JP2024043041A - ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw capable of actualizing less components, lower costs and higher reliability by devising a shape of a cutout part where a circulation piece is arranged for fixing the circulation piece to a nut without using a set screw.

SOLUTION: A cutout part 58 of a nut 54 includes a key groove 71 formed in a range from an outer peripheral face to an axial center, and having a longitudinal direction along the axial direction of the nut, and a long hole 72 formed in a range from an outer diameter side opening of the key groove 71 along a ball scooping direction α of a circulation piece 10 arranged in the cutout part 58, and having a bottom wall face 72a on which the circulation piece 10 abuts, the key groove 71 including an engagement recessed part 70 formed by a bottom face 71b and a peripheral face 71a which do not overlap with the long hole 72, the circulation piece 10 having an engagement protruded part 26 for engaging with the engagement recessed part 70.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a ball screw equipped with a circulation piece built into a nut.

A conventional ball screw is shown in FIG. 7 (see, for example, Patent Document 1). This ball screw 50 comprises a screw shaft 52 that has a helical screw groove 51 on its outer circumferential surface and extends in the axial direction, and a nut 54 that has a helical screw groove 53 on its inner circumferential surface that corresponds to the screw groove 51 of the screw shaft 52. The screw groove 51 of the screw shaft 52 and the screw groove 53 of the nut 54 face each other to form a load track 55 between them, and a large number of balls 56 are loaded in the load track 55 so that they can roll as rolling elements.

Further, a ball return passage 57 is formed inside the nut 54 and passes through the nut 54 in the axial direction, and the ends of the ball return passage 57 are opened at two locations in the axially intermediate portion of the nut 54 and at both ends thereof. Four recesses (notches) 58 are formed, respectively. A circulation piece 60 for communicating the ball return passage 57 and the load track 55 is fitted and fixed in each of the four recesses 58 . A ball circulation passage 61 is formed inside the circulation piece 60 and is curved so as to communicate between the ball return passage 57 and the load track 55. Therefore, in the embodiment shown in FIG. 7, two circulation paths for the balls 56 are configured in the nut 54.

As shown in FIG. 8, the circulation piece 60 includes a first circulation piece 62 which is divided into two parts on the center line of the rolling locus of the ball 56, and is provided with ball circulation grooves 64 and 65 each having a substantially semicircular cross section. A ball circulation passage 61 is formed by abutting the second circulation piece 63 and the second circulation piece 63. The first circulation piece 62 is provided with a tongue portion 66 at the tip of the ball circulation groove 64 for scooping up the balls 56 from the load track 55.

The load track 55, the ball circulation path 61 of one circulation piece 60, the ball return path 57, the ball circulation path 61 of the other circulation piece 60, and the load track 55 form an endless ball circulation path. In the ball screw 50, the rotation of the screw shaft 52 (or the nut 54) causes the nut 54 (or the screw shaft 52) to move in the axial direction through the rolling of the balls 56.

Furthermore, in Patent Document 2, a positioning protrusion provided on a deflector (circulation piece) is fitted into a positioning fitting part of a mounting hole of a nut, so that a positioning protrusion provided on a deflector (circulation piece) is fitted in a height direction between a communication hole of the nut and a connecting path of the deflector. A ball screw device is also described that performs angular positioning.

Patent No. 5170330 JP2008-38920A

In the ball screw described in Patent Document 1, a separate part for fixing the circulation piece is prepared, and the circulation piece is fixed to the nut using a set screw or the like. Therefore, the nut requires processing such as a tapped hole, and further parts such as a holding part for the circulation piece and a set screw are required. Therefore, the number of parts increases, manufacturing costs increase, and there is a possibility that set screws and the like may come loose, making it difficult to ensure reliability over a long period of time. Further, in the ball screw device described in Patent Document 2, it is necessary to separately process a positioning fitting part for fitting the deflector into a mounting hole, which causes a problem that the manufacturing cost increases.

The present invention has been made in view of the above-mentioned problems, and its purpose is to attach the circulation piece to a nut without using a set screw or the like, and by devising the shape of the notch in which the circulation piece is placed. The object of the present invention is to provide a ball screw which can reduce the number of parts by fixing the ball screw to the ball screw, is low in cost, and has high reliability.

The above object of the present invention is achieved by the following configuration.
[1] A screw shaft with a spiral thread groove formed on the outer peripheral surface, a nut with a spiral thread groove formed on the inner peripheral surface and a notch provided on the outer peripheral surface, and a screw of the screw shaft. A plurality of balls rolling on a load track formed by a groove and a thread groove of the nut, and a ball circulation passage disposed in the notch of the nut and circulating the balls rolling on the load track. A ball screw comprising: a circulating piece that forms a circular piece;
The notch portion is formed from the outer circumferential surface toward the axial center, and has a key groove whose longitudinal direction is along the axial direction of the nut, and a ball scooping direction of the circulation piece disposed in the notch portion. , an elongated hole formed from an opening on the outer diameter side of the keyway and having a bottom wall surface with which the circulation piece comes into contact;
The keyway includes an engagement recess formed by a bottom surface and a peripheral surface that do not overlap the elongated hole,
The circulation piece has an engagement protrusion that engages with the engagement recess.
ball screw.

According to the ball screw of the present invention, the number of parts can be reduced by fixing the circulation piece to the nut without using a set screw or the like, and by devising the shape of the notch in which the circulation piece is placed. , low cost and high reliability.

1(a) is a plan view of a nut having a notch, and FIG. 1(b) is a sectional view taken along line AA in FIG. 1(a). The circulation piece in which the first circulation part and the second circulation part are assembled is shown; (a) is a front view, (b) is a left side view, (c) is a right side view, and (d) is a top view. be. The first circulating component shown in FIG. 2 is shown, in which (a) is a front view, (b) is a left side view, (c) is a right side view, (d) is a top view, and (e) is a bottom view. . 3A, 3B, 3C, 3D are views showing the second circulatory component shown in FIG. 2, in which FIG. 3A is a rear view, FIG. 3B is a right side view, FIG. 5(a) is a plan view, and FIG. 5(b) is a side view of FIG. 5(a). FIG. 6A and 6B show a nut in which a long hole is formed as a second machining step of the cutout portion, in which (a) is a plan view and (b) is a side view of FIG. 6A . FIG. 3 is a cross-sectional view of a conventional ball screw. FIG. 8 is an exploded plan view of the circulating piece shown in FIG. 7;

Hereinafter, a ball screw according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 4. Regarding the ball screw of this embodiment, parts that overlap with the conventional ball screw 50 already described in FIGS. 7 and 8 are designated by the same reference numerals in each figure, and the description thereof will be omitted.

That is, as shown in FIG. 1, the nut 54 to which the circulating piece 10 of this embodiment is assembled has a helical screw groove 53 formed on its inner surface, and a pair of notches 58 that are cut out from the radially outer side and opposed in the axial direction are formed on its outer surface.
In addition, while the conventional ball screw 50 has two circulation paths for the balls 56 configured within the nut 54, the ball screw of the present embodiment has one circulation path for the balls 56 configured within the nut 54.

In addition, in the following description, regarding the nut 54 and the circulation piece 10, the X direction, Y direction, and Z direction are defined based on the direction of the nut to be assembled. Specifically, as shown in FIGS. 1 to 4, the X direction is a direction along the rotation axis O of the nut 54, and the Y direction is a radial direction toward the rotation axis O of the nut 54, and any circulation This is the processing direction of the keyway 71 that forms part of the notch 58 to which the piece 10 is attached, and the Z direction is a direction perpendicular to both the X direction and the Y direction. The α direction is the direction in which the balls 56 of one circulation piece are scooped up, and the β direction is the direction perpendicular to the direction in which the balls 56 are scooped up.

The notch 58 is formed from the outer circumferential surface toward the shaft center to approximately the middle of the depth of the nut 54, and its longitudinal direction extends along the keyway 71 along the axial direction of the nut 54 and the direction in which the ball 56 is scooped up. The key groove 71 includes a pair of elongated holes 72 formed from openings on the outer diameter side at both ends of the key groove 71.

That is, the cutout portion 58 is formed by keyway machining to form a keyway 71, shown in FIG. 5, and end milling to form a pair of elongated holes 72, shown in FIG. The pair of elongated holes 72 are machined so as to be inclined in opposite directions at the same angle with respect to the Y direction in which the keyway 71 is formed. In addition, in the end milling process, the slotted hole 72 is not opened in the inner peripheral surface of the nut 54 in the same direction as the slotted hole 72 (alpha direction in FIG. 1), to the side in the X direction where the direction change portion 42 (described later) of the slotted hole 72 faces. A lateral groove 73 is formed.

Then, by keyway machining and end milling, the corners of the bottom surface 71b and peripheral surface 71a of the keyway 71 that do not overlap with the elongated hole 72 engage with the engagement protrusion 26 of the first circulating component 20, which will be described later. A matching recess 70 is formed.
The pair of elongated holes 72 are partially open to the inner circumferential surface of the nut 54, and have a bottom wall surface 72a on the inner diameter side with which the circulation piece 10 abuts.

As shown in FIG. 2, the circulation piece 10 is formed by abutting two parts, a first circulation part 20 and a second circulation part 30, against each other. The circulation piece 10 has a curved ball circulation passage 40 inside thereof. The first circulating component 20 and the second circulating component 30 are divided into two along a plane passing through the centerline of the ball circulating passage 40. Then, the abutting surface 21a, which is the first joint surface of the first circulating component 20, and the abutting surface 31a, which is the second joining surface of the second circulating component 30, are butted to form the circulation piece 10, It is arranged within the notch portion 58 .

The ball circulation passage 40 includes a linear scooping part 41 that scoops up the ball 56 from the load track 55 by the tongue part 25 or returns the ball 56 to the load track 55, and a curved part to change the moving direction of the ball 56. It is provided with a direction changing part 42 and is formed in a substantially L-shape in the Xα plane. In addition, the center line C of the ball circulation passage 40 is different from that in the scooping part 41, where the position of the circulation piece 10 in the thickness direction (β direction) perpendicular to the abutting surfaces 21a and 31a does not change, whereas in the direction changing part 42 communicates with the ball return passage 57, so its position in the β direction curves toward the first circulating component 20 as it moves away from the scooping part 41.

Such a ball circulation passage 40 includes a first ball circulation groove 24 formed on the abutting surface 21a of the first circulating component 20 and a second ball circulating groove 24 formed on the abutting surface 31a of the second circulating component 30. It is constituted by a circulation groove 34.

As shown in FIG. 3, the first circulating component 20 includes a main body 21 having an outer shape corresponding to the shape of the notch 58 of the nut 54, and a main body 21 that protrudes from the main body 21 in the α direction and rolls on a load raceway 55. and a tongue part 25 that scoops up the ball 56. The main body portion 21 is provided with an engagement convex portion 26 that is approximately triangular in side view and that engages with the engagement recess 70 of the nut 54 and protrudes in a direction opposite to the abutting surface 21a.

In the first circulating component 20 , the engagement convex portion 26 is inserted into the notch 58 along the circumferential surface 71 a of the keyway 71 and is disposed in contact with the bottom surface 71 b of the keyway 71 .

Further, on the abutting surface 21a of the main body portion 21, an engaging portion 27 having a substantially triangular cross section and having a substantially rectangular shape when viewed from the front is provided so as to protrude from the abutting surface 21a. One slope 27a of the engaging portion 27 rises substantially perpendicularly from the abutting surface 21a, and the other slope 27b slopes so as to gradually protrude from the abutting surface 21a from the direction change groove 23 toward the scooping groove 22. There is.

The first ball circulation groove 24 includes a substantially flat scooping groove 22 formed by one surface of the tongue portion 25 and a direction changing groove 23 formed in a continuous curve from the scooping groove 22. . The scooping groove 22 and the direction changing groove 23 are formed to have a substantially semicircular cross section.

The scooping groove 22 is formed linearly along the lead angle direction and partially constitutes the scooping section 41, while the direction change groove 23 is curved in the Xα plane and bent in the β direction in the βα plane to partially constitute the direction change section 42.

The second circulating component 30 includes a main body portion 31 having an outer shape corresponding to the shape of the notch portion 58 of the nut 54, as shown in FIG. Further, the second circulating component 30 includes an abutting surface 31a that is a second bonding surface for bonding to the first bonding surface (butting surface 21a) of the first circulating component 20. A second ball circulation groove 34, which is substantially L-shaped in the Xα plane and constitutes the other part of the ball circulation passage 40, is formed in the abutting surface 31a.

The second ball circulation groove 34 includes a straight groove 32 that has a substantially semicircular cross section and extends in the α direction, and a direction change groove 33 that has a roughly semicircular cross section and is formed by continuing from the straight groove 32 and curving in the X direction. Equipped with.

The straight groove 32 is arranged opposite to the scooping groove 22 of the first circulating component 20 and partially constitutes the scooping part 41, and the direction changing groove 33 is arranged opposite to the scooping groove 22 of the first circulating component 20. They are arranged to face each other and partially constitute the direction changing section 42.

Further, a concave engaged portion 37 is formed on the abutting surface 31a of the second circulating component 30, which is approximately rectangular in front view and has a slightly larger area than the engaging portion 27 of the first circulating component 20. has been done. The engaged portion 37 is a recessed portion having a substantially triangular cross section formed to correspond to the engaging portion 27 of the first circulating component 20, and one slope 37a is formed substantially perpendicular to the abutting surface 31a. The other slope 37b is formed to be inclined so that the depth gradually increases from the direction change groove 33 toward the straight groove 32.

The portion where the engaged portion 37 is formed is triangular with a pointed tip, making the thickness near the engaged portion 37 thinner and allowing it to be elastically deformable.

Thereby, the engaged portion 37 engages with the engaging portion 27 when the abutting surface 31a of the second circulating component 30 abuts against the abutting surface 21a of the first circulating component 20. (See Figure 2).

Next, a procedure for assembling the circulation piece 10 into the notch 58 of the nut 54 will be explained.
In the circulation piece 10 configured in this way, the engaging protrusion 26 of the first circulation component 20 is inserted into the notch 58 along the circumferential surface 71a of the keyway 71, and the bottom surface of the keyway 71 is inserted into the notch 58. 71b and assemble it. Thereby, the circulation piece 10 is positioned with the engagement protrusion 26 engaging with the engagement recess 70 of the notch 58.

Next, the second circulating component 30 is inserted from the end 31b on the straight groove 32 side along the long hole 72 of the notch 58 so as to cover the first circulating component 20. The abutting surface 21a of the second circulating component 30 and the abutting surface 31a of the second circulating component 30 are abutted, and the end 31b on the straight groove 32 side is brought into contact with the bottom wall surface 72a of the elongated hole 72.

At this time, the engaging portion 27 of the first circulating component 20 interferes with the abutting surface 31a of the second circulating component 30, but the thickness near the engaged portion 37 of the second circulating component 30 is thin. The portion is pushed in while being elastically deformed, and the engaging portion 27 of the first circulating component 20 and the engaged portion 37 of the second circulating component 30 are engaged and assembled.
Note that the second circulating component 30 is preferably made of resin so that it can be easily elastically deformed. Furthermore, although the first circulating component 20 is also made of resin, it may be made of other materials.

Similarly, by placing the other first circulating component 20 and second circulating component 30 in the other notch 58 according to the procedure explained above, the load track 55 and one circulating piece 10 An endless circulation path is formed by the ball circulation path 40 of , the ball circulation path 40 of the other circulation piece 10 , and the load track 55 . At this time, the pair of circulation pieces 10 are assembled so that the directions of attachment to the nuts 54 are 180 degrees different from each other, and the direction changing parts 42 are arranged so as to be directly connected to each other.

When the nut 54 (or the screw shaft 52) rotates, the balls 56 are scooped up from the load track 55 by the scooping section 41, changed direction at the direction change section 42 of the circulating piece 10, and then returned to a different position of the load track 55 from the other circulating piece 10 and circulated. As a result, the screw shaft 52 (or the nut 54) moves in the axial direction via the rolling of the balls 56.

By assembling in this way, the first circulating component 20 is positioned with the engaging convex portion 26 engaging with the engaging recess 70 of the notch 58, and the second circulating component 30 is positioned with the engaging convex portion 26 engaged with the engaging recess 70 of the notch 58. The side end portion 31b contacts the bottom wall surface 72a of the elongated hole 72, and the engaged portion 37 of the second circulating component 30 engages with the engaging portion 27 of the first circulating component 20. Thereby, the circulation piece 10 is assembled to the notch 58 in a manner that cannot be disassembled.

Therefore, the circulation piece 10 can be fixed in the notch 58 without using parts or setscrews that prevent the circulation piece 10 from coming out of the notch 58, which are necessary in conventional ball screws, and the number of parts can be reduced. can reduce production costs. In addition, there is no fear that set screws or the like may come loose, improving reliability and allowing stable performance to be maintained over a long period of time.
In addition, since the engagement recess 70 of the notch 58 is constituted by a keyway 71 formed for arranging the part of the circulation piece 10 that constitutes the direction change part 42, there is no need for separate machining. Costs can be reduced.

Note that the present invention is not limited to the embodiments described above, and can be modified, improved, etc. as appropriate. For example, although the circulating piece 10 has been described as a combination of the first circulating component 20 and the second circulating component 30, the first circulating component 20 and the second circulating component 30 may also be formed integrally. can.

Furthermore, although the pair of circulation pieces 10 have been described as being assembled so that the direction changing parts 42 are directly connected to each other in the axial direction, they are connected via a ball return passage 57 formed to penetrate inside the nut 54 in the axial direction. You can also. In this case, the number of balls 56 incorporated in the endless circulation passage can be increased, and the allowable load capacity of the ball screw can be increased. Further, in the above embodiment, the engaging portion 27 and the engaged portion 37 are described as a convex portion and a concave portion each having a triangular cross section. It may be formed as

Further, the ball screw of the present invention can be used, for example, in an XY stage used for positioning of a device that performs high-precision processing and measurement, semiconductor manufacturing, and the like. Further, it can be used, for example, in machine tools (machining centers, lathes, grinding machines, etc.), measuring machines (three-dimensional measuring instruments), semiconductor manufacturing equipment (tables for exposure equipment, inspection probes, etc.), and the like.

As described above, the present specification discloses the following:
(1) A ball screw comprising: a threaded shaft having a helical thread groove formed on its outer peripheral surface; a nut having a helical thread groove formed on its inner peripheral surface and a notch provided on its outer peripheral surface; a plurality of balls rolling on a load track formed by the thread groove of the threaded shaft and the thread groove of the nut; and a circulation piece disposed in the notch of the nut and forming a ball circulation passage for circulating the balls rolling on the load track,
the notch portion is formed from the outer peripheral surface toward the axial center, and includes a key groove whose longitudinal direction is along the axial direction of the nut, and a long hole formed from an outer diameter side opening of the key groove along a scooping direction of the balls of the circulating piece arranged in the notch portion, and having a bottom wall surface with which the circulating piece abuts;
the key groove has an engagement recess formed by a bottom surface and a peripheral surface that do not overlap the long hole,
The circulating piece has an engaging protrusion that engages with the engaging recess.
Ball screw.
With this configuration, by fixing the circulation piece to the nut without using locking screws, etc., and by devising the shape of the cutout portion in which the circulation piece is positioned, the number of parts can be reduced and manufacturing costs can be reduced, and there is no risk of locking screws, etc. loosening, so high reliability can be maintained over a long period of time.

(2) The ball screw according to (1), wherein the circulation piece is made of elastically deformable resin.
According to this configuration, the ease of assembling the nut and the circulation piece is improved by elastically deforming and assembling the circulation piece.

(3) A pair of circulation pieces are arranged in the notch of the nut,
The ball screw according to (1) or (2), wherein the notch has a pair of elongated holes formed at both ends of the keyway.
According to this configuration, the parts forming the direction change paths of the pair of circulation pieces are arranged in the key grooves, and the respective direction change paths are directly connected, so that the manufacturing cost of the nut can be reduced.

(4) the circulation piece is a first circulation component having a tongue portion that scoops up the balls rolling on the load track; and a first ball circulation groove forming a part of the ball circulation passage; a second circulation component having a second ball circulation groove constituting the other part of the ball circulation passage;
The first circulation component includes the engagement convex portion that engages with the engagement recess of the notch, and an engagement portion provided on a first joint surface in which the first ball circulation groove is formed. and,
The second circulating component is disposed within the notch in contact with the bottom wall surface of the elongated hole, and is provided on a second joint surface in which the second ball circulating groove is formed. The ball screw according to any one of (1) to (3), which has an engaged portion that engages with the engaging portion.
According to this configuration, the engaging convex portion of the first circulating component is engaged with the engaging recess of the nut, and the engaged portion of the second circulating component is engaged with the engaging portion of the first circulating component. This eliminates the need for a member to prevent the circulation piece from falling off from the notch, reducing manufacturing costs and maintaining high reliability over a long period of time.

10 Circulation piece 20 First circulation component 21a Butt surface (first joint surface)
24 First ball circulation groove 25 Tongue portion 26 Engagement convex portion 27 Engagement portion 30 Second circulation component 31a Abutment surface (second joint surface)
34 Second ball circulation groove 37 Engaged part 40 Ball circulation passage 50 Ball screws 51, 53 Thread groove 52 Thread shaft 54 Nut 55 Load raceway 56 Ball 58 Notch 70 Engagement recess 71 Keyway 71a Circumferential surface 71b Bottom surface 72 Long hole 72a Bottom wall surface O Rotating shaft (axis center)
α Ball scooping direction

Claims (4)

A ball screw comprising: a threaded shaft having a helical thread groove formed on its outer circumferential surface; a nut having a helical thread groove formed on its inner circumferential surface and a notch provided on its outer circumferential surface; a plurality of balls that roll on a load-bearing track formed by the thread groove of the threaded shaft and the thread groove of the nut; and a circulation piece that is disposed in the notch of the nut and forms a ball circulation passage for circulating the balls rolling on the load-bearing track,
the notch portion is formed from the outer peripheral surface toward the axial center, and includes a key groove whose longitudinal direction is along the axial direction of the nut, and a long hole formed from an outer diameter side opening of the key groove along a scooping direction of the balls of the circulating piece arranged in the notch portion, and having a bottom wall surface with which the circulating piece abuts;
the key groove has an engagement recess formed by a bottom surface and a peripheral surface that do not overlap the long hole,
The circulating piece has an engaging protrusion that engages with the engaging recess.
Ball screw. The ball screw according to claim 1, wherein the circulation piece is made of elastically deformable resin. A pair of circulation pieces are arranged within the notch of the nut,
The ball screw according to claim 1, wherein the notch has a pair of elongated holes formed at both ends of the keyway. The circulation piece includes a first circulation part having a tongue portion that scoops up the balls rolling on the load track, a first ball circulation groove forming a part of the ball circulation passage, and a second circulation component having a second ball circulation groove constituting the other part of the passage;
The first circulation component includes the engagement convex portion that engages with the engagement recess of the notch, and an engagement portion provided on a first joint surface in which the first ball circulation groove is formed. and,
The second circulating component is disposed within the notch in contact with the bottom wall surface of the elongated hole, and is provided on a second joint surface in which the second ball circulating groove is formed. The ball screw according to claim 1, further comprising an engaged portion that engages with the engaging portion.

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