JP3150527U - Rolling element screw device - Google Patents

Abstract

A rolling element screw device capable of preventing a split return pipe from opening at a joint surface is provided. A return pipe 10 of a rolling element screw device connects one end and the other end of a load ball rolling groove of a nut so as to circulate the ball. The return pipe 10 is formed by adhesively joining the two divided pieces 21 and 22. Each divided piece 21, 22 has joint surfaces 21 a, 22 a formed in a concavo-convex shape in which the convex portion 21 b and the concave portion 21 c are repeated. And the side surface 27 of the convex part 21b is located in the plane P2 orthogonal to the centerline of the return pipe 10. [Selection] Figure 6

Description

  The present invention relates to a rolling element screw device in which a rolling element is interposed between a screw shaft and a nut so as to be capable of rolling motion, and the rolling element is circulated by a return pipe.

  Ball screws with a ball interposed between the screw shaft and nut can reduce the friction generated between the screw shaft and nut, so positioning of machine tools and semiconductor / liquid crystal manufacturing equipment as machine elements It is incorporated in various machines such as a mechanism, a feed mechanism, or a steering gear of an automobile.

  When the screw shaft is rotated relative to the nut, the ball rolls on the loaded ball rolling path between the ball rolling groove of the screw shaft and the loaded ball rolling groove of the nut. The ball rolled to one end of the load ball rolling groove of the nut is picked up by a return pipe provided in the nut and returned to the other end of the load ball rolling groove.

  The return pipe for circulating the balls is generally manufactured by bending a metal pipe with a press. In recent years, from the viewpoint of ease of processing, as shown in FIG. 9, a pair of divided pieces divided along the axial direction are joined, and after fitting into the nut holes in this state, the nut is pressed by a tube presser. A return pipe is proposed that is fixed to (see, for example, Patent Document 1 and Claim 1). In this return pipe, in order to prevent the joining surfaces 2 of the split pieces from being displaced from each other, an uneven portion 3 that is fitted to the joining surface 2 is provided.

JP 2003-343683 A

  When a ball screw is used in an overloaded condition (for example, a ball screw used in an injection molding machine is overloaded when filled with resin), the circulation of the ball in the return pipe is hindered. There is. Then, the meandering ball pushed the inner wall of the return pipe 1, and the return pipe was opened at the joint surface by the pressure of the ball 4.

  To explain the opening phenomenon in detail, when an overload is applied to the ball screw, the amount of elastic deformation of the ball on the loaded ball rolling path becomes larger than a specified value, and the loaded ball rolling path is also narrowed. In this case, as shown in FIG. 10, it becomes difficult for the ball 4 to enter the loaded ball rolling path 5. Since the balls 4 enter one after another from the loaded ball rolling path 6 on the opposite side of the return pipe 1, the clogged balls in the return pipe 1 meander and push the inner wall of the return pipe 1. When the force of pushing the return pipe 1 of the ball 4 is stronger than the force of joining the return pipe 1 divided into two, the joining surface of the return pipe 1 becomes the escape path of the ball 4 and the return pipe 1 opens at the joining surface. .

  The return pipe described in Patent Document 1 cannot prevent the joint surface from opening when the ball screw is overloaded even if the joint surface can be prevented from shifting.

  Then, an object of this invention is to provide the rolling element screw apparatus which can prevent that a return pipe opens at a joining surface.

  The present invention will be described below. In addition, in order to make an understanding of this invention easy, the reference number of an accompanying drawing is attached in brackets, However, This invention is not limited to the form of illustration.

  In order to solve the above-mentioned problem, the invention described in claim 1 is a screw shaft in which a spiral rolling element rolling groove is formed on the outer peripheral surface, and a spiral facing the rolling element rolling groove on the inner peripheral surface. And a pair of legs bent with respect to the center and the center, and one end and the other end of the load rolling element rolling groove of the nut It comprises a return pipe to be connected, a loaded rolling element rolling path between the rolling element rolling groove of the screw shaft and the loaded rolling element rolling groove of the nut, and an unloaded rolling element return passage in the return pipe. A rolling element screw device comprising: a plurality of rolling elements arranged in a rolling element circulation path that circulates as the screw shaft rotates relative to the nut; and the return pipe is divided into two parts Each piece is divided into a convex part and a concave part. Repeat has a bonding surface that is formed in an uneven shape, the side surface of the convex portion is a rolling body screw device located in a plane perpendicular to the center line of the return pipe.

  The invention according to claim 2 is the rolling element screw device according to claim 1, wherein the top surface of the convex portion and the bottom surface of the concave portion are located in a plane parallel to the center line of the return pipe, and The top surface of the convex part and the bottom surface of the concave part are separated from a plane including the center line of the central part and the center line of the leg part.

  According to the first aspect of the present invention, since the side surface of the convex portion of the joint surface is located in a plane orthogonal to the center line of the return pipe, the force to open the return pipe at the joint surface is It becomes a shearing force on the side. Since a force F for opening the return pipe is received as a shearing force on the side surface of the convex portion bonded and bonded, it is possible to withstand a large force for opening the return pipe.

  According to the second aspect of the present invention, since the rolling element is separated from the portion (on the plane including the center line of the center part and the center line of the leg part) that is easy to push the inner wall of the return pipe, it opens to the return pipe. Power is hard to work.

The perspective view (including a partial sectional view) which shows the ball screw in one embodiment of the present invention Sectional view showing the ball screw (FIG. (A) shows a sectional view orthogonal to the axis of the screw shaft, and FIG. (B) shows a sectional view along the screw shaft) Return pipe perspective view Diagram showing the circulation track of the ball (Figure (A) shows the circulation track as seen from the axial direction of the screw shaft, Figure (B) shows a plan view of the circulation track, and Figure (C) shows from the side of the return pipe. (Circuit orbit is shown, Figure (D) shows the orbit seen from the side of the screw shaft) The perspective view which shows the divided piece divided into two The figure which shows the division | segmentation piece divided into two (a figure (A) shows a side view, a figure (B) shows a top view, and a figure (C) shows a front view) Top view of return pipe Schematic diagram showing the elasticity of the convex side Figure showing a conventional return pipe (Figure (B) shows a front view, Figures (A) and (C) show left and right side views of (B)) Sectional view showing circulation of balls in a conventional return pipe

  FIG. 1 shows a ball screw as a rolling element screw device according to an embodiment of the present invention. This ball screw includes a screw shaft 7 having a spiral ball rolling groove 7a formed on the outer peripheral surface, and a nut 8 having a load ball rolling groove 8a opposed to the ball rolling groove 7a formed on the inner peripheral surface. A plurality of balls 9 are interposed between them so as to allow rolling motion. Between the plurality of balls 9, a spacer 23 for preventing contact between the balls 9 is interposed as necessary.

  A spiral ball rolling groove 7 a having a predetermined lead is formed on the outer periphery of the screw shaft 7. The cross-sectional shape of the ball rolling groove 7a is formed as a circular arc groove composed of a single arc or a Gothic arch groove formed by combining two arcs. Since the ball 9 rolls on the ball rolling groove 7a of the screw shaft 7, the surface of the ball rolling groove 7a is hardened. Various types of screws such as a single thread, a double thread, and a triple thread can be used.

  On the inner peripheral surface of the nut 8 through which the screw shaft 7 passes, a spiral load ball rolling groove 8a facing the ball rolling groove 7a of the screw shaft 7 is formed. The cross section of the load ball rolling groove 8a is also formed as a circular arc groove formed of a single arc or a Gothic arch groove combining two arcs. Since the ball 9 rolls on the loaded ball rolling groove 8a, the surface of the loaded ball rolling groove 8a is also hardened. A flat surface portion 8b is formed on the side surface of the nut 8, and a fitting hole 8c into which the leg portion 12 of the return pipe 10 is inserted is formed in the flat surface portion 8b. The fitting hole 8 c penetrates to the inner peripheral surface of the nut 8 and is connected to the load ball rolling groove 8 a on the inner peripheral surface of the nut 8.

  The ball 9 rolled to one end of the load ball rolling groove 8a of the nut 8 is returned to the original position of the load ball rolling groove 8a several turns before by the return pipe 10. The inner diameter of the return pipe 10 is slightly larger than the diameter of the ball 9. In the return pipe 10, the front ball 9 moves while being pushed by the subsequent ball 9.

  The return pipe 10 has a central portion 11 attached to the flat portion 8b of the nut 8 and a pair of leg portions 12 bent with respect to the central portion 11, and is formed in a gate shape as a whole. As shown in FIG. 3, an extension portion 11a is integrally formed in the central portion 11, and an attachment hole 11b through which a screw as a coupling means passes is formed in the extension portion 11a. The return pipe 10 is attached to the nut 8 by inserting the pair of leg portions 12 of the return pipe 10 into the fitting holes 8 c on the side surface of the nut 8 and fixing the central portion 11 to the side surface of the nut 8 with a coupling means. At the tip of the leg portion 12 of the return pipe 10, there is provided a scooping portion 12d that scoops up the ball rolling on the load ball rolling path, guides it into the return pipe, and returns the ball moving in the return pipe to the load ball rolling path. .

  As shown in FIG. 2A, the pair of leg portions 12 of the return pipe 10 are disposed in the tangential direction 14 of the center line of the load ball rolling path 13 when viewed from the axial direction of the screw shaft. Then, as shown in FIG. 2B, when viewed from the side surface direction of the screw shaft 7, the angle α is inclined to coincide with the lead angle of the load ball rolling path 13. The opposite leg 12 is also inclined at an angle α in the opposite direction in accordance with the lead angle. That is, the pair of leg portions 12 of the return pipe 10 are arranged in the tangential direction of the spiral load ball rolling path 13. Since the ball 9 is picked up and returned in the tangential direction of the spiral loaded ball rolling path 13, no excessive force is applied to the ball 9.

  FIG. 4 shows the circulation trajectory of the ball. 4 (A) shows the circulation track as seen from the axial direction of the screw shaft, FIG. 4 (B) shows a plan view of the circulation track, FIG. 4 (C) shows the circulation track as seen from the side of the return pipe, FIG. 4 (D) shows the circulation trajectory as seen from the side of the screw shaft. A spiral load ball rolling path 13 is formed between the ball rolling groove 7 a of the screw shaft 7 and the load ball rolling groove 8 a of the nut 8. Inside the return pipe 10, an unloaded ball return passage 19 is formed as an unloaded rolling element return passage that connects one end and the other end of the loaded ball rolling groove 8 a of the nut 8. The no-load return passage 19 is composed of a combination of a linear track and an arc track. In the central portion 11 of the return pipe 10, a straight passage 11c extending linearly inside is formed. Each of the pair of leg portions 12 is formed with an arc passage 12b that is continuous with the linear passage 11c and bends in an arc shape, and a linear passage 12c that extends linearly from the end of the arc passage 12b. At the junction between the loaded ball rolling path 13 and the no-load return path 19, the tangential direction of the circulation track is set continuously so that the ball moves smoothly. Since the screw shaft 7 has a lead, as shown in FIG. 3C, the center lines of the straight passages 12c in the pair of legs 12 of the return pipe 10 are inclined at an angle α to each other in the opposite direction from the center line. ing.

  When the screw shaft 7 is rotated relative to the nut 8, the ball 9 rolls along the load ball rolling path 13. The ball 9 that has rolled to one end of the loaded ball rolling path 13 is scooped up into the return pipe 10, passes through the unloaded ball return path 19, and then returned to the other end of the loaded ball rolling path 13 several turns before. While the screw shaft 7 is rotating with respect to the nut 8, the ball 9 circulates infinitely through a ball circulation path constituted by the loaded ball rolling path 13 and the unloaded ball return path 19.

  As shown in FIG. 5 and FIG. 6, the return pipe 10 is formed by adhesively joining the divided pieces 21 and 22 divided into two. In addition, in this figure, since it has focused on the division | segmentation pieces 21 and 22 of the return pipe 10, the scooping part 12d and the extension part 11a are abbreviate | omitted. As described above, the scooping portion 12 d (see FIG. 3) is formed at the tip of the leg portion 12 of the return pipe 10. If it divides | segments to the front-end | tip of the leg part 12, since the complicated shaped scooping part 12d will be divided | segmented, the continuity of the scooping part 12d shape will be prevented. For this reason, in this embodiment, the tip of the leg portion 12 is not divided. The two divided pieces 21 and 22 have the same shape so that the molds can be shared by the divided pieces 21 and 22.

  The joint surfaces 21a and 22a of the respective divided pieces 21 and 22 are formed in an uneven shape in which the convex portions 21b and 22b and the concave portions 21c and 22c are repeated. The pair of divided pieces 21 and 22 are coupled in a state where the concave and convex shapes of the joint surfaces 21a and 22a are engaged with each other. As shown in FIG. 6, the top surfaces 25 of the convex portions 21 b and 22 b and the bottom surfaces 26 of the concave portions 21 c and 22 c are located in a plane parallel to the center line of the return pipe 10 and the center line of the central portion 11. And a predetermined distance L from the plane P1 including the center line of the leg 12. The side surfaces 27 of the convex portions 21 b and 22 b are located in a plane P <b> 2 that is orthogonal to the center line of the return pipe 10.

  Strictly speaking, as shown in FIG. 4C, the center line of the pair of leg portions 12 is inclined at an angle α in the opposite direction with respect to the center line of the center portion 11 (return in FIG. 7). (See also the plan view of the pipe 10), the plane including the center line of the one leg 12 and the center line of the center part 11, and the plane including the center line of the other leg part 12 and the center line of the center part 11 It is tilted by 2α. The top surfaces 25 of the convex portions 21b and 22b and the bottom surfaces 26 of the concave portions 21c and 22c are separated from either plane inclined by 2α.

  Each of the divided pieces 21 and 22 is manufactured by injection molding a resin. The tip of the leg portion 12 that is not divided is manufactured using a slide mold. For example, a slide mold that forms the tip of the leg is inserted into the mold, and resin is injection-molded into a cavity in the mold. After opening the mold, the slide mold is slid in the direction of the center line of the leg portion 12, and the slide mold is removed from the divided piece.

  After resin-molding the divided pieces 21 and 22, an adhesive is applied to the joint surfaces 21 a and 22 a of the divided pieces 21 and 22, and the concave portion 22 c of the other divided piece 22 is meshed with the convex portion 21 b of one divided piece 21. These are adhesively bonded. Here, not only the top surface 25 of the convex portion 21b of the one divided piece 21 and the bottom surfaces 26 of the concave portion 21c of the other divided piece 22, but also the side surfaces 27 of the convex portions 21b and 22b are adhesively bonded. As a method of adhesively bonding the divided pieces, adhesive bonding by welding or an adhesive sheet may be used.

  According to this embodiment, since the bonding area can be increased by making the joining surfaces 21a and 22a uneven, the bonding strength can be increased. In addition, as shown in FIG. 8, when the ball screw is overloaded and a force F for opening the return pipe 10 is applied, the side surfaces 27 of the convex portions 21 b and 22 b of the divided pieces 21 and 22 are applied. Shear τ works. Since the force F for opening the return pipe 10 is received as the shearing force τ by the side surfaces 27 of the convex portions 21b and 22b that are adhesively bonded, the large force F for opening the return pipe 10 can be resisted.

  The inner wall of the return pipe 10 on a plane including the center line of the central part 11 and the center line of the leg part 12 becomes a part where the ball 9 can easily push the return pipe 10 when it is clogged. Since the joint surfaces (the top surfaces 25 of the convex portions 21b and 22b and the bottom surfaces 26 of the concave portions 21c and 22c) are separated from the portion where the ball 9 is easy to push the return pipe 10, the force to open the return pipe 10 is difficult to work. .

  In addition, this invention is not restricted to the said embodiment, In the range which does not change the summary of this invention, it can change variously. For example, the top surface of the convex portion and the bottom surface of the concave portion may not be parallel to the center of the return pipe but may be inclined like a saw blade. Further, rollers can be used as rolling elements instead of balls.

7 ... Screw shaft 7a ... Ball rolling groove (rolling element rolling groove)
8 ... Nut 8a ... Loaded ball rolling groove (Loaded rolling element rolling groove)
9 ... Ball (rolling element)
DESCRIPTION OF SYMBOLS 10 ... Return pipe 11 ... Center part 12 ... Leg part 13 ... Load ball rolling path (Load rolling element rolling path)
19: No-load ball return path (no-load rolling element return path)
21, 22 ... split pieces 21 a, 22 a ... joint surfaces 21 b, 22 b ... convex parts 21 c, 22 c ... concave part 25 ... top surface 26 of convex part ... bottom face 27 of concave part ... side surface of convex part

Claims (2)

A screw shaft having a spiral rolling element rolling groove formed on the outer peripheral surface, a nut having a spiral load rolling element rolling groove facing the rolling element rolling groove on the inner peripheral surface, and a central portion And a pair of legs bent with respect to the center, a return pipe connecting one end and the other end of the load rolling element rolling groove of the nut, the rolling element rolling groove of the screw shaft, and the The nut of the screw shaft is arranged in a rolling element circulation path composed of a loaded rolling element rolling path between the nut and the loaded rolling element rolling groove and an unloaded rolling element return path in the return pipe. A rolling element screw device comprising: a plurality of rolling elements that circulate in association with relative rotation with respect to
The return pipe is formed by adhesively bonding two divided pieces,
Each divided piece has a joint surface formed in a concavo-convex shape in which convex portions and concave portions are repeated,
The rolling element screw device, wherein a side surface of the convex portion is located in a plane orthogonal to a center line of the return pipe.   The top surface of the convex portion and the bottom surface of the concave portion are located in a plane parallel to the center line of the return pipe, and the top surface of the convex portion and the bottom surface of the concave portion are the center line of the central portion and The rolling element screw device according to claim 1, wherein the rolling element screw device is separated from a plane including a center line of the leg portion.

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