WO2010013706A1

WO2010013706A1 - Screw device

Info

Publication number: WO2010013706A1
Application number: PCT/JP2009/063416
Authority: WO
Inventors: 白井　武樹; 飯田　勝也; 荘志宮原; 勉富樫
Original assignee: Thk株式会社
Priority date: 2008-07-31
Filing date: 2009-07-28
Publication date: 2010-02-04
Also published as: JPWO2010013706A1; TW201013072A; JP5341893B2; TWI473948B

Abstract

A screw device enabling integer winding and also enabling rolling elements to circulate smoothly. The screw device comprises a screw shaft (1) having a spiral rolling element rolling groove (1a) in the outer peripheral surface, a nut (2) having a spiral load rolling element rolling groove (2a) facing the rolling element rolling groove (1a) of the screw shaft (1) in the inner peripheral surface and also having a no-load return passage (10) connected to one and the other ends of the load rolling element rolling groove (2a), and a plurality of rolling elements (3) so arranged as to be circulated through a circulation path comprising a load rolling element rolling passage between the rolling element rolling groove (1a) of the screw shaft (1) and the load rolling element rolling groove (2a) of the nut (2) and the no-load return passage (10). The no-load return passage (10) comprises a pick-up passage (22) the center line of which is arcuate when viewed from the axial direction of the nut (2) and which picks up the rolling elements (3) moving in the load rolling element rolling passage along the arcuate path and an axial passage (24) the center line of which is parallel to the axis of the nut (2) and which allows the rolling elements (3) to move parallel to the axis of the nut (2).

Description

Screw device

According to the present invention, a plurality of rolling elements are interposed between a spiral rolling element rolling groove on the outer peripheral surface of the screw shaft and a helical load rolling element rolling groove on the inner peripheral surface of the nut so as to allow rolling motion. It relates to a screw device.

The 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 in the loaded ball rolling path so as to allow rolling motion.

¡A return pipe is attached to the nut to circulate the ball rolling between the screw shaft and the nut. 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 screw shaft and the nut rolls up to one end of the loaded ball rolling groove of the nut, and then scoops up into the no-load return path of the return pipe. It is returned to the other end of the load ball rolling groove.

The one end and the other end of the load ball rolling groove of the nut are 180 degrees apart in the circumferential direction when viewed from the axial direction of the screw shaft. For this reason, the number of turns of the load ball rolling path is 2.5, 3.5, or the like. When the number of turns becomes such, the number of balls in the upper half of the nut where the return pipe is provided is different from the number of balls in the lower half of the nut where the return pipe is not provided, as viewed from the axial direction of the screw shaft. End up. Since the load that can be loaded is different between the upper half of the nut and the lower half of the nut, the load balance of the ball screw is deteriorated.

If the number of turns of the load ball rolling path can be made close to an integer such as 2, 3, 4, etc., this problem can be solved. Patent Document 1 discloses a ball screw in which the number of turns of a load ball rolling path is close to an integer.

In the ball screw described in Patent Document 1, the circulating component for circulating the ball is composed of a return tube extending in the axial direction of the nut and a pair of inserts attached to both ends of the return tube in the axial direction. . The nest lifts the ball moving on the load ball rolling path in the radial direction of the screw shaft and moves it to the return tube. The return tube is disposed parallel to the axis of the screw shaft. When viewed from the axial direction of the screw shaft, the position of the front nesting up the ball and the position of the back nesting up the ball coincide. For this reason, the number of turns of the load ball rolling path can be made an integer.

No. 6-37227

However, in the ball screw described in Patent Document 1, since the ball rolling on the outer peripheral surface of the screw shaft collides with the nest and suddenly changes its moving direction in the radial direction, it cannot be smoothly circulated. There's a problem. In addition, since the circulating component is composed of a return tube and a pair of inserts provided at both ends in the lengthwise direction of the return tube, there is a problem that the number of components increases. That is, although the ball screw described in Patent Document 1 can realize integer winding, it cannot be said to be a practical ball screw due to smooth circulation of the balls and problems in the production of circulating parts.

Therefore, an object of the present invention is to provide a highly practical screw device that can realize integer winding.

The present invention will be described below.
In order to solve the above-described problem, an aspect of the present invention is to provide a screw shaft having a spiral rolling element rolling groove on an outer peripheral surface and a spiral facing the rolling element rolling groove of the screw shaft on an inner peripheral surface. A loaded rolling element rolling groove, a nut having a no-load return path connected to one end and the other end of the loaded rolling element rolling groove, the rolling element rolling groove of the screw shaft, and the A load rolling element rolling path between the nut and the load rolling element rolling groove, and a plurality of rolling elements arranged to circulate in a circulation path composed of the no-load return path, and the no load The return path has a center line formed in an arc shape when viewed from the axial direction of the nut, and a hoisting passage that scoops up the rolling element that moves on the rolling element rolling path along the arc-shaped path, A line is formed parallel to the axis of the nut, and the rolling element is connected to the axis of the nut. The axial passage to move to the line, a screw device having a.

According to one aspect of the present invention, the rolling elements that move on the outer peripheral surface of the screw shaft can be scooped up along the arcuate track, so that the rolling elements can be smoothly circulated. In addition, by providing an axial passage parallel to the nut axis in the no-load return path and circulating the ball parallel to the nut axis, the inlet and outlet of the no-load return path seen from the nut axial direction are at the same position. The number of turns of the loaded rolling element rolling path can be made closer to an integer.

The perspective view of the ball screw of a first embodiment of the present invention. Nut perspective view Enlarged view of circulating parts Cross-sectional view of ball rolling groove on screw shaft and loaded ball rolling groove on nut Perspective view of nut with circulating parts 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 A perspective view of the unloaded return path developed on the screw shaft ((a) shows a perspective view, (b-1) shows a front view, and (b-2) shows a side view) Perspective view of screw shaft and circulating parts Front view of screw shaft and circulating parts Perspective view of circulating parts attached to nut Front view of the circulating parts attached to the nut (including a partial cross section) The figure which shows the change of the cross-sectional shape of the no-load return path of circulation parts The figure which shows the change of the cross-sectional shape of the no-load return path of circulation parts Detailed view of cross section of dredging 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 circulating parts removed Perspective view of divided parts of circulating parts Perspective view of circulating parts Detailed view of the lifting part of the circulating parts (IIXVI part in Fig. 26) Perspective view of circulation path Side view of circulation path The figure which shows the ball screw of 3rd embodiment of this invention ((a) in the figure shows sectional drawing along the axis line of a screw axis | shaft, (b) shows a front view) The perspective view which shows the end piece attached to the end surface of a nut Sectional view showing the ball moving the end piece A perspective view of a ball screw according to a fourth embodiment of the present invention. Cross section of bearing The figure which shows an example of the usage method of the ball screw of 4th embodiment of this invention. The figure which shows the circulation path of the ball screw of 4th embodiment of this invention ((a) shows a front view, (b) shows a side view in the figure) The graph which shows the relationship between the position of a ball | bowl, and a ball | bowl load ((a) in the figure is an example of the present invention, (b) is a conventional example using a return pipe)

FIG. 1 shows a perspective view of a ball screw as a screw device of a first embodiment of the present invention. The ball screw has a screw shaft 1 having a ball rolling groove 1a which is a spiral rolling element rolling groove on the outer peripheral surface, and a spiral load rolling element rolling groove facing the ball rolling groove 1a on the inner peripheral surface. A load ball rolling groove 2a and a nut 2 having a no-load return path connecting one end and the other end of the load ball rolling groove 1a, and a ball rolling groove 1a of the screw shaft 1 and a load ball of the nut 2 And a ball 3 (see FIG. 4) that is a plurality of rolling elements interposed in a circulation path composed of a loaded ball rolling path and an unloaded return path between the rolling grooves 2a.

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. A contact angle θ formed by a line connecting the center C2 of the ball 3 and the bottom 5 of the gothic arch groove and a 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.

2 and 3 are perspective views of the nut 2 with the screw shaft 1 removed. The nut 2 is composed of a nut main body 9 in which a spiral load ball rolling groove 2 a is formed on the inner peripheral surface, and a circulating component 8 attached to the nut main body 9. The nut body 9 is provided with a through hole 2e through which the screw shaft 1 passes. On the inner peripheral surface of the nut body 9, a spiral load 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.

At one end of the nut body 9 in the axial direction, a flange 2b for attaching the nut body 9 to the other machine part is formed. A flat chamfered portion 2 c is formed on the outer peripheral surface of the nut body 9. A circulating component 8 is mounted on the flattening portion 2c. The circulation part 8 is formed with a no-load return path 10 (see FIG. 6) connected to one end and the other end of the load ball rolling groove of the nut body 9.

FIG. 5 shows a perspective view of the circulating component 8 and the nut body 9. The unloaded return path 10 of the circulating component 8 has a 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 body 9 at both ends in the length direction. A pair of hoisting passages 22 for hoisting the rolling ball 3 into the no-load return path 10 is provided. Each lifting path 22 is formed with a lifting part 14 that contacts the ball 3 moving on the loaded ball rolling path and guides it into the no-load return path 10. A pair of through holes 15 that penetrate from the outer surface to the inner surface of the nut body 9 and into which the pair of raised portions 14 of the circulating component 8 are fitted are formed in the flattening portion 2 c of the nut body 9. The through hole 15 extends along the load ball rolling groove 2 a of the nut body 9. A notch groove 16 extending in the axial direction of the nut body 9 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 16a is parallel to the plane of the chamfered portion 2c and parallel to the axis of the nut body 9. The inner wall surface 16b is parallel to the axis of the nut body 9 and is orthogonal to a plane including the groove bottom 16a.

The circulating component 8 is fitted into the through hole 15 and the notch groove 16 of the nut body 9. The external shape of the circulating component 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 8a extends elongated along the load ball rolling groove 2a of the nut body 9. 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 main body 9. 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 circulating component 8 is formed by combining a pair of divided bodies 18 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. By configuring the circulating component 8 from a pair of divided bodies 18 divided into two along the no-load return path 10, the number of components can be reduced.

As shown in FIG. 2, when the circulating component 8 is attached to the nut body 9, the pair of end portions 8 a of the circulating component 8 fit into the pair of through holes 15 of the nut body 9. And the main-body part 8b of the circulation component 8 fits into the notch groove 16 of the nut main body 9. FIG. As shown in FIG. 3, the upper portion 20 of the main body portion 8 b of the circulating component 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 body 9 by passing a bolt through the through hole 21 c and screwing the bolt into the screw hole of the nut body 9. The circulating component 8 is sandwiched between the pressing member 21 and the notch groove 16 of the nut body 9 and is fixed to the nut body 9.

As shown in FIG. 5, the circulating component 8 fits into the notch groove 16 of the nut body 9, and the bottom surface 19 of the body portion 8 b of the circulating component 8 contacts the groove bottom 16 a of the notch groove 16 of the nut body 9. Thus, the position of the circulating component 8 in the X direction is positioned on a plane orthogonal to the axis of the nut body 9. Further, when the outer wall surface of the main body portion 8 b of the circulating component 8 comes into contact with the inner wall surface 16 b of the notch groove 16 of the nut body 9, the position of the circulating component 8 on the plane is positioned in the Y direction. Then, when the end 8 a of the circulating component 8 is fitted into the through hole 15 of the nut body 9, the Z-direction position of the circulating component 8 in the axial direction of the nut body 9 is positioned. That is, when the circulating component 8 is fitted into the nut body 9, the circulating component 8 is accurately positioned with respect to the nut body 9, and consequently the raised portion 14 of the circulating component 8 is accurately positioned with respect to the load ball rolling groove 2 a of the nut body 9. Can be positioned. Thereby, the ball 3 can be smoothly moved between the no-load return path 10 and the loaded ball rolling path 12. Further, by sandwiching the circulating component 8 between the inner wall surfaces 16b of the notch groove 16, it is possible to prevent the divided surface 24a of the circulating component 8 divided into two 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 body 9. A no-load return path 10 is connected to one end and the other end of the load ball rolling path 12 so that the ball 3 moving from one end to the other end of the load 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 circulating component 8. The no-load return path 10 has an axial passage 24 parallel to the axis of the nut 2 so that the number of turns of the load ball rolling path 12 is close to an integer such as 2, 3, 4, and so on. At both ends of the axial passage 24, a connecting passage 23 and a lifting passage 22 are formed.

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 a pair of lifting paths 22, a pair of connecting paths 23, and an axial path 24. As shown in FIG. 8, the hoisting passage 22 has a center line formed in an arc shape when viewed from the axial direction of the nut 2, and moves the ball 3 moving on the load ball rolling path 12 along the arc-shaped track. Crawling up. Here, the arc shape includes an arc, an ellipse, and a clothoid curve. In the conventional ball screw, as viewed from the axial direction of the nut 2, the ball 3 is scooped up along a straight track in the tangential direction of the circular load ball rolling path 12. On the other hand, in the ball screw of the present embodiment, the ball 3 is scooped up along an arcuate path. A connection point P1 between the center line of the load ball rolling path 12 and the center line of the lifting path 22 as viewed from the axial direction of the nut 2 so that the ball 3 moves smoothly from the loaded ball rolling path 12 to the lifting path 22. The tangent directions of these center lines coincide with each other at (lifting point).

As shown in FIG. 7, when viewed from the side of the nut 2, the center line of the lifting passage 22 is orthogonal to the axis 2 f of the nut 2. The center line of the connecting passage 23 connecting the lifting passage 22 and the axial passage 24 is formed in an arc shape. The connecting passage 23 moves the ball 3 in the radial direction and moves the ball 3 inward of the nut 2. The connecting passage 23 is bent at 90 degrees in the axial direction, and then connected to the axial passage 24 whose center line is 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 connecting path 23 and the lifting path 22 on the opposite side. As shown in FIG. 8, the front side lifting path 22 and the rear side lifting path 22 are formed symmetrically with respect to the center line 2 g of the nut 2. Note that the center line of the lifting passage 22 viewed from the side of the nut 2 may be inclined in accordance with the lead of the load ball rolling path 12. By tilting in accordance with the lead, the ball can be moved more smoothly.

FIG. 9A shows a perspective view of the no-load return path 10 developed on the screw shaft 1. An unloaded return path 10 viewed from the axial direction of the nut 2 by providing an axial path 24 parallel to the axis of the nut 2 in the unloaded return path 10 of the circulating component 8 and circulating the ball 3 in parallel with the axis 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 lifting path 22 of the circulating component 8 scoops up the ball 3 along the arc-shaped track, the ball 3 can be smoothly circulated and the number of turns of the load ball rolling path 12 can be made closer to an integer. it can.

As shown in FIG. 9 (b-1), the hoisting passage 22 of the no-load return passage 10 has a center line formed in an arc shape when viewed from the axial direction of the nut 2, and FIG. 9 (b-2). ), The center line of the nut 2 has a non-linear region 22a formed in an arc shape as viewed from the side. When the lifting passage 22 formed in an arc shape when viewed from the axial direction of the nut 2 and the connecting passage 23 formed in an arc shape when viewed from the side of the nut 2 are connected via a straight region, the radial direction of the nut 2 The dimensions of will become larger. The radial dimension of the nut 2 can be reduced by forming an arc-shaped non-linear region in the lifting passage 22 when viewed from the axial direction of the nut 2 or from the side of the nut 2. A part of the hoisting passage 22 may be a non-linear region 22a, or the entire hoisting passage 22 may be a non-linear region 22a.

10 and 11 show the screw shaft 1 and the circulating component 8. A no-load return path 10 developed on the screw shaft 1 is formed in the circulating component 8. The no-load return path 10 of the circulating component 8 is formed in a circular shape surrounding the ball 3. The unloaded return path 10 of the circulating component 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 circulating component 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 connecting passage 23 and the lifting passage 22 are divided into two at 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 lifting passage 22.

12 and 13 are detailed views of the circulating component 8 attached to the nut body 9. In the lifting passage 22 of the circulating component 8, a lifting portion 14 is formed for scooping up the ball 3 rolling on the loaded ball rolling path 12. 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 connecting passage 23. An arcuate curved surface is formed on the inner peripheral surface 14 b of the lifting portion 14. The raising portion 14 gradually increases in thickness as it approaches the screw shaft 1. By increasing the thickness of the lower end of the hoisting portion 14, the strength of the hoisting portion 14 with which the ball 3 collides can be increased.

As shown in FIG. 13, a constraining portion 28 that faces the ball rolling groove 1 a of the screw shaft 1 is formed at the end of the hoisting passage 22 of the circulating component 8. The restraining portion 28 is connected to the load ball rolling groove 2 a of the nut body 9. 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 body 9. 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 circulating component 8 is smaller than the play of the ball 3 in the unloaded return path 10 having a closed curved cross section. By providing the restraining portion 28, the trajectory of the ball 3 that moves between the no-load return path 10 and the loaded ball rolling path 12 can be stabilized.

The cross-sectional shape of the raised portion 14 of the circulating component 8 in a plane orthogonal to the traveling direction of the ball 3 is formed into a circular arc groove shape composed 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 connecting passage 23 and the axial passage 24 of the circulation component 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 circulating component 8. In the region from (1) to (2), that is, in the region of the load ball rolling path 12 and the restraint portion 28 of the circulating component 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 hoisting passage 22, the cross-sectional shape of the outer side of the hoisting passage 22 is gradually changed from a Gothic arch groove shape matched to the restraining portion 28 to a circular arc groove shape. To change. The cross-sectional shape of the hoisting portion 14 inside the hoisting passage 22 is formed in a circular arc groove shape. In the region from (3) to (4), that is, in the region of the connecting 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 lifting passage 22 that is an area from (2) to (3). In the hoisting passage 22, the cross-sectional shape on the nut body 9 side (restraint portion 28 side) is formed in a Gothic arch groove shape composed of two arcs R <b> 1. 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 load ball rolling path 12, the ball 3 is sandwiched between the ball rolling groove 1 a of the screw shaft 1 and the load ball rolling groove 2 a of the nut body 9, and compressive load is applied. Roll while exercising. On the other hand, in the no-load return path 10 of the circulating component 8, there is a slight play between the ball 3 and the no-load return path 10, and the ball 3 moves while being pushed by the subsequent ball 3 without being loaded. To do.

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 area and a load ball rolling path 12 in the load area. On the other hand, in the ball screw of this embodiment, a restraint portion 28 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 there is an intermediate area with little play. Exists. 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 no-load return path 10, the ball 3 is guided between the restraining portion 28 of the circulating component 8 and the screw shaft 1. Can be moved smoothly inward.

Further, by forming the cross-sectional shape of the restraining portion 28 of the unloaded return path 10 of the circulating component 8 into a Gothic arch groove shape that matches the cross-sectional shape of the loaded ball rolling groove 2 a of the nut body 9, the restraining portion 28 correctly The aligned balls 3 can be smoothly moved to the loaded ball rolling groove 2a. By making the play of the ball 3 in the restraining portion 28 gradually become smaller as it approaches 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 no-load return path 10 of the circulating component 8 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 body 9 is formed in a Gothic arch groove shape. For this reason, it was necessary to process the chamfer 29 for making the cross-sectional shape continuous at the joint of the load ball rolling groove 2a of the nut body 9. On the other hand, by forming the cross-sectional shape of the restraining portion 28 of the circulating component 8 in a Gothic arch groove shape as in the present embodiment, the ball 3 can be removed from the no-load return path 10 without chamfering the nut. It is possible to easily transfer to the loaded ball rolling groove 2a.

As shown in FIG. 13, the ball 3 collides with the lifting unit 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 hoisting portion 14 into a circular arc groove shape and rounding the tip of the hoisting portion 14 into an arc shape, it is possible to prevent an edge from occurring at the tip of the hoisting portion 14. In addition, by forming the cross-sectional shapes of the connecting 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 complete integer winding. When viewed from the axial direction of the nut 2, the center S1 of the screw shaft 1 is derived from a line L1 (center line) connecting the center S1 of the screw shaft 1 and the center of the axial passage 24 of the circulating component 8 (center line of the connecting passage 23). Of the ball 3 in the load ball rolling path 12 up to a line L2 connecting the boundary B1 (see FIG. 13, the circulation start point) between the load ball rolling groove of the nut body 9 and the lifting path 22 of the circulating component 8. The distance α on the center arc-shaped orbit is set to be larger than 0 and 1.5 times or less of the ball diameter. The shorter the distance α is, the more difficult it is to turn, so that the center line of the lifting passage 22 exceeds the center line L1 of the nut 2 and then returns to the center line L1 of the nut 2 again. 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 arc-shaped distance α is equal to or greater than 1 · Da (diameter), the number of balls 3 that can receive a load is reduced by one at the position where the balls 3 are scooped up, compared to 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 shows a perspective view of the 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 ball rolling groove 31a is formed on the screw shaft 31, and the load ball rolling groove 32a is formed on the nut body 44, which is the same as the ball screw of the first embodiment.

21 and 22 show the nut 32 to which the circulating component 34 is attached. The circulation part 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 lifting path 36 (see FIG. 22) for scooping up the ball moving on the loaded ball rolling path 33 along an arcuate path, and a connecting path 37 for moving 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.

23, the circulating component 34 is formed by combining a pair of divided bodies 39 that are divided into two along the axis of the nut 32.

24, the nut main body 44 is formed with a pair of through holes 32b penetrating from the outside to the inside. The pair of through holes 32 b are arranged in the axial direction of the nut body 44.

25 and 26 show detailed views of the circulating component 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 portion in the length direction of the no-load return path 35 of the circulating component 34 that is connected to the load ball rolling groove 32a of the nut body 44. A ball 41 is sandwiched between the restraining portion 42 and the screw shaft 31. The cross-sectional shape of the restraining 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 body 44. On the other hand, the cross-sectional shape of the raised portion 40 of the circulating component 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 body 44. 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 circulating component 34. The balls 41 that have passed through the lifting passage 36, the connecting passage 37, and the axial passage 38 of the circulating component 34 are returned to the loaded ball rolling passage 33 again via the opposite connecting passage 37 and the lifting passage 36. When the ball 41 is returned to the load ball rolling path 33, the rotation of the screw shaft 31 causes the ball 41 sandwiched between the screw shaft 31 and the restraining portion 42 of the circulating component 34 to be drawn into the load ball rolling path 12. For this reason, the ball 41 can be moved smoothly.

FIG. 30 shows a ball screw according to a third embodiment of the present invention. In the figure, (a) shows a sectional view of the ball screw, and (b) shows a front view. Unlike the first and second embodiments, the structure of the circulating component for circulating the balls is different from that of the first and second embodiments, and an end piece 54 as a circulating component is attached to the end surface 53 a of the nut body 53 in the axial direction.

A spiral ball rolling groove 51 a is formed on the outer peripheral surface of the screw shaft 51. In this embodiment, the number of the ball rolling grooves 51a is two. On the inner peripheral surface of the nut main body 53 of the nut 52, a spiral load ball rolling groove 52a facing the ball rolling groove 51a of the screw shaft 51 is formed. A spiral load ball rolling path 55 is formed between the ball rolling groove 51 a of the screw shaft 51 and the load ball rolling groove 52 a of the nut body 53. A through hole 56 is provided in the nut main body 53 in parallel with its axis. The through hole 56 constitutes an axial passage of the no-load return path. As in this embodiment, the nut through-hole 56 itself may constitute an axial passage, or a pipe inserted into the through-hole 56 may constitute an axial passage.

As shown in FIG. 31, a recess 53b is formed in the end surface 53a of the nut main body 53, and an end surface piece 54 as a circulating part is fitted into the recess 53b. The recess 53 b communicates with the through hole 56, and a pair of end face pieces 54 are provided at both ends in the length direction of the through hole 56. The end face piece 54 is formed with a lifting passage and a connecting passage. The configurations of the hoisting passage and the connecting passage are the same as those of the ball screw of the first embodiment. The end face piece 54 is provided with a screw hole 54a. The end face piece 54 is fixed to the nut body 53 by passing a screw through the screw hole 54 a and tightening the screw to the nut body 53. The end face piece 54 may be divided into two along the hoisting passage and the connecting passage, or may not be divided into two.

FIG. 32 shows the trajectory of the ball 59 moving in the lifting path 58 of the end face piece 54. The ball 59 moving on the load ball rolling path 55 is lifted up by the lifting portion 61 of the lifting path 58. The center line of the lifting path 58 is formed in an arc shape that is continuous with the center line of the load ball rolling path 55. The ball 59 is scooped up along an arcuate track. Also in this ball screw, like the ball screw of the first and second embodiments, the hoisting along the arcuate track contacting the loaded ball rolling path 55, the increase in the number of effective balls, and the strength of the hoisting portion are increased. Improvement and load balance can be improved.

FIG. 33 shows a ball screw according to a fourth embodiment of the present invention. In the ball screw of this embodiment, a bearing 74 is integrally provided on the outer periphery of the nut body 73. 34, the bearing 74 includes an inner ring 75 integral with the nut body 73, an outer ring 76 disposed outside the inner ring 75, and between the inner ring 75 and the outer ring 76. A plurality of rolling element rows arranged, for example, two roller rows are arranged.

On the outer peripheral surface of the inner ring 75, two rows of roller rolling surfaces 75a having a V-shaped cross section are formed. The outer ring 76 is processed with a plurality of counterbores 76b for attaching the outer ring 76 to a counterpart component like a flange. On the inner peripheral surface of the outer ring 76, two rows of roller rolling surfaces 76a having a V-shaped cross section facing the roller rolling surface 75a of the inner ring 75 are formed. Between the roller rolling surface 75a of the inner ring 75 and the roller rolling surface 76a of the outer ring 76, two rows of annular roller rolling paths having a square cross section are formed. A plurality of rollers 77 are arranged on the roller rolling path. The roller 77 has a substantially quadrangular side surface, and its diameter is slightly larger than the axial length. In each roller rolling path, a plurality of rollers 77 are arranged in a cross so that the axes of the adjacent rollers 77 are orthogonal to each other when viewed from the direction of travel of the rollers 77. By arranging the rollers 77 in a cross arrangement, the bearing 74 becomes an angular contact bearing capable of applying a load in the axial direction of the nut 72 (a load in the directions (1) and (2) in the drawing) and a radial load. A plurality of rollers 77 are arranged in parallel so that only the load in the direction (1) in the figure can be applied to the roller rolling path in one row, and only the load in the direction (2) in the figure is placed on the roller rolling path in the other row. A plurality of rollers 77 may be arranged in parallel so that the load can be applied. The contact angle line of the roller rolling path in one row at this time is indicated by (3) in the figure, and the contact angle line of the roller in the other row is indicated by (4) in the figure. The parallel arrangement means that the axes of adjacent rollers are arranged in a substantially parallel state. When the rollers are arranged in a cross arrangement, the number of rows of rollers may be one.

33, a spiral ball rolling groove 71a is formed on the outer peripheral surface of the screw shaft 71. As shown in FIG. In this embodiment, two ball rolling grooves 71a are formed. A load ball rolling groove facing the ball rolling groove 71 a of the screw shaft 71 is formed on the inner peripheral surface of the nut body 73. A spiral loaded ball rolling path is formed between the ball rolling groove 71 a of the screw shaft 71 and the loaded ball rolling groove of the nut body 73. An axial passage parallel to the axis of the nut body 73 is formed inside the nut body 73. A pair of side piece 80 as a circulating part is attached to both ends of the nut body 73 in the lengthwise direction of the axial passage. Each side piece 80 is formed with a lifting passage and a connecting passage. The hoisting passage has a center line formed in an arc shape when viewed from the axial direction of the nut. The connecting passage has a center line formed in an arc shape when viewed from the side of the nut, and connects the lifting passage and the axial passage. The side piece 80 is fitted into a recess provided in the outer diameter portion of the nut body 73. A circulation path is constituted by the load ball rolling path, the lifting path, the axial path, and the connecting path. The number and arrangement of circulation paths will be described later.

FIG. 35 shows an example of how to use the ball screw with bearing of the fourth embodiment. A table 82 is coupled to both ends of the screw shaft 71 via a support portion 81. The outer ring 76 of the bearing 74 is fixed to a base (not shown). When the nut main body 73 is rotated with respect to the outer ring 76 of the bearing 74 by the motor, the screw shaft 71 moves in the axial direction, and the table 82 moves. In order to accurately position the moving table 82, the bearing 74 needs not only a mechanism for guiding rotation but also high rigidity. By using an angular contact bearing using the roller 77, the rigidity of the bearing 74 can be increased.

As a method of using the ball screw, it is common to fix the table to the nut and rotate the screw shaft whose both ends are rotatably supported by the base to move the nut in the axial direction of the screw shaft. The ball screw of the first to third embodiments is used in a general usage method.

FIG. 36 shows a ball screw circulation path 84 of the fourth embodiment. In this embodiment, two rows of circulation paths 84 are provided with their positions shifted in the axial direction of the screw shaft. In addition, two circulation paths 84 are provided corresponding to the two screw shafts 71. The total number of circulation paths 84 is represented by the product of the number of columns and the number of strips. In this embodiment, a total of four circulation paths are provided by two rows × two strips. The four no-load return paths 85 of the circulation paths are arranged at equal intervals of 90 degrees in the circumferential direction when viewed from the axial direction of the screw shaft 71, as shown in FIG. Further, the distance β between the first row of loaded ball rolling grooves and the second row of loaded ball rolling grooves is adjusted so that a preload can be applied to the ball screw. The phase of the loaded ball rolling groove in the first row and the loaded ball rolling groove in the second row are slightly shifted from the ball rolling groove 71 a of the screw shaft 71.

According to the ball screw of this embodiment, the number of turns of the loaded ball rolling path is made close to an integer, and the number of balls that cannot receive the load is reduced, so that the ball load of the balls in the nut can be made uniform. This will be described below. FIG. 37B shows the ball load distribution of a conventional return pipe type ball. When the return pipe 87 indicated by the broken line in FIG. 36A is attached, there are many portions 89 where there is no ball that receives the load in the axial direction of the screw shaft 71. For this reason, as shown in the graph of FIG. 37 (b), a phenomenon occurs in which the ball load in the circulation path increases or decreases depending on the position of the ball. This is because the ball load increases when the number of balls receiving the load in the axial direction of the screw shaft 71 is small, that is, when the ball is positioned above the load ball rolling path 90 in FIG. On the other hand, when the number of balls receiving a load in the axial direction of the screw shaft 71 is large, that is, when the balls are positioned below the loaded ball rolling path 90 in FIG. On the other hand, the ball load of the balls in the nut can be made uniform as shown in FIG. The horizontal axis of the graph represents the position of the ball in the loaded ball rolling path 90.

Further, according to the ball screw of this embodiment, the averaging effect can be improved by increasing the length of the nut 72 in the axial direction and providing the nut 72 with a plurality of rows of circulation paths 84. Swaying can be reduced.

Furthermore, according to the ball screw of the present embodiment, the four unloaded return paths 85 are arranged at equal intervals in the circumferential direction of the nut 72, so that the balls are changed from the loaded ball rolling path 90 to the unloaded return path 85. The influence at the time of going in and out can be reduced, and the fluctuation of torque when the nut 72 is rotated can be reduced. By applying preload to the ball screw, torque fluctuation can be further reduced.

Furthermore, according to the ball screw of this embodiment, the rigidity in the axial direction of the ball screw can be improved by using a relatively small diameter ball and making it a double thread screw.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, a roller can be used for the rolling element instead of a ball.

The center line of the lifting path, the connecting path, and the axial path of the no-load return path may not be composed of a plurality of arcs and straight lines, but may be composed of a plurality of clothoid curves with continuous tangential directions.

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 constraining portion of the circulation part is not limited to the Gothic arch groove shape, and may be formed into a circular arc groove shape made of a single arc as long as play of the ball can be reduced.

If a complete integer winding is not required, the distance α on the circular orbit may be set to a value other than 0.4 times to 0.6 times the diameter Da.

DESCRIPTION OF

SYMBOLS

1, 31, 51, 71 ... Screw shaft, 1a, 31a, 51a, 71a ... Ball rolling groove (rolling body rolling groove), 2, 32, 52, 72 ... Nut, 9, 44, 53, 73 ... Nut Main body, 2a, 32a, 52a ... loaded ball rolling groove (loaded rolling element rolling groove), 3, 41, 59 ... ball (rolling element), 8, 34 ... circulating parts, 10, 35 ... unloaded return path, 12, 55 ... Loaded ball rolling path (loaded rolling element rolling path), 14, 40 ... Lifting section, 18, 39 ... Divided body, 22, 36, 58 ... Lifting path, 23, 37 ... Connecting path, 24, 38 ... Axial passage, 31 ... Screw shaft, 31a ... Ball rolling groove (rolling element rolling groove), 54 ... End face piece (circulation part), 74 ... Bearing, 75 ... Inner ring, 75a ... Roller rolling surface, 76 ... outer ring, 76a ... roller rolling surface, 77 ... roller, 84 ... circulation path

Claims

A screw shaft having a spiral rolling element rolling groove on the outer peripheral surface;
An unloaded return having a spiral loaded rolling element rolling groove facing the rolling element rolling groove of the screw shaft on the inner peripheral surface and connected to one end and the other end of the loaded rolling element rolling groove A nut having a path;
It is arranged to be able to circulate in a circulation path composed of 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. A plurality of rolling elements,
The no-load return path is
A hoisting passage that has a center line formed in an arc shape when viewed from the axial direction of the nut, and scoops up the rolling element that moves on the load rolling element rolling path along an arc-shaped track,
A screw device comprising: an axial passage having a center line formed parallel to the axis of the nut and moving the rolling element parallel to the axis of the nut.
The hoisting passage has a non-linear region in which a center line is formed in an arc shape when viewed from the axial direction of the nut and a center line is formed in an arc shape when viewed from the side surface direction of the nut. The screw device according to claim 1.
The nut is
A nut body in which the load rolling element rolling groove is formed on the inner peripheral surface;
A circulating part mounted on the nut body and forming the no-load return path;
3. The screw device according to claim 1, wherein the circulating component is formed by combining a pair of divided bodies that are divided into two along the no-load return path.
The nut is
A nut body in which the load rolling element rolling groove is formed on an inner peripheral surface and the axial passage is formed;
The screw device according to claim 1, further comprising: a circulating component that is mounted on an end surface or an outer diameter portion of the nut body in the axial direction and in which the hoisting passage is formed.
The rolling element is a ball;
The load rolling element rolling path from the line connecting the center of the screw shaft and the center of the axial path to the boundary between the lifting path and the load rolling element rolling path as seen from the axial direction of the nut 5. The screw device according to claim 1, wherein a distance on the track of the center of the ball is set to be greater than 0 and not more than 1.5 times the diameter of the ball.
When viewed from the axial direction of the screw shaft, at the connection point between the center line of the lifting passage and the center line of the load rolling element rolling path, the tangential direction of the center line of the lifting path and the load rolling element rolling path 6. The screw device according to claim 1, wherein a tangential direction of the center line substantially coincides with the center line.
The nut is
A nut body in which the load rolling element rolling groove is formed on the inner peripheral surface;
An inner ring provided integrally with the nut body and having a rolling element rolling surface on the outer peripheral surface;
An outer ring disposed on the outer peripheral side of the inner ring and having a rolling element rolling surface on the inner peripheral surface;
A plurality of rollers arranged so as to be able to roll between the rolling element rolling surface of the inner ring and the rolling element rolling surface of the outer ring,
The bearing comprising the inner ring, the outer ring, and the plurality of rollers is an angular contact bearing capable of being loaded with an axial load and a radial load of the nut. The screw device according to the above.
Two or more rows of circulation paths are provided by shifting the position in the axial direction of the screw shaft, and two or more cycles of circulation paths are provided corresponding to the number of two or more of the screw shafts,
The total number of circulation paths is represented by the product of the number of columns and the number of lines,
The unloaded return paths of the total number of circulation paths are arranged evenly in the circumferential direction of the screw shaft as viewed from the axial direction of the screw shaft. Screw device.