JP2016142341A - Circulation piece and ball screw with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circulation piece having an improved operative characteristic caused by an action of a rolling member at an entrance of the circulation piece and a ball screw including the same.SOLUTION: A circulation piece 100 installed at a nut 20 of a ball screw 1 is composed of two divided segments 100A and 100B. The divided segments 100A and 100B has circulation piece main bodies 110A and 110B having return grooves 111A and 111B constituting a return passage 111, respectively and engaging segments 120A and 120B protruded from both surfaces of the circulation piece main bodies 110A and 110B and engaged with the nut 20, respectively. The circulation piece main bodies 110A and 110B are provided with a tongue part 112 for guiding the rolling member into the return passage 111, and position alignment segments 113 and 114 assembled to each other, and a diameter of the return passage 111 is 1.0 or more and 1.1 or less times of a diameter of the rolling member.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a circulating screw for a ball screw and a ball screw provided with the same.

2. Description of the Related Art Conventionally, an internal circulation type ball screw having a screw shaft, a nut, and a rolling element (for example, a ball) and provided with a circulation top for circulating a plurality of rolling elements interposed between the screw shaft and the nut. It has been known.
The technique described in Patent Document 1 is an example of this type of ball screw, and adopts a shape in which the return path of the circulating top is made into a tunnel shape and the rolling element is not brought into contact with the land portion of the screw shaft. According to the circulation top having such a structure, as a ball screw provided with a circulation top, compared to the conventional internal circulation structure in which the rolling element is circulated so as to cross over the land portion of the screw shaft to the adjacent spiral groove. It is said that the operability of can be improved.
The technique described in Patent Document 1 has a function of fixing the circulating top to the nut by a cylindrical cross-sectional element extending from the wall of the circulating top. By making such a configuration, the circulation top is fixed by restricting the outer diameter direction, the axial direction, and the rotation direction of the nut.

Japanese Examined Patent Publication No.57-33464

However, although the technique disclosed in Patent Document 1 improves the circulation function by separating the rolling elements from the screw shaft with a return path as a tunnel shape, the circulation top which is the boundary between the load area and the no-load area. There was room to improve the operability due to the behavior of the rolling elements at the doorway.
Therefore, the present invention has been made paying attention to the above problems, and its purpose is to provide a circulating top improved in operability due to the behavior of the rolling element at the entrance and exit of the circulating top and a ball screw provided with the same. There is to do.

A mode with a circulating top for achieving the above object includes a screw shaft having a spiral groove on the outer peripheral surface, and a nut having a spiral groove on the inner peripheral surface that is externally fitted to the screw shaft; A cylindrical return path used for a ball screw having a plurality of rolling elements arranged in a track formed by these spiral grooves, mounted on the nut, and for returning the rolling element to a previous track. With
A return groove for forming the return path is formed, a circulating top body formed of two divided bodies with a joining surface formed orthogonally to the return path, and a spiral of the ball screw from both sides of the divided body, respectively. And an engaging portion provided so as to protrude along the groove and limit the movement of the circulating top body,
The circulating top body is provided with a tongue for guiding the rolling elements into the return path,
The diameter of the return path is more than 1.0 times and less than 1.1 times the rolling element,
A positioning convex part and a concave part are provided on each joint surface of the divided body.

Here, in the circulation top, the return path includes a straight line for scooping up the rolling element in a direction substantially perpendicular to the scooping angle, and a straight line connecting two or more curves and curves in the return path. May be configured.
In the circulation top, the cross section of the return path may have an elliptical shape with the radial direction as the major axis.

In another aspect of the ball screw for achieving the above object, a screw shaft having a spiral spiral groove on the outer peripheral surface, and a nut having a spiral spiral groove on the inner peripheral surface by being externally fitted to the screw shaft And a plurality of rolling elements arranged in a track formed by these spiral grooves, and a circulation top having a return groove that is attached to the nut and returns the rolling element to the previous track,
The nut includes a circulation top insertion hole for mounting the circulation top, and the circulation top is inserted into the circulation top insertion hole.
A cylindrical return path for returning the rolling element to the previous track,
A return groove for forming the return path is formed, a circulating top body formed of two divided bodies with a joining surface formed orthogonally to the return path, and a spiral of the ball screw from both sides of the divided body, respectively. And an engaging portion provided so as to protrude along the groove and limit the movement of the circulating top body,
The circulating top body is provided with a tongue for guiding the rolling elements into the return path,
The diameter of the return path is more than 1.0 times and less than 1.1 times the rolling element,
A positioning convex part and a concave part are provided on each joint surface of the divided body.

Here, in the ball screw, the return path includes a straight line for scooping up the rolling element in a direction substantially orthogonal to the scooping angle, and a straight line connecting two or more curves and curves in the return path. May be configured.
In the ball screw, a cross section of the return path may have an elliptical shape with a major axis in the radial direction.

  According to the present invention, it is possible to provide a circulating top improved in operability due to the behavior of the rolling elements at the entrance and exit of the circulating top and a ball screw including the same.

It is a perspective view which shows the structure in one Embodiment of a ball screw. It is sectional drawing of the nut in one Embodiment of a ball screw. It is a figure which shows the structure in one Embodiment of a circulation top, (a) is a perspective view which shows the structure of the division body which comprises a circulation top, (b) is a top view which shows the structure of a division body. It is sectional drawing which shows the structure of the division body in one Embodiment of a circulation top, (a) is a figure explaining the structure of a return path (return groove), (b) is the A section enlarged view of (a). is there. It is sectional drawing which shows the structure of the return path of a circulation top, (a) is sectional drawing which shows the structure of the return path in other embodiment of a circulation top, (b) is the structure of the return path in one embodiment of a circulation top. FIG.

Hereinafter, an embodiment of a circulating top and a ball screw including the same will be described with reference to the drawings.
FIG. 1 is a perspective view showing a configuration of an internal circulation type ball screw according to the present embodiment. In FIG. 1, the nut 20 is shown cut along a plane including its axis. FIG. 2 is a cross-sectional view of a nut in the ball screw of this embodiment. In addition, in FIG. 2, the installation position of the circulating top is also shown in the sectional view of the nut.

(Ball screw)
As shown in FIG. 1, the ball screw 1 includes a screw shaft 10, a nut 20, and rolling elements (for example, balls) 30.
The screw shaft 10 has a spiral groove 11 having a predetermined lead formed on the outer peripheral surface 10a thereof. The nut 20 has a substantially cylindrical shape, and an inner diameter thereof is formed to be larger than an outer diameter of the screw shaft 10. The nut 20 is externally fitted to the screw shaft 10 with a predetermined gap.
The nut 20 has a flange 22 for coupling with a guide object at one end thereof. A helical spiral groove 21 having a lead equal to the lead of the screw shaft 10 is formed on the inner peripheral surface 20 a of the nut 20. The spiral groove 11 and the spiral groove 21 facing the screw shaft 10 and the nut 20 form a substantially circular cross section. A plurality of rolling elements 30 are filled in the track.

  Further, as shown in FIG. 2, a circulating top insertion hole 23 for attaching the circulating top 100 is formed in the nut 20. The circulation top insertion hole 23 is a long hole penetrating from the outer periphery to the inner periphery of the nut 20. The long hole is processed by, for example, an end mill, and is formed by inclining the end mill by a predetermined angle with respect to a line orthogonal to the center line of the nut 20. This predetermined angle is set to an angle at which the rolling element 30 that rolls in the spiral groove 11 does not change direction suddenly by a cylindrical return path (also referred to as a ball return path) 111 formed in the circulation top 100. . A plurality (for example, three) of the circulating top insertion holes 23 are machined according to the number of the circulating tops 100 at equal intervals in the circumferential direction of the nut 20.

(Circulation top)
Next, the above circulating top 100 will be described in more detail.
FIG. 3 is a diagram showing the configuration of the circulating top of the present embodiment, (a) is a perspective view showing the configuration of the divided body constituting the circulating top, and (b) is a plan view showing the configuration of the divided body. . Note that FIG. 3A shows only one of the two divided bodies (first divided body). FIG. 4 is a cross-sectional view along the circulation passage showing the configuration of the circulating top divided body of the present embodiment, and (a) is a diagram for explaining the configuration of the return path (return groove). ) Is an enlarged view of part A of (a).
The circulating top 100 is formed from, for example, a sintered alloy. As shown in FIG. 2, the circulating top 100 includes a circulating top main body 110 in which a return path 111 is formed, and two engagements provided so as to protrude from opposite sides of the circulating top main body 110 in the longitudinal direction. Parts 120 and 120.
One circulating top 100 is provided for one turn of the ball row filled in the ball screw 1. That is, since the number of turns of the rolling element 30 is determined from the load applied to the ball screw 1, the number of the circulating tops 100 is appropriately determined (for example, 3) depending on the load applied to the ball screw 1.

<Circulation top body>
As shown in FIG. 2, the circulating top main body 110 is mounted in each circulating top insertion hole 23 of the nut 20. That is, the outer shape of the circulating top body 110 is formed in alignment with the circulating top insertion hole 23 of the nut 20 described above.
A cylindrical return path 111 that connects one end of the track and the other end of the track just before the winding is formed inside the circulation top body 110. The return path 111 extends in a substantially S shape in the longitudinal direction of the circulation top main body 110 and is formed to open toward the inner peripheral side of the nut 20. This substantially S-shape is a shape determined from a function for returning the rolling elements 30. That is, the return path 111 needs to change the course of the rolling element 30 so as to return the rolling element 30 rolling on the track to the track one turn before and align with the track. Therefore, when the planar shape is a cam curve, for example, a cam curve corresponding to a modified sine curve is combined to form a substantially S-shape so as to suppress rapid fluctuations in acceleration relative to the lift. Has been.

Also, a tongue 112 for guiding the rolling element 30 into the return path 111 is provided in the vicinity of at least one opening of the return path 111 of the circulation top 100 (see FIG. 4A).
The return path 111 has a cross-section in the short direction of the circulating top main body 110 from a tongue 112 provided at both ends in the longitudinal direction of the circulating top 100 toward the longitudinal center of the circulating top main body 110. A continuous U shape having an inner diameter matched with the outer diameter of 30 is formed, and this forms a cylindrical shape (tunnel) integrally with the above-described substantially S shape.

<Engagement part>
When the circulating top 100 is mounted in the circulating top insertion hole 23 of the nut 20, the engaging portions 120 are provided so that the respective engaging portions 120, 120 protrude along the spiral groove 11. Since the engaging portions 120 and 120 are provided in this way, the engaging portions 120 and 120 extend in opposite directions and engage with the adjacent spiral grooves 11 and 11, respectively. There is an effect that it is fixed to.
As described above, the return path 111 (and the tongue 112) is provided in the circulation top 100, so that the rolling elements 30 rolling in the track toward the circulation top 100 can be efficiently moved in the radial direction of the screw shaft 10. It is possible to circulate the rolling element 30 by scooping up, overcoming the thread and returning it to the track just before one winding (one lead before). Then, a substantially circular infinite circulation path is formed outside the screw shaft 10 by the path formed by the return path 111 and the track. As a result, the rolling element 30 rolls between the spiral groove 11 and the spiral groove 21 in accordance with the relative rotation of the screw shaft 10 with respect to the nut 20, so that the nut 20 rotates relative to the screw shaft 10. 10 linear movements are possible.

[Split]
Here, as shown in FIGS. 3 (a) and 3 (b), the circulating top body 110 has two joint surfaces 101A and 101B formed so as to be orthogonal to the return path 111 formed in the circulating top 100. It consists of divided bodies 110A and 110B. Specifically, the above-described two engaging portions 120 and 120 are provided as two engaging portions 120A and 120B provided so as to protrude in opposite directions from both side surfaces of the divided bodies 110A and 110B.
In the return path 111 described above, each return groove (only one return groove 111A, see FIG. 4 (a)) formed on the joint surface side of each of the divided bodies 111A and 111B is the same as that of the divided bodies 111A and 111B. Formed by superposition. Hereinafter, the shape of the return path 111 will be described with reference to the return groove 111A in FIGS. 4 (a) and 4 (b).

As shown in FIG. 4A, the return path 111 requires that the rolling element 30 entering the return path 111 can get over the outer diameter of the screw shaft 10 and be aligned with the annular cross-sectional shape of the nut 20. is there. Therefore, the return path 111 is formed to have an arc shape that is most depressed at the center position in the longitudinal direction of the circulating top body 110 (divided body 110A).
Further, the diameter d ₁ (see FIG. 4A) of the return path 111 is set to be more than 1.0 times and less than 1.1 times that of the rolling element 30. By setting in this way, the clearance between the rolling elements 30 and the return path 111 is reduced, and so-called “plovers” in which the rolling elements are staggered and deviated from the rolling direction in the track (including the return path). Can be suppressed.

Further, as shown in FIG. 4A, two joints 101A and 101B of the divided bodies 110A and 110B are provided as alignment guides when the divided bodies 110A and 110B are overlapped. Positioning portions 113 and 114 are provided. These alignment portions 113 and 114 are provided as convex portions or concave portions having different forms on the same joint surfaces 101A and 101B, and the alignment portion 113 of the divided body 110A and the alignment portion 114 of the divided body 110B are fitted to each other. Then, the alignment portion 114 of the divided body 110A and the alignment portion 113 of the divided body 110B are fitted.
In the return path 111, as shown in FIGS. 4A and 4B, the center line w of the return path 111 is substantially orthogonal to the scooping angle θ with respect to the axis O of the screw shaft 10. the straight line L ₁ for scooping the rolling elements 30 in the direction, may be configured to be composed of the straight line L ₂ Metropolitan connecting the two or more curves C ₁ and curve C ₂ in the return path 111.

(Other embodiments)
FIG. 5 is a cross-sectional view showing the configuration of the return path of the circulation top, (a) is a cross-sectional view showing the configuration of the return path in one embodiment of the circulation top, and (b) is another embodiment of the circulation top. It is sectional drawing which shows the structure of a return path | route.
As another embodiment of the circulating top 100 and a ball screw provided with the same, as shown in FIG. 5A, the cross section of the return path 111 is more than 1.0 times the diameter d of the rolling element 30, 1.1. It may be an elliptical shape having a major axis in the radial direction (indicated by an arrow in the figure). By adopting such a configuration, the clearance δb between the rolling elements and the return path is further reduced, and the rolling elements are alternately positioned in the track (including the return path) so as to deviate from the rolling direction. Can be further suppressed. As a result, further improvement in the operability of the ball screw and reduction in the circulating sound of the rolling elements are further improved as compared with the embodiment in which the cross section of the return path 111 shown in FIG.

As described above, according to the circulating top of this embodiment and the ball screw provided with the same, the return path has a cylindrical shape, is provided with a tongue part and an engaging part, and defines the shape and diameter of the return path. It is possible to further improve the operability of the recirculating top ball screw and to reduce the circulating sound of the rolling elements.
In addition, the circulation top and ball screw which concern on this invention are not limited to the said embodiment, A various deformation | transformation is possible unless it deviates from the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Ball screw 10 Screw shaft 11 Spiral groove 20 Nut 21 Spiral groove 23 Circulation top insertion hole 30 Rolling element (ball)
DESCRIPTION OF SYMBOLS 100 Circulation top 100A 1st division body 100B 2nd division body 101A Joining surface 101B (of 2nd division body) Joining surface 110 Circulation top body 110A Circulation top body 110B of 1st division body 110B 2nd division Body circulation top body 111 Return path 111A Circulation groove of first divided body 120 Engaging portion 120A Engaging portion of first divided body 120B Engaging portion of second divided body 112 Tongue portion 112A Tongue portion of first divided body 113 First alignment unit 114 Second alignment unit

Claims (4)

A screw shaft having a spiral spiral groove on the outer peripheral surface, a nut having a spiral spiral groove on the inner peripheral surface and fitted on the screw shaft, and a track formed by these spiral grooves are disposed. Used in a ball screw including a plurality of rolling elements, mounted on the nut, and provided with a cylindrical return path for returning the rolling elements to a previous track,
A circulation top main body composed of two divided bodies each formed with a return groove for forming the return path and formed with a joining surface orthogonal to the return path, and a ball screw of each of the ball screws from both side surfaces of the divided body. An engaging portion that protrudes along the spiral groove and is provided to limit the movement of the circulating top body;
The circulating top main body is provided with a tongue for guiding the rolling elements into the return path,
The diameter of the return path is more than 1.0 times and less than 1.1 times the rolling element,
A circulating spinning top characterized in that an alignment convex portion and a concave portion are provided on each joint surface of the divided body.   The return path is configured by a straight line for scooping up the rolling element in a direction substantially orthogonal to a scooping angle, and two or more curves and a straight line connecting the curves in the return path. Circulation top of.   The circulating top according to claim 1 or 2, wherein a cross section of the return path has an elliptical shape with a major axis in the radial direction. A screw shaft having a spiral spiral groove on the outer peripheral surface, a nut having a spiral spiral groove on the inner peripheral surface and fitted on the screw shaft, and a track formed by these spiral grooves are disposed. A plurality of rolling elements, and a circulating top having a return groove that is attached to the nut and returns the rolling elements to a previous track,
The said nut is provided with the circulation top insertion hole which mounts the said circulation top, and the circulation top as described in any one of Claims 1-3 is attached to the said circulation top insertion hole as the said circulation top. Ball screw characterized by

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