JP5058095B2 - Screw device and motion guide device - Google Patents

Description

  The present invention relates to a screw device in which a plurality of rolling elements are interposed between a screw shaft and a nut so that the rolling movement is possible, and a movement in which a plurality of rolling elements are interposed between a raceway member and a moving member. The present invention relates to a guide device.

  A ball screw is a mechanical element that converts rotational motion into linear motion. In order to reduce the friction when rotating the screw shaft relative to the nut, between the ball rolling groove on the outer peripheral surface of the screw shaft and the loaded ball rolling groove on the inner peripheral surface of the nut facing this A plurality of balls are interposed so as to allow rolling motion.

  In order to circulate the ball that rolls between the screw shaft and the nut, a return pipe is attached to the nut as a circulating member. The return pipe is formed with a no-load return path that connects one end and the other end of the spiral loaded ball rolling groove of the nut. The ball that rolls between the ball rolling groove of the screw shaft and the loaded ball rolling groove of the nut rolls up to one end of the loaded ball rolling groove of the nut, and is then rolled up into the unloaded return path of the return pipe, After passing through the no-load return path of the return pipe, it is returned to the other end of the loaded ball rolling groove of the nut (see, for example, Patent Document 1).

  In 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 rolls while receiving a compressive load. On the other hand, in the unloaded return path of the return pipe, there is play around the ball, and the ball moves while being pushed by the succeeding ball without receiving a load, and moves to the loaded ball rolling path.

  On the other hand, the motion guide device is a mechanical element that guides a linear motion or a curved motion of a moving body. Rolling motion is possible between the rolling element rolling part of the track rail and the loaded rolling element rolling part of the moving block in order to reduce friction when the moving block moves linearly or curvedly with respect to the track rail. A plurality of rolling elements such as balls and rollers are interposed (see, for example, Patent Document 2).

The moving block is provided with a circuit-like circulation path for circulating the rolling elements. The circulation path includes a rolling element rolling path between the rolling element rolling part of the track rail and the loaded rolling element rolling part of the moving block, a no-load return path extending in parallel with the loaded rolling element rolling part of the moving block, and It is comprised from the U-shaped direction change path which connects the both ends of the load rolling-element rolling part of a moving block, and the both ends of the no-load return path of a moving block. The rolling element rolling between the rolling element rolling part of the track rail and the loaded rolling element rolling part of the moving block rolls to one end of the loaded rolling element rolling part of the moving block, and then a U-shaped direction change path. Can be crawled up. The rolling elements that have passed through the unloaded return path of the moving block are returned to the other end of the loaded rolling element rolling part of the moving block from the opposite direction change path.
JP 2003-194178 A JP 2008-89045 A

  There are two types of circulation paths of rolling elements, a load area and a no-load area, in both the conventional ball screw and the motion guide device. And the rolling element which moves on the no-load return path of a no-load area | region transfers to the load rolling-element rolling path of a load area, being pushed by the subsequent rolling element.

  However, as shown in FIG. 33, when the rear rolling element 72 in the no-load return path 71 pushes the front rolling element, the rolling element 72 meanders in the no-load return path 71. For this reason, it becomes difficult for the rolling element 72 to smoothly move from the no-load return path 71 to the loaded rolling element rolling path 73.

  Therefore, an object of the present invention is to provide a screw device and a motion guide device that can smoothly move a rolling element from a no-load region to a load region.

The present invention will be described below.
In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a screw shaft having a spiral rolling element rolling groove on an outer peripheral surface, and facing the rolling element rolling groove of the screw shaft on an inner peripheral surface. A nut having a spiral loaded rolling element rolling groove, and an unloaded return path having a cross-sectional shape connected to one end and the other end of the loaded rolling element rolling groove of the nut and surrounding the rolling element Circulation composed of a circulating member, 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 the unloaded return path of the circulating member A plurality of rolling elements arranged in a path so as to be able to circulate, and facing the rolling element rolling groove of the screw shaft at the end of the circulation member in the length direction of the no-load return path , restraining part is provided sandwiching the rolling elements between the rolling element rolling groove of the screw shaft, it said循By providing the restricting portion of the member, the intermediate region is provided between the unloaded return path and the loaded rolling member rolling passage, by relatively rotating the screw shaft relative to the nut, the A rolling element sandwiched between the restraining portion of the circulation member and the rolling element rolling groove of the screw shaft is drawn into the loaded rolling element rolling path or the no-load return path, and the rolling element is a ball, The cross-sectional shape of the loaded rolling element rolling groove of the nut is formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball, and the restraining portion of the circulation member has the A cross-sectional shape in a plane perpendicular to the traveling direction of the ball is a screw device formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball .

The invention according to claim 2 is a screw shaft having a spiral rolling element rolling groove on the outer peripheral surface, and a spiral load rolling element rolling facing the rolling element rolling groove of the screw shaft on the inner peripheral surface. A nut having a running groove, a circulating member connected to one end and the other end of the loaded rolling element rolling groove of the nut and having a cross-sectional unloaded return path surrounding the circumference of the rolling element, and the screw shaft Circulation is arranged in a circulation path composed of a loaded rolling element rolling path between the rolling element rolling groove and the loaded rolling element rolling groove of the nut, and the no-load return path of the circulation member. A plurality of rolling elements, and the end of the circulation member in the length direction of the unloaded return path is opposed to the rolling element rolling groove of the screw shaft, and the rolling element of the screw shaft rolling restraining portion sandwiching the rolling elements between the grooves is provided, providing the restraining portion of the circulation member And by, said intermediate region is provided between the unloaded return path and the loaded rolling member rolling passage, said rolling elements between said restraining portion of the rolling member rolling groove and the circulation member of the screw shaft Is less than or not present in the unloaded return path , the rolling element is a ball, and the sectional shape of the loaded rolling element rolling groove of the nut is the ball. Formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the circular member, and the cross-sectional shape of the restraint portion of the circulating member in a plane perpendicular to the moving direction of the ball is the ball The screw device is formed in a Gothic arch groove shape including two circular arc-shaped curves having a radius of curvature larger than the radius of .

According to a third aspect of the present invention, in the screw device according to the first or second aspect , the restraint portion of the circulation member is configured such that play of the ball gradually decreases toward the load rolling element rolling path. It is characterized by extending linearly.

According to a fourth aspect of the present invention, in the screw device according to any one of the first to third aspects, the no-load return path of the circulation member is connected to the restraining portion and viewed from the axial direction of the nut. A curved path is provided in which a center line is a convex arcuate curve toward the screw shaft.

  According to the present invention, a restraint portion is provided between the no-load return path in the no-load area and the load rolling element rolling path in the load area, so that an intermediate area with less play is provided. In this intermediate region, the rolling element is drawn into the loaded rolling element rolling path or the unloaded return path not by being pushed into the subsequent rolling element but by the rotation of the screw shaft. For this reason, it is possible to smoothly move the rolling elements from the no-load region to the load region or from the load region to the no-load region.

  FIG. 1 shows a perspective view of a ball screw according to a first embodiment of the present invention. The ball screw has a screw shaft 1 in which a ball rolling groove 1a, which is a spiral rolling element rolling groove, is formed on the outer peripheral surface, and a helical load rolling element rolling that faces the ball rolling groove 1a on the inner peripheral surface. A plurality of nuts 2 in which a loaded ball rolling groove 2a, which is a running groove, is formed, and a ball rolling groove 1a of the screw shaft 1 and a loaded ball rolling groove 2a of the nut 2 are interposed so as to allow rolling motion. And a ball 3 (see FIG. 4).

  A ball rolling groove 1a of a predetermined lead is formed on the outer peripheral surface of the screw shaft 1 by grinding or rolling. As shown in FIG. 4, the ball rolling groove 1 a is formed in a Gothic arch groove shape including two arcs 4 having a radius slightly larger than the radius of the ball 3. The centers C1 of the two arcs are located at a position away from the center C2 of the ball 3. The ball 3 contacts the ball rolling groove 1a having a Gothic arch groove shape at two points. The contact angle θ between the line L connecting the center C2 of the ball 3 and the bottom 5 of the gothic arch groove, and the line connecting the contact point 6 between the arc 4 and the ball 3 and the center C2 of the ball 3 is, for example, 40 to Set to 50 degrees. The ball rolling groove 1a is ground after being heat-treated. Arc-shaped chamfers 7 may be formed on both side edges of the ball rolling groove 1a, or a relief groove serving as a relief during grinding may be formed on the bottom 5 of the gothic arch groove.

  FIG. 2 shows a perspective view of the nut 2 with the screw shaft 1 removed. A through hole 2 e through which the screw shaft 1 passes is formed in the nut 2. On the inner peripheral surface of the nut 2, a spiral loaded ball rolling groove 2a having a predetermined lead is formed by grinding. As shown in FIG. 4, the cross-sectional shape of the loaded ball rolling groove 2 a is formed in a Gothic arch groove shape including two arcs 4 having a radius slightly larger than the radius of the ball 3. The Gothic arch groove shape is the same as the ball rolling groove 1 a of the screw shaft 1. The loaded ball rolling groove 2a is ground and then heat-treated.

  A flange 2b for attaching the nut 2 to the other machine part is formed at one end of the nut 2 in the axial direction. A flat chamfered portion 2 c is formed on the outer peripheral surface of the nut 2. A circulation member 8 is attached to the flattening portion 2c. The circulation member 8 is formed with a no-load return path 10 (see FIG. 6) connected to one end and the other end of the loaded ball rolling groove of the nut 2.

  FIG. 5 shows a perspective view of the nut with the circulation member 8 removed. Balls rolling on the loaded ball rolling path 12 between the ball rolling groove 1a of the screw shaft 1 and the loaded ball rolling groove 2a of the nut 2 are provided at both ends in the length direction of the unloaded return path 10 of the circulation member 8. A pair of scooping portions 14 that scoop up 3 into the no-load return path 10 is formed. A pair of through holes 15 that penetrate from the outer surface to the inner surface of the nut 2 and into which the pair of raised portions 14 of the circulation member 8 are fitted are opened in the flattening portion 2 c of the nut 2. The through hole 15 is a long hole extending along the load ball rolling groove 2 a of the nut 2. A notch groove 16 extending in the axial direction of the nut 2 is formed between the pair of through holes 15. The notch groove 16 has a flat groove bottom 16a and a pair of flat inner wall surfaces 16b that rise from the groove bottom 16a and face each other. The groove bottom 16 a is parallel to the plane of the chamfered portion 2 c and is located in a plane parallel to the axis of the nut 2. The inner wall surface 16b is located in a plane parallel to the axis of the nut 2 and is orthogonal to the plane including the groove bottom 16a.

  The circulating member 8 is fitted into the through hole 15 and the notch groove 16 of the nut 2. The circulation member 8 includes a pair of end portions 8a including a pair of raised portions 14 and a main body portion 8b between the pair of end portions 8a. The end portion 8a is elongated along the load ball rolling groove 2a of the nut 2. The cross-sectional shape of the end portion 8 a matches the cross-sectional shape of the through hole 15. The main body portion 8 b extends in the axial direction of the nut 2. The cross-sectional shape of the main body portion 8b is a combination of a square and a semicircle. A pair of flat outer wall surfaces 17 corresponding to the inner wall surface 16b of the notch groove 16 is formed on the side surface of the main body portion 8b. The bottom surface 19 of the main body portion 8 b is formed in a plane corresponding to the groove bottom 16 a of the notch groove 16.

  The circulation member 8 is formed by combining a pair of divided bodies 18 that are divided into two along the no-load return path 10. Reference numeral 24a in the figure is a dividing plane. The pair of divided bodies 18 are formed in the same shape, and are manufactured by injection molding a resin in a common mold. The pair of divided bodies 18 are joined by welding such as laser welding, welding, or adhesion.

  As shown in FIG. 2, when the circulating member 8 is attached to the nut 2, the pair of end portions 8 a of the circulating member 8 are fitted into the pair of through holes 15 of the nut 2, and the main body portion 8 b of the circulating member 8 is the nut. It fits into the two notch grooves 16. As shown in FIG. 3, the upper portion 20 of the main body portion 8 b of the circulation member 8 protrudes from the notch groove 16. The upper portion 20 of the main body portion 8b is pressed by the pressing member 21. The presser member 21 includes a main body presser 21a bent in a U shape in accordance with the upper portion of the main body portion 8b, and mounting seats 21b provided on both sides of the main body presser 21a. The holding member 21 is manufactured by bending a metal plate. A through hole 21c is opened in the mounting seat 21b. The presser member 21 is attached to the nut 2 by passing the bolt through the through hole 21 c and screwing the bolt into the screw hole of the nut 2. The circulation member 8 is sandwiched between the pressing member 21 and the notch groove 16 of the nut 2 and is fixed to the nut 2.

  As shown in FIG. 5, the circulation member 8 fits into the notch groove 16 of the nut 2, and the bottom surface 19 of the main body portion 8 b of the circulation member 8 contacts the groove bottom 16 a of the notch groove 16 of the nut 2. The position of the circulation member 8 in the X direction is positioned on a plane orthogonal to the axis of the nut 2. Further, when the outer wall surface of the main body portion 8 b of the circulation member 8 contacts the inner wall surface 16 b of the notch groove 16 of the nut 2, the position of the circulation member 8 on the plane is positioned in the Y direction. Then, the end portion 8 a of the circulation member 8 is fitted into the through hole 15 of the nut 2, whereby the position of the circulation member 8 in the Z direction in the axial direction of the nut 2 is positioned. In other words, the circulating member 8 can be accurately positioned with respect to the nut 2, and consequently the raised portion 14 of the circulating member 8 can be accurately positioned with respect to the load ball rolling groove 2 a of the nut 2. Thereby, the ball 3 can be smoothly moved between the no-load return path 10 and the loaded ball rolling path 12. By sandwiching the circulation member 8 between the inner wall surfaces 16b of the notch groove 16, it is possible to prevent the divided surface 24a of the divided circulation member 8 from being opened.

  FIG. 6 shows the ball circulation path of the ball screw. A spiral load ball rolling path 12 is formed between the ball rolling groove 1 a of the screw shaft 1 and the load ball rolling groove 2 a of the nut 2. One end and the other end of the loaded ball rolling path 12 are connected by a no-load return path 10 so that the ball 3 moving from one end to the other end of the loaded ball rolling path 12 can be circulated. A large number of balls 3 are arranged and accommodated in the circulation path constituted by the loaded ball rolling path 12 and the no-load return path 10. As described above, the no-load return path 10 is formed in the circulation member 8. The no-load return path 10 has a structure in which the number of turns of the load ball rolling path 12 is close to an integer such as 2, 3, 4, or the like.

  FIG. 7 shows the center line of the circulation path seen from the side of the nut 2 (orbit of the center of the ball 3), and FIG. 8 shows the center line of the unloaded return path 10 seen from the axial direction of the nut 2 (of the ball 3). Center orbit). The no-load return path 10 can be divided into three sections: a curved path 22, a radial path 23, and an axial path 24. As shown in FIG. 8, the curved path 22 has a ball 3 that moves on the circular load ball rolling path 12 as seen from the axial direction of the nut 2, and the center of the path 3 has a convex arc toward the screw shaft 1. Move to become. In the conventional ball screw, the ball 3 is scooped up in the tangential direction of the circular load ball rolling path 12 as viewed from the axial direction of the nut 2. On the other hand, in the ball screw of the present embodiment, the ball 3 is scooped up along a circular arc track like a linear guide. In the curved path 22, the ball 3 is scooped up along the arcuate curved surface of the scooping portion 14. The tangential direction continues at a connection point P1 (lifting point) between the load ball rolling path 12 and the curved path 22 so that the ball 3 moves smoothly from the loaded ball rolling path 12 to the curved path 22.

  As shown in FIG. 7, the center line of the curved passage 22 is orthogonal to the axis 2 f of the nut 2 when viewed from the side of the nut 2. As shown in FIG. 8, the curved passage 22 is connected to a radial passage 23 that moves the ball 3 in the radial direction when viewed from the axial direction of the nut 2. The center line of the radial passage 23 extends in the radial direction of the nut 2 when viewed from the axial direction of the nut 2. As shown in FIG. 7, the radial passage 23 is bent backward by 90 degrees and then connected to the axial passage 24 parallel to the axis 2 f of the nut 2. The axial passage 24 moves the ball 3 to the nut 2 parallel to the axis. The ball 3 that has moved in the axial path 24 is returned to the loaded ball rolling path 12 again via the opposite radial path 23 and curved path 22. As shown in FIG. 8, the curved path 22 on the near side and the curved path 22 on the far side are formed symmetrically with respect to the center line 2 g of the nut 2.

  FIG. 9 shows a perspective view of the unloaded return path 10 developed on the screw shaft 1. The unloaded return path 10 of the circulating member 8 is provided with an axial passage 24 parallel to the axis of the nut 2, and the ball 3 is circulated in parallel with the axis of the nut 2, whereby the unloaded return path viewed from the axial direction of the nut 2. Ten inlets and outlets can be brought closer to the same position. For this reason, the number of turns of the load ball rolling path 12 can be made close to an integer. Further, since the raising portion 14 of the curved path 22 of the circulation member 8 like the linear guide raises the ball 3 in an arc shape, the number of turns of the load ball rolling path 12 can be made closer to an integer, and the smoothness of the ball 3 can be improved. Circulation is also possible.

  10 and 11 show the screw shaft 1 and the circulation member 8. A no-load return path 10 developed on the screw shaft 1 is formed in the circulation member 8. The no-load return path 10 of the circulation member 8 is formed in a circular shape with a closed curve surrounding the periphery of the ball 3. The unloaded return path 10 of the circulation member 8 is provided with an inlet 10a and an outlet 10b. The inlet 10 a is connected to one end of the load ball rolling path 12, and the outlet 10 b is connected to the other end of the load ball rolling path 12. The circulation member 8 is divided into two along the center line of the no-load return path 10. As shown in FIG. 10, the axial passage 24 of the no-load return path 10 is divided into two by a split surface 24 a parallel to the axis of the screw shaft 1, and as shown in FIG. 11, The radial passage 23 and the curved passage 22 are divided into two by a dividing surface 24b along the center line when viewed from the axial direction of the screw shaft 1. The lifting portion 14 is formed in each of the divided parts so as not to be divided by the lifting portion 14 of the curved passage 22.

  12 and 13 are detailed views of the circulation member 8 attached to the nut 2. In the curved path 22 of the circulation member 8, a lifting part 14 that scoops up the ball 3 rolling on the loaded ball rolling path 12 is formed. As shown in FIG. 13, when viewed from the axial direction of the screw shaft 1, the back surface 14 a of the lifting portion 14 is parallel to the center line of the radial passage 23. An arcuate curved surface is formed on the inner peripheral surface 14 b of the lifting portion 14. The raised portion 14 gradually increases in thickness toward the center of the screw shaft 1. By increasing the thickness of the lifting portion 14, the strength of the lifting portion 14 with which the ball 3 collides can be increased.

  A restraining portion 28 that faces the ball rolling groove of the screw shaft 1 is formed at the end of the circulation member 8 in the length direction of the unloaded return path 10. The restraining part 28 becomes a part connected to the load ball rolling groove 2 a of the nut 2. The ball 3 is sandwiched between the restraining portion 28 and the rolling element rolling groove of the screw shaft 1. The cross-sectional shape of the restraining portion 28 in the plane orthogonal to the traveling direction of the ball 3 is formed in a Gothic arch groove shape that matches the cross-sectional shape of the loaded ball rolling groove 2 a of the nut 2. The play of the ball 3 sandwiched between the ball rolling groove 1a of the screw shaft 1 and the restraining portion 28 of the circulation member 8 is smaller than the play of the ball 3 in the unloaded return path 10 having a closed curved cross section, or not exist. The restraining portion 28 of the circulation member 8 extends linearly in the traveling direction of the ball 3 so that the play of the ball 3 gradually decreases toward the loaded ball rolling path 12.

  The cross-sectional shape of the raised portion 14 of the circulating member 8 in a plane perpendicular to the traveling direction of the ball 3 is formed into a circular arc groove shape formed of a single arc having a radius of curvature slightly larger than the radius of the ball 3. Is done. The cross-sectional shapes of the radial passage 23 and the axial passage 24 of the circulation member 8 are formed in a circular shape having a radius slightly larger than the radius of the ball 3.

  14 and 15 show changes in the cross-sectional shape of the no-load return path 10 of the circulation member 8. In the region from (1) to (2), that is, in the region of the load ball rolling path 12 and the restraining portion 28 of the circulating member 8, these cross-sectional shapes are formed in a Gothic arch groove shape. In the region from (2) to (3), that is, the region of the curved passage 22, the outer cross-sectional shape of the curved passage 22 gradually changes from a Gothic arch groove shape matched to the restraining portion 28 to a circular arc groove shape. . The cross-sectional shape of the raised portion 14 inside the curved path 22 is formed in a circular arc groove shape. In the region from (3) to (4), that is, in the region of the radial passage 23 and the axial passage 24, the cross-sectional shape is formed in a circular shape. The cross-sectional shape of the no-load return path 10 in the region from (4) to (5) is the same as the region from (2) to (3). The cross-sectional shape of the unloaded return path 10 in the region from (5) to (6) is the same as the region from (1) to (2).

  FIG. 16 shows a detailed cross-sectional view of the curved passage 22 which is a region from (2) to (3). In the curved passage 22, the cross-sectional shape on the nut 2 side (restraint portion 28 side) is formed in a Gothic arch groove shape composed of two arcs R1. On the other hand, the cross-sectional shape on the screw shaft 1 side (the raised portion 14 side) is formed into a circular arc groove shape composed of a single arc R2.

  As shown in FIG. 13, in the loaded ball rolling path 12, the ball 3 is sandwiched between the ball rolling groove 1 a of the screw shaft 1 and the loaded ball rolling groove 2 a of the nut 2 and receives a compressive load. While exercising rolling. On the other hand, in the no-load return passage 10 of the circulation member 8, there is a slight play between the ball 3 and the no-load return rolling path 10, and the ball 3 is pushed by the subsequent ball 3 without being loaded. Moving.

  In the conventional ball screw, there are two types of circulation paths of the ball 3, that is, a no-load return path 10 in the no-load region and a load ball rolling path 12 in the load region. On the other hand, in the ball screw of this embodiment, a restraint portion is provided between the no-load return path 10 in the no-load area and the load ball rolling path 12 in the load area so that an intermediate area with less play is provided. It is done. In this intermediate region, the ball 3 is drawn into the loaded ball rolling path 12 not by being pushed into the subsequent ball 3 but by the rotation of the screw shaft 1. For this reason, the ball 3 can be smoothly moved from the no-load region to the load region. Further, when the ball 3 moves from the loaded ball rolling path 12 to the unloaded return path 10, the ball 3 is guided between the restraining portion 28 of the circulation member 8 and the screw shaft 1. Can be moved smoothly inward.

  Further, by forming the cross-sectional shape of the restraint portion 28 of the unloaded return path 10 of the circulation member 8 into a Gothic arch groove shape that matches the cross-sectional shape of the loaded ball rolling groove 2a of the nut 2, the restraint portion 28 is correctly aligned. The ball 3 can be smoothly moved to the loaded ball rolling groove 2a. By making the play of the ball 3 in the restricting portion 28 gradually decrease toward the load ball rolling path 12, the ball 3 can be moved more smoothly.

  As shown in FIG. 17, in the conventional ball screw, the cross-sectional shape of the unloaded return path 10 of the circulation member is formed in a circular arc groove shape. On the other hand, the cross-sectional shape of the load ball rolling groove 2a of the nut 2 is formed in a Gothic arch groove shape. For this reason, it is necessary to machine a chamfer 29 for making the cross-sectional shape continuous at the joint of the load ball rolling groove 2a of the nut 2. On the other hand, by forming the cross-sectional shape of the restraining portion 28 of the circulation member 8 in a Gothic arch groove shape as in the present embodiment, the ball 3 can be moved to the no-load return path 10 without chamfering the nut 2. Can be easily transferred to the load ball rolling groove 2a.

  As shown in FIG. 13, the ball 3 collides with the lifting portion 14. If the cross-sectional shape of the raised portion 14 is formed in a Gothic arch groove shape, an edge is likely to occur at the tip of the raised portion 14 with which the ball 3 collides. By forming the cross-sectional shape of the raised portion 14 into a circular arc groove shape and rounding the tip of the raised portion into an arc shape, it is possible to prevent an edge from occurring at the distal end of the raised portion 14. In addition, by forming the cross-sectional shapes of the radial passage 23 and the axial passage 24 of the no-load return passage 10 in a circular shape, it becomes easy to manufacture the divided body 18 using a mold.

  FIG. 18 shows a circulation path for realizing a complete integer winding. When viewed from the axial direction of the nut 2, a load ball rolling of the center S 1 of the screw shaft 1 and the nut 2 from a line L 1 (center line) connecting the center S 1 of the screw shaft 1 and the center line of the radial passage 23 of the circulation member 8. On the circular arc-shaped track at the center of the ball 3 in the loaded ball rolling path 12 up to the line L2 connecting the boundary B1 (see FIG. 13, circulation start point) between the running groove and the unloaded return path 10 of the circulating member 8 Is set to be larger than 0 and not more than 1.5 times the diameter Da of the ball 3. The shorter the distance α is, the more difficult it is to turn. Therefore, the center line of the curved passage 22 is designed to return to the center line L1 of the nut 2 again after exceeding the center line L1 of the nut 2. May be.

  If the distance α is 0, the number of balls 3 that can receive a load is equal to the number of balls 3 that can receive a load at the position where the balls 3 are scooped up when viewed from the axial direction of the screw shaft 1. One more than the other 12 parts. On the other hand, when the distance α is 1 · Da or more, the number of the balls 3 that can receive a load at the position where the balls 3 are scooped up is one less than the other portions. However, since the distance to turn becomes long, it becomes easy to turn the ball 3. The distance α is set to be larger than 0 and 1.5 times or less of the ball diameter in consideration of approaching the integer winding and the ease of turning of the ball 3. By setting the arc-shaped distance α to 0.4 times or more and 0.6 times or less, preferably 0.5 times the ball diameter, as shown in FIG. 19, when viewed from the axial direction of the screw shaft 1, The two balls 3 on the near side and the far side can be arranged so as to come into contact with each other, and the balls 3 can be arranged without gaps on the load ball rolling path 12. In other words, the ball 3 is beaten from the load ball rolling path 12 on the near side, and at the same time, the ball 3 returns to the load ball rolling path 12 on the far side. Therefore, a screw device that can realize complete integer winding is obtained.

  FIG. 20 is a perspective view of a ball screw according to the second embodiment of the present invention. Also in the ball screw of this embodiment, the number of turns of the load ball rolling path 33 is close to an integer. The point that the ball rolling groove 31a is formed on the screw shaft 31 and the load ball rolling groove 32a is formed on the nut 32 is the same as the ball screw of the first embodiment.

  21 and 22 show the nut 32 to which the circulation member 34 is attached. The circulation member 34 is formed with a no-load return path 35 connected to one end and the other end of the load ball rolling path 33. The no-load return path 35 includes a curved path 36 (see FIG. 22) that scoops up the ball moving on the loaded ball rolling path 33 along an arcuate path, and a radial path 37 that moves the scooped ball in the radial direction. (See FIG. 22) and an axial passage 38 (see FIG. 21) for moving the ball parallel to the axis of the nut 32.

  As shown in FIG. 23, the circulation member 34 is formed by joining a pair of divided bodies 39 that are divided into two along the axis of the nut 32.

  As shown in FIG. 24, the nut 32 is formed with a pair of through holes 32b that penetrate from the outside to the inside. The pair of through holes 32 b are arranged in the axial direction of the nut 32.

  25 and 26 are detailed views of the circulation member 34. FIG. Each of the pair of divided bodies 39 is formed with a lifting portion 40 that scoops up a ball moving on the loaded ball rolling path 33 along an arcuate path.

  FIG. 27 shows a detailed view of the lifting unit 40. A constraining portion 42 is formed at a portion of the end of the circulation member 34 in the length direction of the no-load return path 35 connected to the load ball rolling groove 32a of the nut 32. A ball 41 is sandwiched between the restraining portion 42 and the screw shaft 31. The cross-sectional shape of the restraint portion 42 is formed in a Gothic arch groove shape that matches the cross-sectional shape of the load ball rolling groove 32 a of the nut 32. On the other hand, the cross-sectional shape of the raised portion 40 of the circulation member 34 is formed in a circular arc groove shape having a radius larger than the radius of the ball 41.

  28 and 29 show the ball 41 circulating in the circulation path. When the screw shaft 31 is rotated relative to the nut 32, the ball 41 rolls along the loaded ball rolling path 33 between the screw shaft 31 and the nut 32. The ball 41 that has moved to one end of the load ball rolling path 33 is scooped up along the arcuate track by the scooping portion 40 of the circulation member 34. The ball 41 that has passed through the curved passage 36, the radial passage 37, and the axial passage 38 of the circulation member 34 is returned again to the loaded ball rolling passage 33 via the opposite radial passage 37 and the curved passage 36. When the ball 41 is returned to the load ball rolling path 33, the ball 41 sandwiched between the screw shaft 31 and the restraining portion 42 of the circulation member 34 is drawn into the load ball rolling path 33 by the rotation of the screw shaft 31. For this reason, the ball 41 can be moved smoothly.

  FIG. 30 is a perspective view of the motion guide device according to the third embodiment of the present invention. The motion guide device (linear guide) includes a track rail 51 that is a track member and a moving block 52 that is a moving member that is assembled to the track rail 51 so as to be relatively linearly movable. In the track rail 51, a ball rolling groove 51a which is a rolling element rolling portion is formed.

  The moving block 52 includes a metal moving block main body 53 and end plates 54 that are resin lid members provided at both ends of the moving block main body 53 in the moving direction. The moving block main body 53 is formed with a loaded ball rolling groove 53a which is a loaded rolling element rolling portion facing the ball rolling groove 51a of the track rail 51, and is unloaded parallel to the loaded ball rolling groove 53a. A return path 55 is formed. The end plate 54 is formed with a U-shaped direction change path 56 (see FIG. 31) that connects the end of the loaded ball rolling groove 53a and the end of the no-load return path 55.

  As shown in FIG. 31, the loaded ball rolling path 57, the unloaded return path 55, and the end plate 54 between the ball rolling groove 51 a of the track rail 51 and the loaded ball rolling groove 53 a of the moving block main body 53. A plurality of balls 58 are arranged in a circuit-like circulation path composed of the direction change paths 56 so as to be circulated. The balls 58 are held in series by a retainer band 59. A spacer 60 for preventing contact between the balls 58 is interposed between the balls 58.

  A restraining portion 62 that faces the ball rolling groove 51 a of the track rail 51 is provided at an end portion in the length direction of the U-shaped direction changing path 56 of the end plate 54. A ball 58 is sandwiched between the ball rolling groove 51 a of the track rail 51 and the restraining portion 62 of the end plate 54. The play of the ball 58 between the ball rolling groove 51 a of the track rail 51 and the restraining portion 62 of the end plate 54 is smaller than or not present than the play of the ball 58 in the direction change path 56 of the end plate 54.

  As shown in FIG. 32, the restraining portion 62 extends linearly toward the load ball rolling groove 53 a of the moving block main body 53. The play of the ball 58 in the restraining portion 28 is gradually set smaller toward the loaded ball rolling groove 53 a of the moving block main body 53.

  By moving the moving block 52 relatively linearly with respect to the track rail 51, the ball 58 sandwiched between the restraining portion 62 of the end plate 54 and the ball rolling groove 51 a of the track rail 51 is moved to the track rail 51. It is drawn into the loaded ball rolling path 57 between the ball rolling groove 51 a and the loaded ball rolling groove 53 a of the moving block main body 53. For this reason, the ball 58 can be smoothly circulated.

  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 motion guide device includes a ball spline. Moreover, a roller can be used for a rolling element instead of a ball. A spacer for preventing contact between the balls may be interposed between the balls.

  The Gothic arch groove shape may be composed of two spline curves, two clothoid curves, etc., as long as it is a curve that can contact the ball at two points, even though it is not composed of two arcs.

  The cross-sectional shape of the restricting portion of the circulation member is not limited to the Gothic arch groove shape, and may be formed into a circular arc groove shape formed of a single arc as long as play of the ball can be reduced. The shape of the restraint portion viewed from the axial direction of the screw shaft may not be linearly extended but may be bent in an arc shape corresponding to the ball rolling groove of the screw shaft.

  The ball screw circulation method is not limited to the return pipe method, but may be an end cap method.

The perspective view of the ball screw of a first embodiment of the present invention. Nut perspective view Enlarged view of circulation member Cross-sectional view of ball rolling groove on screw shaft and loaded ball rolling groove on nut Perspective view of nut with circulation member removed Perspective view showing circulation path of ball screw Diagram showing the center line of the circulation path as seen from the side of the nut Diagram showing the center line of the no-load return path as seen from the axial direction of the nut Perspective view of no-load return path developed on screw shaft Perspective view of screw shaft and circulation member Front view of screw shaft and circulating member Perspective view of circulating member attached to nut Front view of circulating member attached to nut (including partial cross section) The figure which shows the change of the cross-sectional shape of the no-load return path of a circulation member The figure which shows the change of the cross-sectional shape of the no-load return path of a circulation member Detailed view of cross section of curved passage Conceptual diagram showing chamfering of a conventional ball screw Front view of circulation path to achieve perfect integer winding Front view showing two balls arranged on top of screw shaft The perspective view of the ball screw of the second embodiment of the present invention. Nut side view Front view of nut Top view of nut Top view of the nut with the circulation member removed The perspective view of the division body of a circulation member Perspective view of circulation member Detailed view of the lifting part of the circulating member (IIXVI part in Fig. 26) Perspective view of circulation path Side view of circulation path The perspective view of the motion guide apparatus of 3rd embodiment Cross section of circulation path Detailed view of restraint part (IIIXI part enlarged view of FIG. 31) Conceptual diagram showing a ball moving on a conventional no-load return path

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a ... Ball rolling groove (rolling element rolling groove), 1 ... Screw shaft, 2 ... Nut, 2a ... Loaded ball rolling groove (loaded rolling element rolling groove), 3 ... Ball (rolling element), 8 ... Circulation 8a ... end part, 8b ... main body part, 10 ... unloaded return path, 12 ... loaded ball rolling path (loaded rolling element rolling path), 14 ... lifting section, 18 ... divided body, 22 ... curved path, 23 ... Radial passage, 24 ... Axial passage, 28 ... Restraint portion, 31 ... Screw shaft, 31a ... Ball rolling groove (rolling element rolling groove), 32 ... Nut, 32a ... Load ball rolling groove (load rolling element) Rolling groove), 34 ... circulating member, 35 ... unloaded return path, 36 ... curved path, 37 ... radial path, 38 ... axial path, 39 ... divided body, 40 ... raised portion, 41 ... ball (rolling) (Moving body), 42 ... restraining portion, 51 ... track rail (track member), 51a ... ball rolling groove (rolling body rolling portion) , 52 ... Moving block, 53 ... Moving block main body (moving member main body), 53a ... Loaded ball rolling groove (loaded rolling element rolling portion), 54 ... End plate (lid member), 55 ... Unloaded return path, 56 ... direction change path, 57 ... load ball rolling path (load rolling element rolling path), 58 ... ball (rolling element), 62 ... restraint part

Claims (4)

A screw shaft having a spiral rolling element rolling groove on the outer peripheral surface;
A nut having a spiral loaded rolling element rolling groove facing the rolling element rolling groove of the screw shaft on the inner peripheral surface;
A circulating member connected to one end and the other end of the loaded rolling element rolling groove of the nut, and having a cross-sectional unloaded return path surrounding the rolling element,
Circulation is possible in a circulation path constituted by 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 the no-load return path of the circulation member. A plurality of rolling elements arranged in a
The end of the circulation member in the lengthwise direction of the no-load return path is opposed to the rolling element rolling groove of the screw shaft and between the rolling element rolling groove of the screw shaft. A restraining part that sandwiches the moving body is provided,
By providing the restraining portion on the circulation member, an intermediate region is provided between the unloaded return path and the loaded rolling element rolling path,
By rotating the screw shaft relative to the nut, the rolling element sandwiched between the restraining portion of the circulation member and the rolling element rolling groove of the screw shaft is the load rolling element rolling path. Or drawn into the no-load return path ,
The rolling element is a ball;
The cross-sectional shape of the loaded rolling element rolling groove of the nut is formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball,
The cross-sectional shape of the restraining portion of the circulation member in a plane orthogonal to the traveling direction of the ball is formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball. Screw device. A screw shaft having a spiral rolling element rolling groove on the outer peripheral surface;
A nut having a spiral loaded rolling element rolling groove facing the rolling element rolling groove of the screw shaft on the inner peripheral surface;
A circulating member connected to one end and the other end of the loaded rolling element rolling groove of the nut, and having a cross-sectional unloaded return path surrounding the rolling element,
Circulation is possible in a circulation path constituted by 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 the no-load return path of the circulation member. A plurality of rolling elements arranged in a
The end of the circulation member in the lengthwise direction of the no-load return path is opposed to the rolling element rolling groove of the screw shaft and between the rolling element rolling groove of the screw shaft. A restraining part that sandwiches the moving body is provided,
By providing the restraining portion on the circulation member, an intermediate region is provided between the unloaded return path and the loaded rolling element rolling path,
The play of the rolling element between the rolling element rolling groove of the screw shaft and the restraining portion of the circulation member is smaller than or absent from the play of the rolling element in the unloaded return path ,
The rolling element is a ball;
The cross-sectional shape of the loaded rolling element rolling groove of the nut is formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball,
The cross-sectional shape of the restraining portion of the circulation member in a plane orthogonal to the traveling direction of the ball is formed in a Gothic arch groove shape including two arc-shaped curves having a radius of curvature larger than the radius of the ball. Screw device. The screw device according to claim 1 or 2 , wherein the restraining portion of the circulation member extends linearly so that play of the ball gradually decreases toward the load rolling element rolling path. The no-load return path of the circulation member is provided with a curved passage that is connected to the restraining portion and has a center line that is a convex arcuate curve toward the screw shaft when viewed from the axial direction of the nut. The screw device according to any one of claims 1 to 3 .

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