaft 1 into the nut 2, the ball is inserted into the track from the ball return path. Next, in a state where the screw shaft 1 and the nut 2 are fixed with a jig, the seal 4 in which the retaining ring 5 is fitted to the inner peripheral surface 41a at the protruding position of the first cylindrical portion 41 is screwed from the first cylindrical portion 41 side. Fit on shaft 1. Next, the first cylindrical portion 41 is pushed into the opening at the axial end portion of the nut 2.

When the first cylindrical portion 41 of the seal 4 is pushed into the opening of the nut 2, the protrusion 43 enters the circumferential groove 23 after passing through the inner peripheral surface 22 while being elastically deformed and contracted, and the axial direction of the nut 2. The first inclined surface 43 a of the protrusion 43 is pressed against the tapered surface 23 a of the circumferential groove 23. The retaining ring 5 is deformed following the deformation of the protrusion 43, and then presses the inner peripheral surface 41a at the protrusion position of the first cylindrical portion 41 radially outward.
The first cylindrical portion 41 is disposed in the inner peripheral surface 22 of the nut 2 except for the boundary portion with the second cylindrical portion 42, and there is a gap between the inner peripheral surface 22 and the first cylindrical portion 41. There are no or slight gaps. A flange portion 44 that forms a boundary between the second cylindrical portion 42 and the second cylindrical portion 42 of the first cylindrical portion 41 is disposed outside the nut 2. The protrusion 44 a of the flange portion 44 opposes the axial end surface of the nut 2. The lip portion 42 a of the second cylindrical portion 42 enters the spiral groove 11 of the screw shaft 1.

As described above, according to the seal 4 of the first embodiment, a nut can be easily obtained by pressing the first cylindrical portion 41 into the axial end of the nut 2 while the nut 2 is fixed with a jig or the like. 2 can be attached. Moreover, since the 1st slope 43a of the protrusion 43 presses against the taper surface 23a of the circumferential groove 23, the attachment state with respect to the circumferential groove of a nut is stabilized compared with the seal which cannot make such a surface contact.
By the way, the temperature of the ball screw greatly rises due to heat generation during driving, and the temperature of the ball screw changes due to the temperature change of the installation environment. Since the seal 4 made of synthetic resin has a larger linear expansion coefficient than the nut 2 made of metal, the seal 4 expands more than the nut 2 when the temperature of the ball screw rises. Strength increases.

When the seal 4 creep-deforms in this state, only the nut 2 returns to its original dimension when the temperature is lowered. Therefore, the first cylindrical portion 41 and the protrusion 43 of the seal 4, the inner peripheral surface 22 of the nut 2 and the peripheral groove A slack occurs between the two. When the drive of the ball screw continues in this state and the seal 4 rotates with respect to the nut 2, a phenomenon occurs in which the lip portions 42 a of the two seals 4 are tightened into the spiral groove 11 of the screw shaft 1. There is a problem that 4 strongly contacts the screw shaft 1.
On the other hand, in the ball screw 10 of the first embodiment, since the retaining ring 5 presses the protrusion 43 of the seal 4, even when creep deformation occurs in the seal 4, the protrusion 43 of the seal 4 and the nut 2 It is possible to prevent loosening between the circumferential groove 23 and the circumferential groove 23. As a result, in the ball screw 10 of the first embodiment, the above-described problems are solved and the seal 4 is securely attached.

In addition, since the inner peripheral surface 41a at the protruding position of the first cylindrical portion 41 has a larger diameter than other portions and the retaining ring 5 is installed at this position, the retaining ring 5 is displaced from the projecting position of the seal 4. Is prevented. Thereby, the pressing action of the protrusion 43 by the retaining ring 5 is reliably exhibited.
In addition, as shown in FIG. 5, the disc-shaped seal 6 can be fixed to the circumferential groove 23 of the nut 2 using a retaining ring 50. That is, the seal 4 of the first embodiment can be attached to a nut to which the disc-shaped seal 6 is fixed using the retaining ring 50. Therefore, either the seal 4 or the disc-shaped seal 6 of the first embodiment can be selected and attached to the nut 2 having the circumferential groove 23 in accordance with the use of the ball screw.
Moreover, the phase of the seal 4 can be adjusted by rotating the seal 4 relative to the screw shaft 1 at the time of attachment.
As shown in FIG. 6, the seal 4 of the first embodiment can be attached to the nut 20 in which the circumferential groove 23 does not have an inclined surface.

[Second Embodiment]
As shown in FIG. 7, the seal 4 </ b> A of the second embodiment is formed with a protrusion 43 </ b> A having a cross-sectional shape different from that of the seal 4 of the first embodiment. The cross-sectional shape cut along the diameter of the first cylindrical portion 41 of the protrusion 43A is an arc shape. That is, the protrusion 43A has an arc-shaped protruding surface. The formation position of the protrusion 43A is an end portion on the side away from the second cylindrical portion 42 in the axial direction of the first cylindrical portion 41, but is a position slightly closer to the second cylindrical portion 42 side than the end surface.
A circumferential groove 41b is formed on the inner circumferential surface of the portion of the first cylindrical portion 41 where the projection 43A is formed. The cross-sectional shape of the circumferential groove 41b is an arc concentric with the arc forming the protrusion 43A. Other points are the same as the seal 4 of the first embodiment. When the seal 4 </ b> A is attached, the retaining ring 5 </ b> A shown in FIG. 8 is fitted into the circumferential groove 41 b of the first cylindrical portion 41. The retaining ring 5A has a circular cross-sectional shape.
According to the seal 4A of the second embodiment, in addition to the same effect as that of the seal 4 of the first embodiment, the protrusion 43A has an arcuate projecting surface, so that it is more shaped than the seal 4 of the first embodiment. As a result, the manufacturing cost can be reduced as much as it becomes simple.

[Third embodiment]
As shown in FIG. 9, the seal 4 </ b> B of the third embodiment has a slit 46 extending in the axial direction in the first cylindrical portion 41. As a result, in the seal 4 </ b> B of the third embodiment, the protrusion 43 exists only in a portion where there is no slit 46. That is, the protrusion 43 is formed discontinuously in the circumferential direction of the first cylindrical portion 41. The points other than this are the same as the seal 4 of the first embodiment.
The slit 46 extends from the end surface opposite to the second cylindrical portion 42 in the axial direction of the first cylindrical portion 41 to the side closer to the flange portion 44 than the end point position L of the protrusion 43. The axial dimension of the first cylindrical portion 41 of the slit 46 is preferably 1.5 times or more the width (axial dimension) of the retaining ring 5.
The slits 46 are formed at four locations (a plurality of locations) in the circumferential direction of the first cylindrical portion 41. The four slits 46 are formed in a cross-sectional circle of the first cylindrical portion 41, and two slits 46 are formed at positions that are 180 ° from each other. As a result, the seal 4 </ b> B has four (plural) protrusions 431 to 434 that are formed discontinuously in the circumferential direction of the first cylindrical portion 41.

The protrusion 431 and the protrusion 433 are present at 180 ° in the cross-sectional circle of the first cylindrical portion 41. The protrusion 432 and the protrusion 434 are present at a position where the cross-section circle of the first cylindrical portion 41 is 180 °. That is, the protrusion 43 of the seal 4B includes a portion formed at a position where the cross-section circle of the first cylindrical portion 41 is 180 °. Further, the central angle γ in the cross-sectional circle of the first cylindrical portion 41 in the portion where the protrusion 43 is not present is less than 180 °.
According to the seal 4B of the third embodiment, in addition to the same effect as the effect of the seal 4 of the first embodiment, the protrusion 43 is easily deformed inside the first cylindrical portion 41 by having the slit 46. Only the effect which becomes easy to insert in the nut 2 rather than the seal 4 of 1st embodiment is also acquired.

Further, the central angles β1 to β4 of the projections 431 to 434 in the cross-sectional circle of the first cylindrical portion 41 are smaller than the central angle γ of the portion without the projection. That is, the total of the range in which the four protrusions 431 to 434 are discontinuously formed in the circumferential direction of the first cylindrical portion 41 is smaller than the total of the range in which the protrusions 431 to 434 are not formed. From the viewpoint of easy insertion into the nut 2, the total circumferential length of the plurality of protrusions 43 formed discontinuously in the circumferential direction of the first cylindrical portion (cylindrical body) 41 is 2 of the total circumferential length. / 3 or less is preferable.
In addition, when the protrusion 43 is formed discontinuously in the circumferential direction of the first cylindrical portion (cylindrical body) 41, the seal has a plurality of protrusions, but a portion having no protrusion in the cross-sectional circle of the first cylindrical portion 41 ( All the central angles γ of the interval between adjacent protrusions need to be less than 180 °. If there is a central angle γ of 180 ° or more, the function of fixing the seal nut 2 to the circumferential groove 23 of the seal 43 cannot be exhibited. In addition, as long as the central angle γ of the portion without the protrusion is less than 180 °, the circumferential dimension of the plurality of protrusions may be different.

[Fourth embodiment]
The seal 4C according to the fourth embodiment shown in FIG. 10 has three slits 46 extending in the axial direction in the first cylindrical portion 41, like the seal 4B according to the third embodiment. The first cylindrical portion 41 extends in the entire axial direction and penetrates the flange portion 44. That is, the seal 4C of the fourth embodiment has a through hole 44b that penetrates the flange portion 44 in the axial direction as a part of the slit 46A. That is, in the seal 4 </ b> C of the fourth embodiment, the through hole 44 b that penetrates the flange portion 44 in the axial direction is continuous with the slit.

When the retaining ring 5 is fitted to the inner peripheral surface 41a of the projecting position of the first cylindrical portion 41 when the ball screw 10 is assembled, if the opening 51 of the retaining ring 5 is disposed at a position without the through hole 44b, The retaining ring 5 can be seen in the ball screw 10 from the through hole 44b of the seal 4C.
The points other than these are the same as the seal 4B of the third embodiment.
According to the seal 4C of the fourth embodiment, in addition to the same effects as the effects of the seal 4B of the third embodiment, the following effects are also obtained.
That is, by providing the flange portion 44 with the through hole 44b, it is possible to confirm whether or not the retaining ring 5 is attached to the seal 4C after attaching the seal 4C to the nut 2. In addition, since the through hole 44b is continuous with the slit 46, the manufacturing cost can be reduced by the amount of simplification of the mold structure of the seal 4C, compared to the case where the through hole 44b is not continuous with the slit 46. It also has an effect.

When the retaining ring 5 is attached to the seal 4C, if the opening 51 of the retaining ring 5 and the through hole 44b of the seal 4C overlap, it cannot be confirmed whether the retaining ring 5 is attached after the seal 4C is attached to the nut 2. . Therefore, the position where there is no through hole 44b in the circumferential direction at the position where the retaining ring 5 is arranged in the axial direction of the inner peripheral surface 41a of the first cylindrical portion 41 (the position where the protrusion 433 protruding radially outward is formed). In addition, it is preferable to provide the projection 7 protruding radially inward from the inner peripheral surface 41a so that the opening 51 of the retaining ring 5 can be easily arranged at a position without the through hole 44b.
Further, in the case of the seal having the slits 46, the number and positions of the slits 46 are not limited to the examples in FIGS. 9 and 10, and for example, at three places in the circumferential direction of the first cylindrical portion 41 as shown in FIG. The first cylindrical portion 41 may be formed at a position where the cross-sectional circle of the first cylindrical portion 41 is 120 °. As a result, the seal 4 </ b> D in FIG. 11 has three protrusions 431 to 433 formed discontinuously in the circumferential direction of the first cylindrical portion 41.

[Fifth embodiment]
As shown in FIGS. 12 and 13, the seal 4 </ b> E of the fifth embodiment has six (a plurality) slits 48 in which the second cylindrical portion 42 is inclined at a predetermined angle α with respect to the axial direction. Moreover, the flange part 44 which makes the boundary with the 2nd cylindrical part 42 of the 1st cylindrical part 41 is formed thicker than another part. A through hole 44 b extending in the axial direction is formed in the flange portion 44.
Further, when the ball screw 10 is assembled, when the retaining ring 5 is fitted to the inner peripheral surface 41a at the protruding position of the first cylindrical portion 41, the opening of the retaining ring 5 is disposed at a position without the through hole 44b. The retaining ring 5 can be seen from the through-hole 44b of the seal 4E on the ball screw 10 of FIG.

Other points are the same as the seal 4 of the first embodiment.
Each slit 48 extends from the end surface 42 b of the second cylindrical portion 42 on the side opposite to the first cylindrical portion 41 to a position just before the boundary with the first cylindrical portion 41. The screw shaft 1 of the ball screw 100 is a right-hand thread, and the inclination direction of each slit 48 when viewed from the end face 42b of the second cylindrical portion 42 is a counterclockwise direction. Since the seal 4E has such a slit 48, the following action can be exhibited.
That is, when the grease on the inner side of the nut 2 is going to be taken out while adhering to the screw shaft 1, the grease is the edge portion of the slit 48 of the seal 4E (the corner portion existing in the direction in which the slit extends). Is scraped off and is scraped off along the slit 48 onto the end face 42 b of the second cylindrical portion 42. As a result, excess grease inside the nut 2 is taken out to the outside at a position where the centrifugal force of the screw shaft 1 is difficult to act, so that it is prevented from scattering around.

In addition, by providing the through hole 44 b in the flange portion 44, it is possible to confirm whether or not the retaining ring 5 is attached to the seal 4 after attaching the seal 4 to the nut 2.
That is, according to the seal 4E of the fifth embodiment, in addition to the same effect as that of the seal 4 of the first embodiment, the above-described effect by having the slit 48 and the through hole 44b in the flange portion 44 are provided. The above-mentioned effect by this is also acquired.

DESCRIPTION OF SYMBOLS 1 Screw shaft 11 Spiral groove of screw shaft 2 Nut 21 Helical groove of nut 2A Nut cylindrical body 2B Flange of nut 22 Inner peripheral surface of both axial ends of nut 23 Circumferential groove 23a Tapered surface (inclined surface) of peripheral groove
3 Ball 4 Seal 4A Seal 4B Seal 4C Seal 4D Seal 4E Seal 41 First cylindrical part (cylindrical body)
41a Inner circumferential surface of the projection position of the first cylindrical portion 41b Circumferential groove having an arc-shaped cross section 42 Second cylindrical portion 42a Lip portion 42b End surface of the second cylindrical portion 43 Projection 43A Projection 43a First slope of projection 43b Second projection Slope 431-434 Protrusion 44 Flange part 44a Flange part protrusion 44b Flange part through hole 46 Slit 46A Slit continuous to the through hole 48 Slit 5 Retaining ring 50 Retaining ring 51 Retaining ring opening 6 Disc-shaped seal 7 Protrusion 10 Ball screw 100 Ball screw γ Center angle in the cross-sectional circle of the cylindrical body in the part without projection

Claims (9)

A screw shaft having a spiral groove formed on the outer peripheral surface;
A nut having a spiral groove formed on the inner peripheral surface;
A plurality of balls disposed between tracks formed by the spiral groove of the screw shaft and the spiral groove of the nut;
A seal provided with a cylindrical body fixed to the axial end of the nut and having an inner peripheral surface facing the outer peripheral surface of the screw shaft;
With
A circumferential groove is formed on the inner circumferential surface of the axial end of the nut,
The seal has a protrusion protruding radially from the outer peripheral surface of the cylindrical body,
The protrusion is fitted into the circumferential groove;
A ball screw in which a retaining ring is disposed on an inner peripheral surface of a portion of the cylindrical body where the protrusion is formed, and the retaining ring presses the cylindrical body outward in the radial direction. The cylindrical body includes a first cylindrical portion disposed inside the nut, and a lip formed integrally with the first cylindrical portion and disposed outside the nut in the axial direction, and entering the spiral groove of the screw shaft. A second cylindrical part having an outer diameter smaller than the first cylindrical part, and a flange part that forms a boundary between the first cylindrical part and the second cylindrical part,
The protrusion is formed on the first cylindrical portion;
A through hole extending in the axial direction is formed in the flange portion,
The said 1st cylindrical part is arrange | positioned inside the said nut, a said 2nd cylindrical part is arrange | positioned at the axial direction outer side of the said nut, The said lip | rip part is in the said spiral groove of the said screw shaft. Ball screw. The protrusion is formed discontinuously in the circumferential direction of the first cylindrical portion by a slit extending in the axial direction from an end surface of the first cylindrical portion opposite to the second cylindrical portion, and is a portion of the portion without the protrusion. A central angle in a cross-sectional circle of the first cylindrical portion is less than 180 °,
The ball screw according to claim 2, wherein the through hole is continuous with the slit. The protrusion has a slope inclined with respect to the radial direction of the cylindrical body,
The ball screw according to any one of claims 1 to 3, wherein the circumferential groove has an inclined surface having the same inclination as the inclined surface on an axial end portion side of the nut.   The projection has an arc-shaped projecting surface, an inner circumferential surface of a portion of the cylindrical body where the projection is formed has a circumferential groove having an arc-shaped cross section, and the retaining ring fits in the circumferential groove The ball screw according to claim 1, which has a circular cross-sectional shape. Arranged between a screw shaft having a spiral groove formed on the outer peripheral surface, a nut having a spiral groove formed on the inner peripheral surface, and a track formed by the spiral groove of the screw shaft and the spiral groove of the nut. A ball screw having a plurality of balls, a seal having a cylindrical body fixed to an axial end of the nut and having an inner peripheral surface facing the outer peripheral surface of the screw shaft,
The cylindrical body includes a first cylindrical portion disposed inside the nut, and a lip formed integrally with the first cylindrical portion and disposed outside the nut in the axial direction, and entering the spiral groove of the screw shaft. A second cylindrical part having an outer diameter smaller than the first cylindrical part, and a flange part that forms a boundary between the first cylindrical part and the second cylindrical part,
A protrusion protruding radially from the outer peripheral surface of the first cylindrical portion;
The protrusion has a shape that fits into a circumferential groove formed on the inner peripheral surface of the nut,
A ball screw seal in which a through hole extending in the axial direction is formed in the flange portion. The protrusion is formed discontinuously in the circumferential direction of the first cylindrical portion by a slit extending in the axial direction from an end surface of the first cylindrical portion opposite to the second cylindrical portion, and is a portion of the portion without the protrusion. A central angle in a cross-sectional circle of the first cylindrical portion is less than 180 °,
The ball screw seal according to claim 6, wherein the through hole is continuous with the slit.   The ball screw seal according to claim 6 or 7, wherein the protrusion has a slope inclined with respect to the radial direction of the first cylindrical portion.   The ball screw according to claim 6 or 7, wherein the projection has an arc-shaped projecting surface, and an inner circumferential surface of a portion of the first cylindrical portion where the projection is formed has a circumferential groove having a circular arc-shaped cross section. seal.

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