Motion guiding device

Abstract

The present invention provides a motion guiding device that can prevent a ball from contacting an edge of a ball rolling groove of a track member when the ball transfers from a rolling surface of an inner peripheral side (inner peripheral side member) of a direction conversion path to the track member. The motion guiding device includes: a track member (2) having a ball rolling groove (2a); and a moving member that is assembled to the track member (2) so as to be relatively movable. The moving member includes: a moving member main body having a load ball rolling groove opposed to the ball rolling groove (2a) and a return path substantially parallel to the load ball rolling groove; and a cover member having a direction conversion path. When observing a cross section of the motion guiding device orthogonal to the longitudinal direction of the track member (2), when the radius of curvature of the ball rolling groove (2a) is set to R and the distance from the ball center (O) to the rolling surface (21) of the inner peripheral side (inner peripheral side member (9a)) of the direction conversion path is set to r, it is set that R > r.

Description

Technical Field

[0001] The present invention relates to a motion guiding device for guiding the motion of a movable body such as a workbench. Background Art

[0002] There is known a motion guiding device (for example, refer to Patent Document 1) for guiding the motion (linear motion or curvilinear motion) of a movable body such as a workbench. The motion guiding device includes a rail member and a moving member that is assembled to the rail member so as to be relatively movable. A movable body such as a workbench is mounted on the moving member. A plurality of balls are interposed between the rail member and the moving member so as to be capable of rolling motion. By guiding the motion of the movable body by the rolling motion of the balls, the movable body can be guided with high precision and high rigidity.

[0003] A ball rolling groove is formed in the rail member. The moving member includes a moving member main body and a cover member. A load ball rolling groove opposed to the ball rolling groove and a return path substantially parallel to the load ball rolling groove are formed in the moving member main body. A direction conversion path connecting the load path and the return path between the ball rolling groove and the load ball rolling groove is formed in the cover member. The cover member includes a cover main body forming the outer peripheral side of the direction conversion path and an inner peripheral side member forming the inner peripheral side of the direction conversion path. A circulation path is constituted by the load path, the return path, and the direction conversion path. A plurality of balls are arranged in the circulation path. When the moving body relatively moves with respect to the rail member, the plurality of balls circulate in the circulation path.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-68880 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] However, in the conventional motion guiding device, when the ball transfers from the rolling surface of the inner peripheral side (inner peripheral side member) of the direction conversion path to the rail member, the ball contacts the edge of the ball rolling groove of the rail member. Therefore, although it generally does not cause a problem, if the motion guiding device is used in a high-speed region, high stress may be generated at the contact portion between the ball and the edge of the ball rolling groove, and indentations may be generated at the contact portion.

[0009] The present invention has been made in view of the above problems, and an object thereof is to provide a motion guiding device capable of preventing the ball from contacting the edge of the ball rolling groove of the rail member when the ball transfers from the rolling surface of the inner peripheral side of the direction conversion path to the rail member.

[0010] Means for Solving the Problems

[0011] In order to solve the above problems, one aspect of the present invention is a motion guiding device, which includes: a rail member having a ball rolling groove; and a moving member that is relatively movably assembled to the rail member. The moving member includes: a moving member main body having a load ball rolling groove opposed to the ball rolling groove and a return path substantially parallel to the load ball rolling groove; and a cover member having a direction conversion path connecting a load path between the ball rolling groove and the load ball rolling groove and the return path. A plurality of balls are arranged in a circulation path composed of the load path, the return path, and the direction conversion path. The motion guiding device is characterized in that, in a cross-sectional view of the motion guiding device orthogonal to the length direction of the rail member, when the radius of curvature of the ball rolling groove is set to R and the distance from the center of the ball to the rolling surface on the inner peripheral side of the direction conversion path is set to r, it is set that R > r.

[0012] Advantages of the Invention

[0013] According to the present invention, since the rolling surface is arranged inside the extension line of the ball rolling groove, it is possible to prevent the ball from contacting the edge of the ball rolling groove of the rail member when the ball transfers from the rolling surface to the rail member. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is an external perspective view (including a partial cross-sectional view) of a motion guiding device according to an embodiment of the present invention.

[0015] Figure 2 is a cross-sectional view of the circulation path of the motion guiding device of this embodiment.

[0016] Figure 3 is a perspective view of the cover member of the motion guiding device of this embodiment ( Figure 3 (a) is a perspective view of the cover member, Figure 3 and (b) is Figure 3 an enlarged view of part b of (a).

[0017] Figure 4 is a perspective view of the cover member of the motion guiding device of this embodiment ( Figure 3 with the viewing direction changed compared to

[0018] Figure 5 is a perspective view of the inner peripheral side member of the motion guiding device of this embodiment.

[0019] Figure 6 is a view showing the contact angle line of the motion guiding device of this embodiment.

[0020] Figure 7 is a cross-sectional view of the motion guiding device of this embodiment orthogonal to the length direction of the guide rail.

[0021] Figure 8 is a cross-sectional view orthogonal to the longitudinal direction of the guide rail of the motion guiding device ( Figure 8 (a) of which shows the present embodiment, Figure 8 (b) of which shows the prior art).

[0022] Figure 9 is a cross-sectional view orthogonal to the longitudinal direction of the guide rail of the motion guiding device of the present embodiment. Detailed Embodiment

[0023] Hereinafter, the motion guiding device of the embodiment of the present invention will be described based on the drawings. Among them, the motion guiding device of the present invention can be embodied in various ways and is not limited to the embodiment described in this specification. This embodiment is provided for the purpose of enabling those skilled in the art to fully understand the scope of the invention by making the disclosure of the specification sufficient.

[0024] Figure 1 Fig. shows an external perspective view (including a partial cross-sectional view) of a motion guiding device 1 according to an embodiment of the present invention. It should be noted that hereinafter, for the convenience of description, the motion guiding device 1 is arranged on a horizontal plane, and the directions of up and down, left and right, and front and back when observing the motion guiding device 1 from the front view, that is, Figure 1 will be used to describe the structure of the motion guiding device 1. Of course, the arrangement of the motion guiding device 1 is not limited to this.

[0025] As Figure 1 shown, the motion guiding device 1 includes a guide rail 2 as a track member and a block 3 as a moving member that can be assembled to move relative to the guide rail 2. The movement of the block 3 relative to the guide rail 2 is relative, and it can be the block 3 that moves or the guide rail 2 that moves.

[0026] The guide rail 2 extends linearly. Through holes 2b for bolts for mounting the guide rail 2 to the base are formed on the upper surface of the guide rail 2. Four ball rolling grooves 2a extending in the longitudinal direction of the guide rail 2 are formed on the left and right of the guide rail 2. In the present embodiment, a pair of protruding portions 20 protruding in the left and right directions are formed on the upper part of the guide rail 2, and two ball rolling grooves 2a are formed above and below each protruding portion 20. The cross-sectional shape of the ball rolling groove 2a is a single arc or a cusp. It should be noted that the guide rail 2 may also extend in a curved shape. The number and arrangement of the ball rolling grooves 2a can be appropriately changed according to the use of the motion guiding device 1.

[0027] The block 3 is in an inverted U shape when viewed from the front, and is assembled in a manner that straddles the guide rail 2. The block 3 includes a block body 4 that serves as the main body of the moving member, and a pair of cover members 5a and 5b mounted on both end faces of the block body 4 in the moving direction. A load ball rolling groove 4a that faces the ball rolling groove 2a of the guide rail 2 is formed in the block body 4, and a return path 12 parallel to the load ball rolling groove 4a is formed. The cross-sectional shape of the load ball rolling groove 4a is a single arc or a pointed arch. 4c is a threaded hole for mounting a movable body such as a workbench on the block body 4, and 6a and 6b are sealing members.

[0028] Figure 2 A cross-sectional view showing the circulation path is shown. The circulation path is composed of a load path 11, a return path 12, and a U-shaped direction conversion path 13 that connects the load path 11 and the return path 12. A plurality of balls 7 are arranged in the circulation path. When the block 3 moves relative to the guide rail 2, the balls 7 circulate in the circulation path. The load path 11 is formed between the ball rolling groove 2a and the load ball rolling groove 4a. In the load path 11, the balls 7 are in a loaded state and bear preload, the load of the movable body, etc. The return path 12 is formed in the block body 4. The direction conversion path 13 is formed in the cover members 5a and 5b. The inner diameters of the return path 12 and the direction conversion path 13 are slightly larger than the diameter of the ball 7. In the return path 12 and the direction conversion path 13, the balls 7 are in an unloaded state.

[0029] Figure 3 and Figure 4 A perspective view of the cover member 5a as viewed from the side of the block body 4 is shown. In Figure 3 and Figure 4 , the viewing direction of the cover member 5a is changed for easy understanding. As Figure 3 shown, four direction conversion paths 13 are formed in the cover member 5a. 13a is one end portion of the direction conversion path 13 connected to the load path 11, and 13b is the other end portion of the direction conversion path 13 connected to the return path 12. The cover member 5a and the cover member 5b (refer to Figure 1 ) have the same shape.

[0030] The cover member 5a includes a cover body 8 that forms the outer peripheral side of the direction conversion path 13, and inner peripheral side members 9a and 9b that form the inner peripheral side of the direction conversion path 13. The cover body 8 is in an inverted U shape when viewed from the front, similar to the block body 4 of the block 3. The inner peripheral side members 9a and 9b are fitted into the concave portions of the left and right sleeve portions 8-1 of the cover body 8.

[0031] Figure 5A perspective view showing the inner peripheral side member 9a. On the inner peripheral side of the inner peripheral side member 9a, upper and lower direction conversion paths 13 are formed. The inner peripheral side of the direction conversion path 13 is formed in an arc shape in cross section and is integrally formed in an inverted U shape. At the end portion 13a on the load path 11 side of the upper direction conversion path 13, a rolling surface 21 composed of a flat surface is formed in a portion close to the ball rolling groove 2a (refer to Figure 3 (b)). The inner peripheral side member 9a is symmetric up and down. A rolling surface 21 is also formed at the end portion 13a on the load path 11 side of the lower direction conversion path 13. The inner peripheral side member 9a is symmetric left and right with the inner peripheral side member 9b (refer to Figure 3 (a)). The same rolling surface 21 as that of the inner peripheral side member 9a is also formed on the inner peripheral side member 9b.

[0032] Figure 3 (b) is Figure 3 An enlarged view of part b of (a). 2 is a guide rail, 2a is a ball rolling groove, 8 is a cover body, 9a is an inner peripheral side member, and 21 is a rolling surface. When the ball 7 enters the load path 11 from the direction conversion path 13, the ball 7 transfers from the rolling surface 21 of the inner peripheral side member 9a to the ball rolling groove 2a of the guide rail 2. On the other hand, when the ball 7 enters the direction conversion path 13 from the load path 11, the ball 7 contacts the contact portion 8a of the cover body 8 (also refer to Figure 4 ), and is guided by the contact portion 8a toward the rolling surface 21 side and transfers from the ball rolling groove 2a to the rolling surface 21. It should be noted that a wedge-shaped scooping portion can also be provided on the cover body 8 within the width of the ball rolling groove 2a, and the ball 7 is scooped up by the scooping portion.

[0033] 22 is the edge of the ball rolling groove 2a. The ball rolling groove 2a is formed as a concave curved surface with an arc shape in cross section up to this edge 22. On the outside of the edge 22 ( Figure 3 the lower side of (b)), a convex curved surface 23 with an arc shape in cross section continuous with the edge 22 is formed. On the outside of the convex curved surface 23 ( Figure 3 the lower side of (b)), an inclined surface 24 is formed.

[0034] Figure 6 It is a view (a cross-sectional view of the guide rail 2 and the block body 4) showing the contact angle lines L1 and L2 of the motion guiding device 1. The contact angle lines L1 and L2 indicate the directions in which the motion guiding device 1 can bear loads. The contact angles δ1 and δ2 are the angles formed by the contact angle lines L1 and L2 with the horizontal line H. The contact angles δ1 and δ2 can be appropriately changed according to the use of the motion guiding device 1. It should be noted that the direction of the direction conversion path 13 is different from the directions of the contact angle lines L1 and L2. This is to reduce the vertical dimension of the block body 4. The directions of the contact angle lines L1 and L2 can also be made consistent with the direction of the direction conversion path 13.

[0035] Figure 7Cross-sectional view of the motion guide device 1 orthogonal to the longitudinal direction of the guide rail 2 (cross-sectional view of the motion guide device 1 at the boundary X (refer to Figure 2 ) between the block body 4 and the cover member 5a). 2 is the guide rail, 2a is the ball rolling groove, 9a is the inner peripheral side member, and 21 is the rolling surface.

[0036] When the radius of curvature of the ball rolling groove 2a is set to R and the distance from the ball center O to the rolling surface 21 of the inner peripheral side member 9a is set to r, it is set that R > r. Here, R > r means that the rolling surface 21 exists at a position inside the extension line 2a1 of the ball rolling groove 2a. This is to prevent the ball from contacting the edge 22 of the ball rolling groove 2a.

[0037] Figure 8 (a) of shows the present embodiment in which R > r is set, Figure 8 (b) of shows the prior art in which R < r is set. As Figure 8 (b) of shows, in the prior art, since R < r is set, the rolling surface 21 exists at a position outside the extension line 2a1 of the ball rolling groove 2a ( Figure 8 (lower side of (b) of). Therefore, when the ball 7 transfers from the rolling surface 21 to the ball rolling groove 2a, the ball 7 contacts the edge 22 of the ball rolling groove 2a. At this time, the ball 7 is supported by the contact point 31 on the rolling surface 21 and the edge 22. On the other hand, as Figure 8 (a) of shows, in the present embodiment, since R > r is set, the rolling surface 21 exists at a position inside the extension line 2a1 of the ball rolling groove 2a. The rolling surface 21 existing inside is indicated by diagonal lines. When the ball 7 transfers from the rolling surface 21 to the ball rolling groove 2a, the ball 7 is supported by the contact point 31 on the rolling surface 21 and the contact point 32 on the ball rolling groove 2a, so that contact with the edge 22 of the ball rolling groove 2a can be prevented.

[0038] It should be noted that, as Figure 7 shows, the ball center O is the center O of the ball 7 in the unloaded state in contact with the ball rolling groove 2a and is located on the contact angle line L1. Since the radius of curvature R of the ball rolling groove 2a is mostly set to 51 - 53% of the diameter of the ball 7, the curvature center C of the ball rolling groove 2a is slightly offset from the ball center O. In Figure 7 , this offset is exaggeratedly shown.

[0039] Figure 9 Similar to Figure 7 shows a cross-sectional view of the motion guide device 1 orthogonal to the longitudinal direction of the guide rail 2. 2 is the guide rail, 2a is the ball rolling groove, 9a is the inner peripheral side member, and 21 is the rolling surface.

[0040] On the basis of satisfying the above condition of R > r, when the angle formed by the straight line L3 connecting the center of curvature C of the rolling groove 2a of the connecting ball and the edge 22 of the rolling groove 2a of the ball and the vertical line V is set as γ, and the angle formed by the rolling surface 21 of the inner peripheral side member 9a and the horizontal line H is set as θ, it is set that θ > γ. This is to ensure the clearance between the ball 7 at the nominal position and the rolling surface 21. The inner peripheral side member 9a is mostly a resin molded part, and dimensional errors are inevitably generated. By setting θ > γ and ensuring this clearance, the dimensional errors of the inner peripheral side member 9a can be tolerated.

[0041] This will be described in detail. Figure 9 The state where the ball 7 moves from the nominal position to the vicinity of the edge 22 of the rolling groove 2a of the ball while being in contact with the rolling groove 2a of the ball is shown. The nominal position is the position when the center O of the ball is located on the contact angle line L1 (refer to Figure 7 ). As Figure 9 shown, when it is set that R > r, before the ball 7 moves from the nominal position to the edge 22 of the rolling groove 2a of the ball (to the right of Figure 9 ), the ball 7 contacts the rolling surface 21. On the contrary, when the ball 7 moves from the vicinity of the edge 22 of the rolling groove 2a of the ball to the nominal position (to the left of Figure 9 ), a clearance is generated between the ball 7 and the rolling surface 21. Setting θ > γ and increasing the angle of θ is to ensure this clearance.

[0042] In contrast, when it is set that θ < γ (making the rolling surface 21 horizontal or nearly horizontal), even when the ball 7 moves from the vicinity of the edge 22 of the rolling groove 2a of the ball to the nominal position (to the left of Figure 9 ), the clearance between the ball 7 and the rolling surface 21 cannot be ensured. This is because when the rolling surface 21 is horizontal or nearly horizontal, the rolling surface 21 exists near the lowest point of the ball 7, so even when the ball 7 moves to the left of Figure 9 , the clearance hardly changes. In this case, when dimensional errors occur in the inner peripheral side member 9a, there is a possibility that the ball 7 interferes with the rolling surface 21 and the ball 7 cannot circulate.

[0043] The structure of the present embodiment has been described above. However, the present invention is not limited to being embodied as this embodiment, and can be embodied as other embodiments within the scope of not changing the gist of the present invention. For example, in the present embodiment, the inner peripheral side of the direction conversion path is formed on the inner peripheral side member, but it can also be formed on the lid body.

[0044] This specification is based on Japanese Patent Application No. 2020-087900 filed on May 20, 2020. The entire content is incorporated herein.

[0045] Description of Reference Numerals

[0046] 1... Motion guiding device, 2... Guide rail (track member), 2a... Ball rolling groove, 3... Block (moving member), 4... Block body (moving member body), 4a... Load ball rolling groove, 5a, 5b... Cover members, 7... Ball, 8... Cover body, 9a, 9b... Inner peripheral side members (inner peripheral side of the direction conversion path), 11... Load path, 12... Return path, 13... Direction conversion path, 21... Rolling surface, 22... Edge of the ball rolling groove, O... Ball center, C... Curvature center of the ball rolling groove, L3... Straight line connecting the curvature center of the ball rolling groove and the edge of the ball rolling groove, V... Plumb line, H... Horizontal line.

Claims

1. A motion guiding device, comprising: An orbital member having a ball rolling groove; and a moving member that is assembled to be relatively movable with respect to the rail member, wherein the moving member includes: a moving member main body having a load ball rolling groove opposed to the ball rolling groove and a return path substantially parallel to the load ball rolling groove; and a cover member having a direction conversion path connecting the load path between the ball rolling groove and the load ball rolling groove and the return path, a plurality of balls are arranged in a circulation path constituted by the load path, the return path, and the direction conversion path, characterized in that in a cross-sectional view of the motion guiding device orthogonal to the longitudinal direction of the rail member, when the radius of curvature of the ball rolling groove is set to R and the distance from the center of the ball to the rolling surface on the inner peripheral side of the direction conversion path is set to r, it is set that R>r, the rolling surface is located at a position closer to the inside than the extension line of the ball rolling groove.

2. The motion guiding device according to claim 1, characterized in that when the angle formed by the straight line connecting the center of curvature of the ball rolling groove and the edge of the ball rolling groove and the vertical line is set to γ and the angle formed by the rolling surface and the horizontal line is set to θ, it is set that θ>γ.

3. The motion guiding device according to claim 1 or 2, characterized in that the cover member includes a cover main body forming the outer peripheral side of the direction conversion path and an inner peripheral side member forming the inner peripheral side of the direction conversion path, the rolling surface on the inner peripheral side of the direction conversion path is formed on the inner peripheral side member.

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