JP6547429B2 - Ball screw - Google Patents

Description

  The present invention relates to a ball screw having a top as a part forming a ball return path.

  The ball screw has a screw shaft, a nut and a plurality of balls. The screw shaft passes through the nut, and the spiral groove of the screw shaft and the spiral groove of the nut form a ball rolling path. The nut is provided with a ball return path for returning the ball from the end point of the rolling path to the start point. The balls are disposed in a circulation path (circuit) consisting of a rolling path and a ball return path. The ball screw is a device in which the screw shaft and the nut move relative to each other via a ball which circulates in the circulation path and rolls (moves while rotating under load) in the rolling path. The ball return path is formed by attaching a return tube or piece to the nut.

In a top type ball screw having a top as a part for forming a ball return path, the top is mounted in a through hole which passes through a nut in the radial direction. With regard to the mounting method of the top to the through hole, the top is provided with a pair of positioning arms, the top is inserted into the through hole from the inner peripheral surface side of the nut, and each arm is engaged with the spiral groove near the through hole of the nut A method has been proposed (see Patent Documents 1 and 2)
Further, in the methods described in Patent Documents 1 and 2, for the purpose of shortening the axial dimension of the nut, increasing the load capacity, reducing the number of parts, etc., a plurality of grooves for ball return passage are provided in one piece. There is. As a method of fixing the cotter, a method of caulking and a method of using a fixing member having a guide wall which elastically contacts the through hole of the nut are described. Furthermore, in these ball screws, the ball rides on the land (outer peripheral surface) of the screw shaft at the position of the top and then moves to the next spiral groove.

  Patent Document 3 describes a chip (deflector) formed in a tunnel shape in which a ball return path separates a ball from an outer peripheral surface of a screw shaft. In this piece, a ball scooping portion is formed at both ends of the ball return path. Further, it is described that the coma is configured by combining a pair of halves divided along a ball return path.

Patent No. 3845922 Patent No. 3844943 JP 2001-165274 A

A ball screw having a piece in which a plurality of grooves for ball return paths are formed in one piece has room for improvement in that the fixing operation of the piece is simplified.
An object of the present invention is to simplify the work of fixing a piece in a ball screw having a piece in which a plurality of grooves for ball return paths are formed in one piece.

In order to solve the said subject, the ball screw which is the 1st aspect of this invention has following structure (1)-(5).
(1) A screw shaft, a nut, a plurality of balls, a top, and a fixing part for fixing the top to the nut. The screw shaft passes through the nut. A rolling path along which the ball rolls in a loaded state is formed by the helical groove of the screw shaft and the helical groove of the nut. The cotter is a component in which a ball return path is formed to return the ball from the end point of the rolling path to the start point, and is disposed in a through hole penetrating the nut in a direction intersecting the axial direction. The ball is disposed in the rolling path and in the ball return path, and the screw shaft and the nut move relative to each other via the ball rolling in the rolling path.

(2) The piece has a plurality of ball return paths. The ball return path is formed in a tunnel shape by a groove formed in the cotter and a closed portion closing the opening surface of the groove.
(3) The closing portion is provided with a tongue portion for guiding the ball from the end point to the ball return path.
(4) The cotter has a pair of positioning arms extending along the helical groove of the nut. The positioning arm is engaged with a spiral groove near the through hole of the nut.

(5) The nut has an insertion hole for the fixing component in the vicinity of the through hole. The frame is fixed to the nut by fixing a fixing component inserted from the outside into the insertion hole to a fixing portion formed on the positioning arm.
The ball screw of the first aspect of the present invention can have the following configuration (6) in addition to the above configurations (1) to (5). In this case, not only can the fixing operation of the top be simplified, but also the effect of reducing the manufacturing cost of the top can be obtained. The following configuration (6) is not an essential requirement of the present invention.
(6) The frame includes a plurality of divided bodies divided at an end face along the ball return path. The split body has a pair of end pieces having the positioning arm, and an intermediate piece disposed between the pair of end pieces.

  The ball screw of the present invention is a ball screw having a piece in which a plurality of grooves for a ball return path are formed in one piece, and the piece can be fixed easily.

It is a front view showing a ball screw of an embodiment. It is a front view showing a nut which constitutes a ball screw of an embodiment. It is AA sectional drawing of FIG. It is a front view (figure seen from the side arrange | positioned at the outer peripheral surface of a nut) which comprises the ball screw of embodiment. It is a rear view (figure seen from the side arrange | positioned at the internal peripheral surface of a nut) which comprises the ball screw of embodiment. It is sectional drawing which shows the part in which the through-hole of the internal peripheral surface of a nut is formed. It is sectional drawing which shows the internal peripheral surface of the nut in which the piece was attached. It is a figure which divides and shows the top of FIG. 5 to a division body. It is the figure which looked at the division body which is end parts along the division surface of the main-body part shown by AA and BB in FIG. It is a perspective view of a divided body which is an end part. It is BB sectional drawing of FIG. 8 which shows the division body which is intermediate components. It is a figure explaining the fixing method to the nut of coma. It is a figure which is a fixing method to the nut of coma, and is different from FIG. It is a front view (figure seen from the side arrange | positioned at the outer peripheral surface of a nut) of the coma which consists of quarters. It is a rear view (figure seen from the side arrange | positioned at the inner peripheral surface of a nut) which divides and shows the top of FIG. 14 in a division body.

Hereinafter, although the embodiment of this invention is described, this invention is not limited to the embodiment shown below. In the embodiments shown below, technically preferable limitations are made to carry out the present invention, but this limitation is not a requirement of the present invention.
As shown in FIGS. 1 to 3, the ball screw 10 of this embodiment has a screw shaft 1, a nut 2, a plurality of balls 3, a top 4, and a fixing screw (fixed part) 5. The nut 2 comprises a cylindrical portion 2E and a flange portion 2F formed at one end in the axial direction. A spiral groove 11 is formed on the outer peripheral surface of the screw shaft 1, and a spiral groove 21 is formed on the inner peripheral surface 2 b of the nut 2. The screw shaft 1 passes through the nut 2.

  The spiral groove 11 of the screw shaft 1 and the spiral groove 21 of the nut 2 form a rolling path along which the ball 3 rolls. The balls 3 are disposed in three circulation paths including the rolling path and three rows of ball return paths 40A to 40C formed in the top 4. The balls 3 roll under load in the rolling path and circulate in the circulation path. In the ball screw 10, the screw shaft 1 and the nut 2 move relative to each other through the loaded ball 3 in the rolling path.

  A through hole 22 extending from the outer peripheral surface 2a to the inner peripheral surface 2b is formed at one location of the cylindrical portion 2E of the nut 2 so as to penetrate in the direction orthogonal to the axial direction. The through hole 22 has a substantially parallelogram planar shape in which four corners of the parallelogram are rounded. The long side of the parallelogram forming the through hole 22 extends along the axial direction of the nut 2, and the short side is inclined in the axial direction of the nut 2. The top 4 is disposed in the through hole 22 of the nut 2.

In the vicinity of the through hole 22 of the nut 2, two insertion holes 23 of the fixing screw 5 are formed. The insertion holes 23 are formed on a line connecting the center of the through hole 22 and the two short sides of the parallelogram. Each insertion hole 23 includes a small diameter portion 23a in which a shaft portion of the fixing screw 5 is disposed and a counterbore portion 23b in which a head is disposed.
As shown in FIG. 4 and FIG. 5, the top 4 is a positioning arm that extends across the long side from the main side 41 having the same planar shape as the through hole 22 and the parallel sides forming the main body 41. And 42. A female screw hole (fixing portion) 421 is formed at an end of each positioning arm 42.

  The main body portion 41 of the cotter 4 has an outer peripheral surface 411 formed in an arc surface along the outer peripheral surface 2 a of the nut 2 and an inner peripheral surface 412 formed in an arc surface along the inner peripheral surface 2 b of the nut 2. The outer peripheral surface 411 is shown in FIGS. 1 and 4. The inner circumferential surface 412 is shown in FIG. Three rows of grooves 413 a to 413 c are formed on the inner circumferential surface 412 of the main body portion 41. These grooves 413a to 413c are grooves continuous with the end portions of the spiral groove 21 present on both sides of the through hole 22 in a state where the nut 2 is attached to the through hole 22.

As shown in FIG. 6, in the portion where the through hole 22 of the spiral groove 21 of the nut 2 is formed, from the first portion 211 to the fourth portion 214, one end 211a to 214a and the other end 211b to 214b It is divided into
As shown in FIG. 7, by arranging the pieces 4 in the through holes 22, one end of the first groove 413 a is continuous with one end 211 a of the first portion 211, and the other end of the first groove 413 a is the second portion 212. It continues in the other end 212b of. One end of the second groove 413b is continuous with one end 212a of the second portion 212 of the spiral groove, and the other end of the second groove 413b is continuous with the other end 213b of the third portion 213 of the spiral groove. One end of the third groove 413c is continuous with one end 213a of the third portion 213 of the spiral groove, and the other end of the third groove 413c is continuous with the other end 214b of the fourth portion 214 of the spiral groove.

  As shown in FIG. 5, FIG. 7 to FIG. 9, and FIG. 11, the top 4 has the first to third grooves 413a to 413c and the opening surface 403 of each groove 413a to 413c (see FIG. 9 and FIG. 11). Three rows of ball return paths 40A to 40C are formed in a tunnel shape by closed portions 414a to 414c that close the central portion (a part) of the two. A tongue portion 43 for guiding the ball 3 into the ball return path 40 is formed in each of the closed portions 414 a to 414 c in a pair.

Further, as shown in FIG. 7, one positioning arm 42 is fitted to the other end 211b of the first portion 211 of the spiral groove, and the other positioning arm 42 is fitted to one end 214a of the fourth portion 214 of the spiral groove. . The other end 211 b of the first portion 211 of the spiral groove and one end 214 a of the fourth portion 214 of the spiral groove correspond to a spiral groove in the vicinity of the through hole 22 of the nut 2.
As shown in FIGS. 4, 5, and 8, the top 4 is composed of three divided bodies 4A, 4B, and 4C divided at an end face 401 along the ball return paths 40A to 40C. Thus, the main body 41 is divided into three parts 41A to 41C. As shown in FIGS. 8 and 10, the split bodies 4A and 4C are end parts having positioning arms 42. The divided body 4B is an intermediate component disposed between the divided bodies 4A and 4C. As shown in FIG. 8 and FIG. 9, in the end face 401 of the divided members 4A and 4C which are end parts, a protrusion 401a is formed at one end of the grooves 413a and 413c, and a recess 401b is formed at the other end of the grooves 413a and 413c. ing.

  As shown in FIG. 8, a recess 401b is formed at one end of the first groove 413a and a protrusion 401a is formed at the other end of the first groove 413a on one end surface 401 of the divided body 4B which is an intermediate component. There is. On the other end face 401 of the divided body 4B, which is an intermediate part, a protrusion 401a is formed at one end of the third groove 413c, and a recess 401b is formed at the other end of the third groove 413c. Positioning is performed by fitting the convex portion 401 a and the concave portion 401 b between the end members divided bodies 4A and 4C and the intermediate portion divided body 4B.

The split bodies 4A, 4B and 4C can be manufactured by injection molding of synthetic resin. As the synthetic resin, it is preferable to use a resin composition in which a reinforcing material composed of glass fiber, potassium titanate fiber or the like is mixed with PPS (polyphenylene sulfide) or POM (polyacetal).
When assembling the ball screw 10 of this embodiment, first, from the side of the inner peripheral surface 2b of the nut 2, the main body of the cotter 4 in which the divided members 4A to 4C are integrated by fitting the convex portion 401a and the concave portion 401b. The portion 40 is inserted into the through hole 22 and the pair of arms 42 is fitted to the other end 211 b of the first portion 211 of the spiral groove and one end 214 a of the fourth portion 214 of the spiral groove.

  Next, as shown in FIG. 12, two fixing screws 5 are inserted from the outside into the insertion holes 23 from the outside of the nut 2, and the tips thereof are screwed into the female screws of the positioning arms 42. Fix 4 to nut 2. Thereby, three rows of ball return paths 40A to 40C formed in the spiral groove 21 of the nut 2 and the top 4 are connected. Next, the ball 3 and the screw shaft 1 are assembled to the nut 2 using a temporary shaft.

  The ball screw 10 of this embodiment has a piece 4 in which three rows of ball return paths 40A to 40C formed in a tunnel shape are formed, and the piece 4 is fixed to the nut 2 by a fixing screw 5. Therefore, compared with the frame to be fixed by caulking, the fixing operation of the frame is easy. In addition, by fixing the top 4 to the nut 2 with the fixing screw 5, it is possible to avoid that the force component in the gravity direction from the ball is transmitted to the top 4 during ball circulation and the top 4 contacts the screw shaft 1. As a result, malfunction and abnormal heat generation can be prevented, which leads to improvement in the reliability of the ball screw 10.

Furthermore, since the top 4 having the three rows of ball return paths 40A to 40C is configured by the three divisions 4A to 4C, the manufacturing cost of the top is reduced as compared with the integrated top.
In addition, as a fixing method, as shown in FIG. 14, you may use the fixing pin 6 which has the burr part 6a in the front-end | tip as a fixing component. In this case, the arm 42 of the top 4 is provided with a through hole 422 including a small diameter hole 422a for disposing the shaft portion of the fixing pin 6 and a large diameter portion 422b for engaging the burr portion 6a.

  Further, the divided body 4B, which is an intermediate component, can be further divided into two divided bodies 4D and 4E. The top 400 shown in FIGS. 14 and 15 is composed of four divided bodies 4A, 4C, 4D, 4E divided at an end surface 401 along the ball return paths 40A to 40C. In this case, the main body 41 of the top 400 is divided into four parts 41A, 41C, 41D, and 41E.

In the cotter 400 shown in FIGS. 14 and 15, the divided members 4A and 4C which are end parts are the same as described above. That is, the figure which looked at the division bodies 4A and 4C which are end components along the division surface of the main-body part shown by AA and BB in FIG. 14 is the same as FIG.
A recess 401b is formed at one end of the first groove 413a and a protrusion 401a is formed at the other end of the first groove 413a on one end surface 401 of the divided body 4D which is an intermediate component. On the other end face 401 of the divided body 4D, which is an intermediate part, a protrusion 401a is formed at one end of the second groove 413b, and a recess 401b is formed at the other end of the second groove 413b.

A recess 401b is formed at one end of the second groove 413b and a protrusion 401a is formed at the other end of the second groove 413b on one end face 401 of the divided body 4E which is an intermediate component. On the other end surface 401 of the divided body 4E which is an intermediate part, a convex portion 401a is formed at one end of the third groove 413c, and a concave portion 401b is formed at the other end of the third groove 413c.
Between the divided body 4A which is an end part and the divided body 4D which is an intermediate part, between the divided body 4C which is an end part and the divided body 4E which is an intermediate part, the divided body 4D which is an intermediate part and the divided body 4E The positioning is performed by fitting the convex portion 401 a and the concave portion 401 b between them.

  The divided bodies 4D and 4E, which are intermediate parts, are the same parts, and their shape is simple as compared with the divided body 4B. Therefore, the top 400 can reduce the manufacturing cost more than the top 4.

DESCRIPTION OF SYMBOLS 10 ball screw 1 screw shaft 11 helical groove of screw shaft 2 nut 2E cylindrical portion of 2F nut flange portion of nut 2a outer circumferential surface of nut 2b inner circumferential surface of nut 21 helical groove of nut 211 first portion (through hole of helical groove Part formed)
212 second part (the part where the through hole of the spiral groove is formed)
213 Third part (the part where the through hole of the spiral groove is formed)
214 Fourth part (the part where the through hole of the spiral groove is formed)
22 Nut through-hole 23 Fixing screw through-hole 3 Ball 4 top 400 top 4A end part (split body)
4B Intermediate parts (split body)
4C end part (split body)
4D intermediate parts (split bodies)
4E Intermediate parts (split bodies)
40A to 40C Ball Return Path 41 Body Part 401 End Surface Along the Ball Return Path of Divided Body 401a Convex Part 401b Concave Part 411 Outer Peripheral Surface of Main Body Part 412 Inner Peripheral Surface of Main Body Part 413a to 413c Groove 414a to 414c Closed Part 403 Opening of Groove Surface 42 Positioning arm 421 Female screw hole (fixed part)
422 Through hole (through hole for fixed part)
43 Tongue 5 Fixing screw (Fixing part)
6 Fixing pin (fixing part)
6a Kaeri Department

Claims (2)

A screw shaft, a nut, a plurality of balls, a piece, and a fixing part for fixing the piece to the nut;
The screw shaft passes through the nut,
The spiral groove of the screw shaft and the spiral groove of the nut form a rolling path along which the ball rolls in a loaded state,
The cotter is a component in which a ball return path is formed to return the ball from the end point of the rolling path to the start point, and is disposed in a through hole penetrating the nut in a direction intersecting the axial direction.
The ball is disposed in the rolling path and the ball return path, and the screw shaft and the nut move relative to each other via the ball rolling in the rolling path.
The piece has a plurality of ball return paths,
The ball return path is formed in a tunnel shape by a groove formed in the cotter and a closing portion closing the opening surface of the groove.
The closed portion is formed with a tongue portion for guiding the ball from the end point to the ball return path,
The cotter has a pair of positioning arms extending along a helical groove of the nut,
The positioning arm is engaged with a spiral groove near the through hole of the nut;
The nut has an insertion hole for the fixing component in the vicinity of the through hole,
The ball screw is fixed to the nut by fixing a fixed part, which is inserted from the outside into the insertion hole, to a fixed portion formed on the positioning arm. The coma comprises a plurality of divided bodies divided at an end face along the ball return path,
The ball screw according to claim 1, wherein the divided body includes a pair of end parts having the positioning arm, and an intermediate part disposed between the pair of end parts.

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