Linear guide

Abstract

To provide a linear guide which can maintain the stable operation performance of a ball with a hole diameter of a ball return path maximized.SOLUTION: When an opening part at a side at which the opening part is connected to a load rolling path 24 out of both opening parts of a direction conversion path 26 is defined to be a rail-side opening part 28, and an opening part at a side at which the opening part is connected to a ball return path 23 is defined to be a return-path side opening part 29, an inside recessed groove 41, which defines an internal peripheral face of the direction conversion path 26, has cross section shapes different between at the rail-side opening part 28 and at the return-path side opening part 29 on respective planes orthogonal to a center axial line CL of the direction conversion path 26, and in an arbitrary cross section parallel with a plane along the center axial line of the direction conversion path, points of the inside recessed groove at both of the opening parts are connected to each other by a single circular arc or a plurality of smoothly-continuing circular arcs.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a linear guide, and more particularly to a linear guide that uses balls as rolling elements. [Background technology]

[0002] For example, a linear guide used in a machine tool or the like generally includes a guide rail with rail-side rolling grooves on its left and right side surfaces, a slider with slider-side rolling grooves provided at positions facing the rail-side rolling grooves of the guide rail, a load rolling path formed by the rail-side rolling groove and the slider-side rolling groove, and a large number of balls as rolling elements that are filled in ball return paths (hereinafter also referred to as "return holes") that are holes provided inside the slider and can roll in these rolling paths. End caps are attached to both axial ends of the slider, and direction change paths are formed inside the end caps to change the direction of the balls. The balls roll in the rolling paths, causing the slider to move relative to the guide rail in the axial direction. After rolling in the rolling paths, the balls change direction inside the end caps and return to their original positions through return holes formed inside the slider.

[0003] In a linear guide configured in this manner, the operating performance, which indicates the fluctuation of the dynamic friction force of the slider, and the vibration performance of the slider are greatly affected by the direction change path, and therefore various improvements have been made to date. For example, in Patent Documents 1 and 2, a smoothly inclined chamfer (straight section) is provided on the direction change path at the entrance / exit section where the ball enters the load area. In Patent Document 3, a chamfer is provided on the entrance / exit section of the inner peripheral surface of the direction change path, and an extension section is provided to guide the ball into the slider.

[0004] According to Patent Documents 1 to 3, the chamfering action can reduce the play of the ball that occurs between the direction change path and the load rolling path at the entrance and exit sections, which may reduce the vibration that occurs when the ball collides with the rail. However, at the connection point between the linear chamfer and the curved section inside the direction change path, the ball itself is forced to change from simple arc motion to linear motion, which may cause the ball's movement to become unstable and reduce operating performance.

[0005] In addition, in Patent Documents 4 and 5, the direction change path is configured with multiple arcs. This is because the movement of the rolling ball tends to become unstable at the entrance and exit sections, so an optimal design is possible, such as using a gently curved shape and reducing the curvature of the curved shape in areas where the movement of the ball is likely to be stable, and improved operating performance is expected. However, because it is not possible to reduce the play of the ball that occurs between the direction change path and the load rolling path, vibration caused by the ball colliding with the rail can become a problem.

[0006] Furthermore, in conventional linear guides, the cross-sectional shape of the return hole and the cross-sectional shape of the load rolling path are essentially the same single circle. In Patent Documents 1 to 3, the entrance and exit sections are chamfered, so as a result, only the entrance and exit sections do not have the same shape as the return hole, but the return hole is formed as a single circle up to the chamfer. The return hole connecting to the direction change path is formed by drilling in the metal part. In this case, the ratio (L / d) of the workable length L to the hole diameter d is approximately 25 to 50. Even if drilling were possible, the return hole would still need to have a certain degree of straightness. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-304045 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-182745 [Patent Document 3] Japanese Patent Application Publication No. 2018-71592 [Patent Document 4] Patent No. 3143604 [Patent Document 5] Special Publication No. 5-26043 Summary of the Invention [Problem to be solved by the invention]

[0008] Recently, there has been a trend toward longer sliders to improve the precision and rigidity of linear guides. When machining a return hole precisely into a long slider, it is advantageous to have a slightly larger diameter return hole. However, forming a direction change path with a larger diameter to match the return hole results in increased ball play in the circulation path near the entry / exit section, causing the ball to move around wildly in the circulation path, resulting in instability and deteriorating operational and vibration performance. There is also the possibility that the ball may collide with the land portion of the rolling groove on the slider or rail. Because the land portion of the rolling groove is convex, the contact stress is high when the ball collides, and fatigue failure is likely to occur in this area.

[0009] Patent Documents 1 to 5 assume that the hole diameters of the return hole and the load rolling path are the same, and do not consider the above-mentioned problem. In conventional linear guides, the hole diameter of the return hole needs to be set within a range that prevents the balls from colliding with the land portion of the ball groove so as to prevent large play in the circulation path at the inlet / outlet portion, making it difficult to meet the requirements of recent long sliders. When the hole diameter of the return hole needs to be increased due to reasons such as the slider being long or the straightness of the return hole being insufficient, a resin pipe may be inserted after the return hole is machined, but this increases the number of parts and complicates assembly.

[0010] The present invention has been made in response to the above-mentioned problems, and aims to provide a linear guide that can maximize the diameter of the return hole while maintaining stable operating performance. [Means for solving the problem]

[0011] Therefore, the above object of the present invention is achieved by the following configuration (1) relating to a linear guide. can be. (1) A guide rail having a rail-side rolling groove extending in the axial direction on its side surface; The guide rail is mounted so as to straddle the guide rail, and together with the rail-side rolling groove, the guide rail forms a load rolling path. a slider-side rolling groove that is substantially the same as the slider-side rolling groove; parallel The ball return path formed in a slider that is movable relative to the guide rail in the axial direction; The slider is fixed to the end surface in the moving direction thereof, and connects the load rolling path and the ball return path. an end cap having an outer groove defining an outer periphery of a connecting turning path; A slider is interposed between the slider and the end cap, and defines an inner peripheral surface of the direction-changing path. a return guide having an inner groove for receiving the return guide; The slider moves through the load rolling path, the ball return path, and the direction change path. A linear guide having a plurality of balls that roll together, Of the two openings of the direction change path, the opening on the side connected to the load rolling path is on the rail side. When the opening connected to the ball return path is defined as the return path side opening, The inner groove has a cross-sectional shape in a plane perpendicular to the central axis of the direction change path that is The opening and the return path side opening are different, and the plane is along the central axis of the direction change path. In any cross section parallel to the line 1, the points of the inner groove at both openings are defined as a single arc, or is a linear guide formed by connecting multiple smoothly continuous arcs. [Effects of the Invention]

[0012] According to the linear guide of the present invention, the inner groove that defines the inner surface of the direction change path has a cross-sectional shape in a plane perpendicular to the central axis of the direction change path that differs between the rail side opening and the return path side opening, and the cross-sectional shape in a plane along the central axis of the direction change path is a single arc or a series of smoothly continuous arcs, so that stable operating performance can be maintained while maximizing the hole diameter of the ball return path. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing a linear guide according to an embodiment of the present invention; [Figure 2] 2 is a schematic top view of the linear guide shown in FIG. 1 with a portion of the top surface thereof cut away. [Figure 3] FIG. 10 is a perspective view of an end cap with a return guide attached thereto. [Figure 4] FIG. 2 is an exploded perspective view of an end cap and a return guide. [Figure 5] FIG. [Figure 6] 6A is a partial side view showing the inner grooves of the rail-side opening and the return path-side opening of the return guide, and FIG. 6B is a cross-sectional view taken along the line VI-VI of FIG. 6A. [Figure 7] 7A is a partial side view showing inner recessed grooves of a rail-side opening and a return path-side opening of a return guide of a first modified example, and FIG. 7B is a cross-sectional view taken along line VII-VII of FIG. 7A. [Figure 8] 8(a) is a partial side view showing inner recessed grooves of a rail-side opening and a return path-side opening of a return guide of a second modified example, and FIG. 8(b) is a cross-sectional view taken along the line VIII-VIII of FIG. 8(a). DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the linear guide according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiment described below, and can be implemented with any modifications within the scope of the gist of the present invention.

[0015] 1 and 2, the linear guide 1 of this embodiment includes a guide rail 3 extending in one direction, and a slider 20 with a C-shaped cross section that is attached to straddle the guide rail 3 and is movable in the axial direction relative to the guide rail 3. In this embodiment, the front-rear direction refers to the direction in which the slider 20 moves along the guide rail 3, and the left-right direction refers to the width direction of the slider 20 attached to the guide rail 3.

[0016] The guide rail 3 is made of metal, and on each of the left and right side surfaces 3b thereof, two rail-side rolling grooves 5 are formed along the axial direction of the guide rail 3. The guide rail 3 has a plurality of rail mounting holes 4 penetrating the guide rail 3 in the height direction, and rail fixing bolts 6 are inserted into these rail mounting holes 4 to fix the guide rail 3 to a mounting surface (not shown).

[0017] As shown in Figures 1 to 4, the slider 20 comprises a slider body 21 having sleeve portions on both the left and right sides of the guide rail 3, a pair of end caps 30, 30 attached to both ends of the slider body 21 in the front-to-rear direction, return guides 40, 40 incorporated into each of these end caps 30, 30, and a pair of side seals 50, 50 that seal the gap between the guide rail 3 and the end caps 30, 30.

[0018] The slider body 21 has a slider-side rolling groove 22 and a ball return path 23 on both the left and right sides. The slider-side rolling groove 22 is formed on the inner surfaces of both sleeve portions of the slider body 21 and faces the rail-side rolling groove 5, and the rail-side rolling groove 5 and the slider-side rolling groove 22 form a load rolling path 24. The ball return path 23 is formed by a hole that penetrates the thick portions of both sleeve portions in the axial direction of the guide rail 3. In addition, a driven body fixing screw insertion hole 25 is provided on the top surface of the slider body 21, through which a bolt that fixes a driven body such as a table to the slider 20 is inserted.

[0019] The end caps 30 joined to the front and rear ends of the slider body 21 are, for example, injection-molded products made of synthetic resin, and are formed with a C-shaped cross section similar to the slider body 21. The end caps 30 are provided with a plurality of mounting screw insertion holes 34, and the end caps 30, together with the side seals 50, are fastened to the end face 21a of the slider body 21 by mounting screws 35 inserted into the mounting screw insertion holes 34.

[0020] In addition, on the left and right sleeve portions 31 of the end cap 30, outer grooves 32 which are semi-disk-shaped recesses are formed in two upper and lower stages on the abutment surface 31a side against both front and rear end faces 21a of the slider body 21, and fitting recesses 33 are formed at positions crossing the widthwise center of the upper and lower two-stage outer grooves 32.

[0021] Referring also to Figure 5, the return guide 40 is formed in a semi-cylindrical shape, and on the outer diameter surface of the return guide 40, inner grooves 41, which are semi-disk-shaped recesses that serve as guide surfaces for the balls 51, are formed in two upper and lower stages continuously in the circumferential direction.

[0022] 3 and 4, the return guide 40 is attached to the end cap 30 by fitting it into the fitting recess 33 with the outer diameter surface on which the inner groove 41 is formed facing inward. As a result, the inner groove 41 of the return guide 40 and the outer groove 32 of the end cap 30 form a semi-donut-shaped (curved tubular) direction change path 26 in two stages, upper and lower, on both the left and right sides of the back surface of the end cap 30.

[0023] The return guide 40 is manufactured by injection molding of resin and metal, or by using a 3D printer. Possible resin materials include engineering plastics such as polyacetal, polyamide, and PEEK materials, which may be reinforced with approximately 2 to 50% glass fiber or carbon fiber. Possible metal materials include austenitic stainless steels such as SUS304 and SUS316. It is also possible to form the return guide 40 by cutting resin or metal materials.

[0024] As a result, the direction change path 26 communicates the load rolling path 24 and the ball return path 23, and the load rolling path 24, the ball return path 23, and the direction change path 26 form a ball rolling path 27 (see FIG. 2). A plurality of balls 51 made of steel, for example, are loaded in the ball rolling path 27, and these plurality of balls 51 circulate endlessly while rolling within the ball rolling path 27 as the slider 20 moves relative to the slider 20.

[0025] Next, the direction change path 26, and in particular the inner recessed groove 41 of the return guide 40, will be described in detail with reference to Figures 6(a) and (b). Of the two openings of the direction change path 26, the opening on the side connected to the load rolling path 24 is referred to as the rail-side opening 28, and the opening on the side connected to the ball return path 23 is referred to as the return path-side opening 29. In Figures 3 to 5, the direction change path 26 has rail-side opening 28 and return path-side opening 29 at different heights in the up-down direction, but in Figures 6 to 8, for the sake of simplicity, they will be described as being at the same height.

[0026] 6(a), the cross-sectional shapes of the inner groove 41 of the return guide 40 in a plane perpendicular to the central axis CL of the direction changing path 26 differ between the rail-side opening 28 and the return path-side opening 29. That is, the inner groove 41a of the rail-side opening 28 and the inner groove 41b of the return path-side opening 29 both have a single arc shape, but the radius R1 of the inner groove 41b of the return path-side opening 29 is larger than the radius R2 of the inner groove 41a of the rail-side opening 28.

[0027] The inner groove 41 is formed so that a single arc connects the points of the inner grooves 41a and 41b at both openings 28 and 29 in any cross section parallel to a plane along the central axis CL of the direction change path 26.

[0028] For example, as shown in Figure 6(b), in a cross section (VI-VI cross section) passing through the central axis CL of the direction change path 26, the groove bottom of the inner groove 41 smoothly connects point P1 of the inner groove 41a of the rail side opening 28 and point P2 of the inner groove 41b of the return path side opening 29 in a single arc of radius R3.

[0029] When the distance from the widthwise center line CL2 of the return guide 40 to the bottom of the inner groove 41a of the rail side opening 28 is d2 and the distance from the center line CL2 to the bottom of the inner groove 41b of the return path side opening 29 is d3, the radius R3 is R3 = (d2 + d3) / 2, and the center O3 of the arc of radius R3 is offset toward the rail side opening 28 by d1 = (d3 - d2) / 2.

[0030] In addition, in any cross section parallel to a plane along the central axis CL of the direction change path 26, the portion larger than the inner recess 41a of the rail side opening 28 also connects the point of the inner recess groove 41 closest to the rail side opening 28 and the point of the inner recess groove 41b of the return path side opening 29 by a single arc.

[0031] Thus, the inner groove 41a of the rail-side opening 28 and the inner groove 41b of the return path-side opening 29 are each formed in an arc shape, with the radius R1 of the inner groove 41b of the return path-side opening 29 being greater than the radius R2 of the inner groove 41a of the rail-side opening 28. Furthermore, the inner groove 41 is formed so that a single arc connects points of the inner groove 41 at both openings 28, 29 in any cross section parallel to a plane along the central axis CL of the direction change path 26. This allows the hole diameter of the ball return path 23 to be increased, facilitating its machining. This improves the straightness of the ball return path 23 even in a long slider, thereby maintaining stable operation performance of the ball 51. Furthermore, the inner groove 41a of the rail-side opening 28 is formed as an arc with a radius R2 smaller than the radius R1, thereby reducing the clearance within the ball rolling path 27 near the entrance and exit.

[0032] In addition, in the cross-sectional shape in a plane perpendicular to the central axis CL of the direction change path 26, when viewed in terms of the cross-sectional area formed by connecting both ends 41c, 41d of the inner groove, the cross-sectional area A2 of the return path side opening 29 is larger than the cross-sectional area A1 of the rail side opening 28. The inner recessed groove 41 is formed so that the cross-sectional area increases smoothly from the rail-side opening 28 to the return path-side opening 29.

[0033] In addition, the outer groove 32 may have different shapes for the rail side opening 28 and the return path side opening 29 so as to be continuous with the inner groove 41, or the return path side opening 29 may be formed as a single arc across the direction change path 26.

[0034] In the linear guide 1 configured in this manner, the hole diameter of the ball return path 23 can be maximized while maintaining stable operating performance.

[0035] Hereinafter, each of the modified examples of the return guide 40 will be described with reference to FIGS.

[0036] (First Modification) 7(a), in a cross section taken along a plane perpendicular to the central axis CL of the direction changing path 26, the inner groove 41 of the return guide 40 of the first modified example has an inner groove 41a at the rail-side opening 28 in the shape of a Gothic arch with a radius R2, and an inner groove 41b at the return path-side opening 29 formed from a single circular arc with a radius R1. The radius R1 of the inner groove 41b at the return path-side opening 29 is larger than the radius R2 of the inner groove 41a at the rail-side opening 28.

[0037] The inner groove 41 is formed so that a single arc connects the points of the inner grooves 41a and 41b at both openings 28 and 29 in any cross section parallel to a plane along the central axis CL of the direction change path 26.

[0038] 7(b), in a cross section (VII-VII cross section) passing through the central axis CL of the direction change path 26, point P1 of the Gothic arch shape of radius R2 of the inner groove 41a at the rail-side opening 28 and point P2 of the arc shape of radius R1 of the inner groove 41b at the return path-side opening 29 are smoothly connected by a single arc of radius R3. The shape of the inner groove 41 smoothly changes in the circumferential direction of the inner groove 41 from the Gothic arch shape of the inner groove 41b to the arc shape of the inner groove 41a.

[0039] When the distance from the widthwise center line CL2 of the return guide 40 to the bottom of the inner groove 41a of the rail side opening 28 is d2 and the distance from the center line CL2 to the bottom of the inner groove 41b of the return path side opening 29 is d3, the radius R3 is R3 = (d2 + d3) / 2, and the center O3 of the arc of radius R3 is offset toward the rail side opening 28 by d1 = (d3 - d2) / 2.

[0040] In this case too, when viewed in cross section in a plane perpendicular to the central axis CL of the direction change path 26, the cross-sectional area formed by connecting both ends 41c, 41d of the inner groove is such that the cross-sectional area A2 of the return path side opening 29 is larger than the cross-sectional area A1 of the rail side opening 28. The inner recessed groove 41 is formed so that the cross-sectional area increases smoothly from the rail-side opening 28 to the return path-side opening 29.

[0041] When the rail-side rolling groove 5 of the guide rail 3 is formed in a Gothic arch shape, it is preferable that the inner recessed groove 41a of the rail-side opening 28 also be formed in a Gothic arch shape, which reduces the step between the components and enables smoother circulation of the balls 51. In this way, the direction change paths 26 are smoothly connected by an arc of radius R3, allowing the balls 51 to move stably.

[0042] Patent Document 3 also proposes simultaneous grinding of the direction change path and ball groove, but when simultaneously grinding, the direction change path itself has a curved surface shape portion and an inflection point in the simultaneously ground portion, and there is a concern that burrs may be generated near this inflection point, causing malfunction. The linear guide 1 of this modified example does not have such problems and can reduce the steps between parts.

[0043] (Second Modification) 8(a), in the return guide 40 of the second modified example, in a cross section taken along a plane perpendicular to the central axis CL of the direction changing path 26, the inner groove 41a of the rail-side opening 28 has a Gothic arch shape with a radius R2, and the inner groove 41b of the return path-side opening 29 is formed from a single circular arc with a radius R1, similar to the linear guide of the first modified example. The radius R1 of the inner groove 41b of the return path-side opening 29 is larger than the radius R2 of the inner groove 41a of the rail-side opening 28.

[0044] The inner groove 41 is formed so that a single arc connects the points of the inner grooves 41a and 41b at both openings 28 and 29 in any cross section parallel to a plane along the central axis CL of the direction change path 26.

[0045] For example, as shown in Figure 8(b), in a cross section (VIII-VIII cross section) passing through the central axis CL of the direction change path 26, the groove bottom of the inner groove 41 is smoothly connected by two arcs 42, 43 of radii R3 and R4, with point P1 of the Gothic arch shape of the inner groove 41a of the rail side opening 28 and point P2 of the inner groove 41b of the return path side opening 29 and radius R1.

[0046] Here, the arc 42 of radius R3 is continuously connected in a single arc shape to the inner recessed groove 41b of the return path-side opening 29. On the other hand, the arc 43 of radius R4 is continuously connected to the Gothic arch shape of radius R2 of the inner recessed groove 41a of the rail-side opening 28 as the Gothic arch shape changes (widens), and the arc 42 of radius R3 and the arc 43 of radius R4 are smoothly connected as a single arc and a Gothic arch shape at their junction.

[0047] In this case too, when viewed in cross section in a plane perpendicular to the central axis CL of the direction change path 26, the cross-sectional area formed by connecting both ends 41c, 41d of the inner groove is such that the cross-sectional area A2 of the return path side opening 29 is larger than the cross-sectional area A1 of the rail side opening 28. The inner recessed groove 41 is formed so that the cross-sectional area increases smoothly from the rail-side opening 28 to the return path-side opening 29.

[0048] In addition, as in the second modified example, the configuration in which the inner groove 41a of the return path side opening 29 and the inner groove 41b of the rail side opening 28 are smoothly connected by two arcs 42, 43 in a cross section passing through the central axis CL of the direction change path 26 can also be applied to the case in which the inner groove 41a of the return path side opening 29 and the inner groove 41b of the rail side opening 28 are in the shape of a single arc, as in the above embodiment.

[0049] The present invention is not limited to the above-described embodiment and modifications, and can be modified, improved, etc. as appropriate.

[0050] As described above, the present specification discloses the following: (1) A guide rail having a rail-side rolling groove extending in the axial direction on its side surface; The guide rail is mounted so as to straddle the guide rail, and together with the rail-side rolling groove, the guide rail forms a load rolling path. a slider-side rolling groove that is substantially the same as the slider-side rolling groove; parallel The ball return path formed in a slider that is movable relative to the guide rail in the axial direction; The slider is fixed to the end surface in the moving direction thereof, and connects the load rolling path and the ball return path. an end cap having an outer groove defining an outer periphery of a connecting turning path; A slider is interposed between the slider and the end cap, and defines an inner peripheral surface of the direction-changing path. a return guide having an inner groove for receiving the return guide; The slider moves through the load rolling path, the ball return path, and the direction change path. A linear guide having a plurality of balls that roll together, Of the two openings of the direction change path, the opening on the side connected to the load rolling path is on the rail side. When the opening connected to the ball return path is defined as the return path side opening, The inner groove has a cross-sectional shape in a plane perpendicular to the central axis of the direction change path that is The opening and the return path side opening are different, and the plane is along the central axis of the direction change path. In any cross section parallel to the cross section, the points of the inner groove at both openings are defined as a single arc, or is a linear guide formed by connecting multiple smoothly continuous arcs. This configuration maximizes the hole diameter of the ball return path while maintaining stable ball operation performance. can be maintained.

[0051] (2) In a cross section in a plane perpendicular to the central axis of the direction change path, the inner groove of the rail side opening and the inner groove of the return path side opening are each formed in an arc shape, with the radius R1 of the inner groove of the return path side opening being larger than the radius R2 of the inner groove of the rail side opening. This configuration allows the diameter of the ball return passage to be maximized while maintaining stable ball operation performance.

[0052] (3) A linear guide as described in (1), wherein, in a cross section in a plane perpendicular to the central axis of the direction change path, the inner groove of the rail side opening has a Gothic arch shape, and the inner groove of the return path side opening has a circular arc shape. This configuration allows the diameter of the ball return passage to be maximized while maintaining stable ball operation performance.

[0053] (4) In a cross-sectional shape in a plane perpendicular to the central axis of the direction-changing path, a cross-sectional area formed by connecting both ends of the inner groove is larger at the return path side opening than at the rail side opening, The linear guide according to any one of (1) to (3), wherein the inner groove is formed so that the cross-sectional area increases smoothly from the rail-side opening to the return path-side opening. This configuration allows the diameter of the ball return passage to be maximized while maintaining stable ball operation performance. [Explanation of symbols]

[0054] 1 Linear guide 3 Guide rails 3b Left and right sides 5 Rail side rolling groove 20 Slider 21 Slider body 21a End face (end face on the slider movement direction side) 22 Slider side rolling groove 23 Ball return path 24 Load rolling path 26 Turning Point 27 Ball rolling path 28 Rail side opening 29 Return road side opening 30 End Cap 32 Outer groove 40 Return Guide 41,41a,41b Inner groove 51 Ball CL Central axis of turning path R1 Radius of inner groove of return passage opening R2 Radius of the inner groove of the rail side opening

Claims

1. a guide rail having a rail-side rolling groove extending in the axial direction on a side surface; a slider attached to the guide rail so as to straddle the guide rail, the slider having a slider-side rolling groove that forms a loaded rolling path together with the rail-side rolling groove, and a ball return path formed substantially parallel to the slider-side rolling groove, the slider being movable in the axial direction relative to the guide rail; an end cap fixed to an end surface of the slider in the moving direction, the end cap having an outer groove that defines an outer peripheral surface of a direction change path that connects the load rolling path and the ball return path; a return guide interposed between the slider and the end cap and having an inner groove defining an inner circumferential surface of the direction-changing path; a plurality of balls that roll in the load rolling path, the ball return path, and the direction changing path in accordance with movement of the slider, When, of the two openings of the direction changing path, the opening connected to the loaded rolling path is defined as a rail-side opening, and the opening connected to the ball return path is defined as a return-path-side opening, the cross-sectional shapes of the inner groove in a plane perpendicular to the central axis of the direction changing path are different between the rail-side opening and the return-path-side opening, and the inner groove is formed so that, in any cross section parallel to the plane along the central axis of the direction changing path, points of the inner groove at both openings are connected by a single arc or a plurality of smoothly continuous arcs, In a cross section taken along a plane perpendicular to the central axis of the direction changing path, the inner groove of the rail-side opening and the inner groove of the return path-side opening are each formed in an arc shape such that a radius R1 of the inner groove of the return path-side opening is larger than a radius R2 of the inner groove of the rail-side opening, The inner groove is a guide surface for the plurality of balls, and its cross-sectional shape in a plane perpendicular to the central axis of the direction change path is an arc shape that smoothly expands in diameter from the rail side opening to the return path side opening.

2. a guide rail having a rail-side rolling groove extending in the axial direction on a side surface; a slider attached to the guide rail so as to straddle the guide rail, the slider having a slider-side rolling groove that forms a loaded rolling path together with the rail-side rolling groove, and a ball return path formed substantially parallel to the slider-side rolling groove, the slider being movable in the axial direction relative to the guide rail; an end cap fixed to an end surface of the slider in the moving direction, the end cap having an outer groove that defines an outer peripheral surface of a direction change path that connects the load rolling path and the ball return path; a return guide interposed between the slider and the end cap and having an inner groove defining an inner circumferential surface of the direction-changing path; a plurality of balls that roll in the load rolling path, the ball return path, and the direction changing path in accordance with movement of the slider, When, of the two openings of the direction changing path, the opening connected to the loaded rolling path is defined as a rail-side opening, and the opening connected to the ball return path is defined as a return-path-side opening, the cross-sectional shapes of the inner groove in a plane perpendicular to the central axis of the direction changing path are different between the rail-side opening and the return-path-side opening, and the inner groove is formed so that, in any cross section parallel to the plane along the central axis of the direction changing path, points of the inner groove at both openings are connected by a single arc or a plurality of smoothly continuous arcs, In a cross section taken along a plane perpendicular to the central axis of the direction changing path, the inner groove of the rail-side opening has a Gothic arch shape, and the inner groove of the return path-side opening has a circular arc shape; The inner groove is a guide surface for the plurality of balls, and the cross-sectional shape in a plane perpendicular to the central axis of the direction change path smoothly changes from a Gothic arch shape to a circular arc shape from the rail side opening to the return path side opening.

3. In a cross-sectional shape in a plane perpendicular to the central axis of the direction changing path, a cross-sectional area formed by connecting both ends of the inner groove is larger at the return path side opening than at the rail side opening, The linear guide according to claim 1 or 2, wherein the inner groove is formed so that the cross-sectional area increases smoothly from the rail-side opening to the return path-side opening.

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