Linear motion guide device and manufacturing method therefor

Abstract

To provide a low cost linear motion guide device that can ensure a long life even when foreign matter is generated from each part under a normal use condition, and a manufacturing method therefor.SOLUTION: In a linear motion guide device, a raceway groove of a slider body has a first raceway surface on a center side of a rolling path and a second raceway surface on an end side of the rolling path, the second raceway surface has a chamfer part formed so as to intersect with an end surface of the slider body, the chamfer part has a tapered shape that gradually moves away from a center line of a straight part of the rolling path as it moves from the first raceway surface side toward the end surface of the slider body, the chamfer part is formed by cutting, and surface layers of at least the first raceway surface and the second raceway surface have a retained austenite content of 20% or more.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a linear guide device and a manufacturing method thereof. [Background technology]

[0002] Linear guide devices, which guide objects linearly while allowing rolling elements such as rollers and balls to circulate endlessly inside, are one of the important machine elements that have a significant impact on the motion accuracy of semiconductor manufacturing equipment, ultra-precision processing machines, ultra-precision measuring instruments, etc.

[0003] The linear guide device comprises a guide rail and a slider body. The guide rail is provided with rail-side rolling element raceway grooves. The slider body is provided with slider-side rolling element raceway grooves that face the rail-side rolling element raceway grooves, and the slider body is supported by the guide rail so as to be movable in the axial direction via the rolling of multiple rolling elements disposed in rolling paths formed between the slider-side rolling element raceway grooves and the rail-side rolling element raceway grooves. The linear guide device further comprises a rolling element return path provided in the slider body so as to be substantially parallel to the rolling path, and direction change paths provided in end caps attached to both ends of the slider body in the moving direction, which connect the rolling path and the rolling element return path.

[0004] In general linear motion guiding devices, improvements have been made to extend the spalling life, such as optimizing the heat treatment conditions for the components (optimizing the amount of retained austenite), as shown in Patent Document 1. However, the technology for leaving the amount of retained austenite in the final product is basically a technology for extending the life by suppressing the occurrence of spalling when foreign matter such as iron powder infiltrates the groove surface during use, and it is thought that its effect is small in a completely clean state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-110751 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a linear guide device and a manufacturing method thereof that are low cost and can ensure a long life even when foreign matter is generated from each part under normal use conditions. [Means for solving the problem]

[0007] The linear guide device of the present invention is Guide rails and a slider disposed so as to move relative to the guide rail in a longitudinal direction; a plurality of rolling elements arranged to roll freely along a rolling path formed between the guide rail and the slider, The slider includes: a slider body having raceway grooves disposed opposite the raceway grooves of the guide rail to form rolling paths for the rolling elements, and having return paths for the rolling elements; an end cap having a direction change passage connecting the return passage and the rolling passage, the raceway groove of the slider body has a first raceway surface on the central side of the rolling path and a second raceway surface on the end side of the rolling path, the second raceway surface has a chamfered portion formed so as to intersect with the end surface of the slider body, the chamfered portion has a tapered shape that gradually moves away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body, and the chamfered portion is formed by cutting; At least the surface layers of the first raceway surface and the second raceway surface have a retained austenite content of 20% or more.

[0008] The manufacturing method of the linear guide device of the present invention includes: Guide rails and a slider disposed so as to move relative to the guide rail in a longitudinal direction; a plurality of rolling elements that are arranged to roll freely along a rolling path formed between the guide rail and the slider, The slider includes: a slider body having raceway grooves disposed opposite the raceway grooves of the guide rail to form rolling paths for the rolling elements, and having return paths for the rolling elements; an end cap having a direction change passage connecting the return passage and the rolling passage, the raceway groove of the slider body has a first raceway surface on the central side of the rolling path and a second raceway surface on the end side of the rolling path, a chamfered portion having a tapered shape that gradually moves away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body is formed on the second raceway surface by cutting, At least the surface layers of the first raceway surface and the second raceway surface are heat treated so that the amount of retained austenite is 20% or more. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a linear guide device and a manufacturing method thereof that are low cost and can ensure a long life even if foreign matter is generated from each part under normal use conditions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a linear guide device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of the vicinity of an end portion of the slider body. [Figure 3] FIG. 3 is an enlarged view of the vicinity of the raceway groove. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is an enlarged schematic view of part V in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this specification, terms indicating directions (upward, downward, etc.) refer to the respective directions in Figure 2 unless otherwise specified. Furthermore, the "longitudinal direction" refers to the longitudinal direction of the guide rail or slider.

[0012] Fig. 1 is a perspective view showing a linear guide device according to an embodiment of the present invention, Fig. 2 is a perspective view showing the vicinity of an end of a slider body.

[0013] A slider 2 with a substantially U-shaped cross section is assembled along a linearly extending guide rail 1 with a substantially rectangular cross section so as to be movable in the longitudinal direction of the guide rail 1. At the ridge where both left and right side surfaces 1a, 1a in the width direction of the guide rail 1 intersect with the top surface 1b, track grooves 10B, 10B consisting of recessed grooves with a cross section shaped like a quarter of a circle are formed along the longitudinal direction.

[0014] Furthermore, raceway grooves 10A, 10A each consisting of a recessed groove with a substantially semicircular cross section are formed along the longitudinal direction in approximately the center in the vertical direction of both left and right side surfaces 1a, 1a in the width direction of the guide rail 1. Furthermore, at the groove bottom of the raceway grooves 10A, 10A, a retainer groove (wire groove) for guiding a retainer (not shown) is formed along the longitudinal direction between both ends of the movement area of ​​the slider 2 (for example, between both ends in the longitudinal direction of the guide rail 1).

[0015] The slider 2 comprises a slider body 2A and end caps 2B, 2B detachably attached to both ends (longitudinal ends) of the slider body 2A. Furthermore, side seals 5, 5 are attached to both ends of the slider 2 (longitudinal outer end faces of each end cap 2B) to seal the portion of the opening of the gap between the guide rail 1 and the slider 2 facing the longitudinal end faces, and an under seal (not shown) is attached to the bottom of the slider 2 to seal the portion of the opening of the gap between the guide rail 1 and the slider 2 facing the underside of the slider 2. These side seals 5, 5 and under seal prevent foreign matter from entering the gap from the outside and prevent lubricant from leaking from the gap to the outside.

[0016] 2, the slider body 2A is composed of a flat body 7 facing the upper surface 1b of the guide rail 1, and two legs 6, 6 extending downward from both the left and right sides of the body 7 and facing the side surface 1a, and the angle between the body 7 and the legs 6, 6 is approximately a right angle, so that the cross section of the slider body 2A is approximately U-shaped. Furthermore, the slider body 2A is attached movably relative to the guide rail 1, with the guide rail 1 sandwiched between the legs 6, 6.

[0017] Furthermore, raceway grooves 11A, 11A, 11B, 11B (hereinafter, 11 may be used as a general reference symbol) consisting of recessed grooves with a substantially semicircular cross section that face raceway grooves 10A, 10A, 10B, 10B (hereinafter, 10 may be used as a general reference symbol) of the guide rail 1 are formed at the corners and approximately the center in the vertical direction of the inner surfaces of both the left and right legs 6, 6 of the slider body 2A. Also, as shown in Fig. 1, rolling paths 13A, 13A, 13B, 13B (hereinafter, 13 may be used as a general reference symbol) with a substantially circular cross section are formed between the raceway groove 10 of the guide rail 1 and the raceway groove 11 of the slider 2, and these rolling paths extend in the longitudinal direction.

[0018] A plurality of rolling elements 3 (balls) are held by a cage and loaded in the rolling passage 13 so as to be able to roll freely, and the slider 2 is guided by the guide rail 1 and is able to move in the longitudinal direction via the rolling elements rolling in the rolling passage 13. The cage is formed of, for example, a wire, and holds the rolling elements 3 to prevent them from falling off the slider 2 before it is assembled to the guide rail 1.

[0019] The number of track grooves 10, 11 provided on the guide rail 1 and the slider 2 is not limited to two rows on one side, but may be, for example, one row on one side, or three or more rows. Also, the cross-sectional shape of the track grooves 10, 11 may be an arc shape consisting of a single arc as described above, or may be a substantially V-shape (Gothic arc groove) consisting of a combination of two arcs with different centers of curvature.

[0020] Furthermore, the slider 2 is provided with return passages 14A, 14A, 14B, 14B (hereinafter, the reference numeral 14 may be used to refer to these collectively) at the upper and lower parts of the thick portions of both the left and right leg portions 6, 6 of the slider body 2A, each of which is formed from a through-hole with an approximately circular cross section that penetrates in the longitudinal direction parallel to the rolling passage 13 (see Figures 1 and 2).

[0021] The end cap 2B is made of, for example, a molded product of a resin material, and has a substantially U-shaped cross section similar to the slider body 2A. Furthermore, on both the left and right sides of the back surface of the end cap 2B (the surface that abuts against the slider body 2A), two arc-shaped, upper and lower direction change paths 15 are formed (see FIG. 4, described later). When the end cap 2B is attached to the slider body 2A with fastening members such as screws, the direction change paths 15 connect the rolling path 13 and the return path 14. The cross-sectional shape of the direction change paths 15 is shown schematically in FIG. 4.

[0022] The return path 14 and the direction change paths 15 at both ends constitute a rolling element conveying path 16 that conveys and circulates the rolling elements 3 from the end point of the rolling path 13 to the start point, and the rolling path 13 and the rolling element conveying path 16 constitute a substantially circular circulation path. This substantially circular circulation path is formed in two levels, upper and lower, on both the left and right sides of the guide rail 1.

[0023] As the slider 2 moves longitudinally along the guide rail 1, the rolling elements 3 loaded in the rolling path 13 roll within the rolling path 13 and move in the same direction as the slider 2 relative to the guide rail 1. When the rolling elements 3 reach the end of the rolling path 13, they are scooped up from the rolling path 13 and sent to the direction change path 15. Having entered the direction change path 15, the rolling elements 3 change direction and are introduced into the return path 14, through which they reach the opposite direction change path 15, where they change direction again and return to the start of the rolling path 13. The rolling elements 3 repeat this circulation within the circulation path endlessly, allowing the slider 2 to move smoothly along the guide rail 1.

[0024] Fig. 3 is an enlarged view of the vicinity of the track groove 11A. Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 2, showing the slider 2 assembled to the guide rail 1. Fig. 5 is a schematic enlarged view of part V in Fig. 4.

[0025] The shapes of the ends of the raceway grooves 11A and 11B will be described with reference to the drawings. Since the raceway groove 11B has a shape that is almost the same as that of the raceway groove 11A, the following description will mainly focus on the raceway groove 11A, and a description of the raceway groove 11B will be omitted.

[0026] In the figure, the raceway groove 11A has a first raceway surface 11Aa on the center side of the slider body 2A and a second raceway surface 11Ab on both end sides of the slider body 2A. The first raceway surface 11Aa and the second raceway surface 11Ab are each bounded by a vertical centerline C1 (an imaginary line, see Figure 3) at the groove bottom, with the portion above the vertical centerline C1 referred to as the upper flank and the portion below the vertical centerline C1 referred to as the lower flank. The upper and lower flanks are symmetrical with respect to the vertical centerline C1. The vertical centerline C1 and the centerline O1 of the straight portion of the rolling path 13A are within a horizontal reference plane.

[0027] The first raceway surface 11Aa has a uniform cross section perpendicular to the longitudinal direction. The center line of the cylindrical space formed by the first raceway surface 11Aa and the raceway groove 10A of the guide rail 1 is set as the center line O1 of the straight portion of the rolling path 13A. In contrast, the second raceway surface 11Ab is formed so that the cross section perpendicular to the longitudinal direction varies partially.

[0028] The second raceway surface 11Ab has a symmetrical shape with respect to the vertical centerline C1. The second raceway surface 11Ab has a crowning portion 11Ac connected to the first raceway surface 11Aa and a chamfered portion 11Ad connected to the crowning portion 11Ac and intersecting with the end face 2Aa. The second raceway surface 11Ab on the other side of the slider body 2A has a similar shape.

[0029] The crowning portion 11Ac has a tapered shape that gradually moves away from the straight-line portion center line O1 toward the end face 2Aa of the slider body 2A. The chamfered portion 11Ad also has a tapered shape that gradually moves away from the straight-line portion center line O1 toward the end face 2Aa, but the inclination angle of the chamfered portion 11Ad with respect to the straight-line portion center line O1 is greater than the inclination angle of the crowning portion 11Ac with respect to the straight-line portion center line O1. Specifically, the difference between the distance from the boundary between the chamfered portion 11Ad and the crowning portion 11Ac to the straight-line portion center line O1 and the distance from the boundary between the first raceway surface 11Aa and the crowning portion 11Ac to the straight-line portion center line O1 is set to approximately 0.5% of the rolling element diameter.

[0030] By forming the chamfered portion 11Ad at the end of the raceway groove 11A in this manner, a step S1 is generated between the return guide 17 attached to the end face 2Aa of the slider body 2A and the raceway groove 11A, as shown in Fig. 4. In this embodiment, finishing such as polishing to round off the edges generated at the step S1 is not performed.

[0031] The return passage 14A, which constitutes the circulation path, has a diameter slightly larger than the diameter of the rolling elements, but the connecting portion with the end cap 2B is formed with a chamfered portion 14Ad by cutting to allow for misalignment. Because the chamfered portion 14Ad is formed, a step S2 is created between the end cap 2B and the return guide 17 and the return passage 14A. In this embodiment, finishing such as polishing to round the edges of the step S2 is not performed.

[0032] Furthermore, when the overall length of the return passage 14A is relatively long, cutting is often performed from both ends of the slider body 2A using opposing drills, but misalignment of the drill axes can result in a shape with a connecting step in the center, which can create a step S3 on the inner circumferential surface of the communicating part of the drilled hole. In this embodiment, finishing such as polishing to round off the edges of the step S3 is not performed.

[0033] If steps S1 to S3 exist at the connecting portion between the raceway groove 11A and the direction change path 15, at the connecting portion between the direction change path 15 and the return path 14, and at the connecting portion of the drilled holes in the return path 14, the edges of the steps are scraped off as the rolling elements 3 roll and circulate, generating foreign matter and making it more likely that the rolling elements 3 will become stuck. However, if processing is performed to remove the edges of the steps S1 to S3 in order to prevent such problems, this could extend the processing time or increase costs by adding parts.

[0034] Therefore, in the slider body 2A of this embodiment, the crowning portion 11Ac is formed by grinding or cutting to gradually increase or decrease the preload or load, and the chamfered portion 11Ad is formed by cutting, without performing finishing processing such as polishing to round the edges of the steps S1 to S3.

[0035] Specifically, since the continuity of the crowning portion 11Ac with the first raceway surface 11Aa is important, the crowning portion 11Ac is ground and finished continuously from the first raceway surface 11Aa using a grinding wheel that finishes the first raceway surface 11Aa.

[0036] On the other hand, the chamfered portion 11Ad is formed by cutting using a drill or a chamfering tool. By forming the chamfered portion 11Ad before the heat treatment described later, together with forming the crowning portion 11Ac, the processing time is shortened and the cost is reduced.

[0037] Generally, when a chamfered portion is formed by grinding, the volume of material removed (machining allowance) is relatively large, resulting in high costs. In this embodiment, the crowning portion 11Ac is formed by, for example, grinding, while the chamfered portion 11Ad is formed by cutting (for example, turning), thereby enabling low-cost machining.

[0038] Here, edges tend to form on both ends of the grinding or cutting surface, which must be removed after the grinding or cutting process. Conventional methods require manual polishing for finishing, which is time-consuming and increases costs. Therefore, in this embodiment, finishing is not performed, thereby reducing costs.

[0039] However, because the rolling elements in a linear guide device move at high speed within the circulation path, if there are steps, burrs, edges, etc. in the circulation path, they will peel off as the rolling elements pass through and become foreign matter (small iron powder, etc.), which will be crushed between the rolling groove and the rolling elements, damaging the rolling groove and rolling elements and potentially causing the rolling groove to peel off.

[0040] Ideally, there should be no steps or edges. However, even if burrs generated during processing are removed, measures such as manufacturing parts to reduce steps or rounding edges are costly. Therefore, in this embodiment, the amount of retained austenite (retained austenite volume fraction) is set to 20% or more by adjusting the heat treatment of the slider body 2A. In this way, increasing the amount of retained austenite can suppress peeling of the rolling grooves even in an environment where foreign matter is likely to be generated.

[0041] The advantage of increasing the amount of retained austenite to 20% or more is that it makes it less likely for the groove surface to peel (damage) in a foreign matter environment. Therefore, it is preferable to have the amount of retained austenite of 20% or more at least in the surface layers of the raceway groove 11A and the return passage 14A, and even more preferable to have the amount of retained austenite of 20% or more only in the surface layer of the raceway groove 11A. If possible, it is also preferable to have the amount of retained austenite of 20% or more in the raceway grooves 10A and 10B of the guide rail 1 and the rolling elements 3. However, since the rolling conditions in a linear guide device are the most severe, that is, the rolling elements 3 roll along the raceway grooves 11A (11B) under a load, it is preferable to increase the amount of retained austenite at least in the surface layer of the raceway groove 11A (11B).

[0042] In this embodiment, the crowning portion 11Ac is ground or machined, and the chamfered portion 11Ad is machined, thereby reducing costs. To ensure positional accuracy at both ends of the slider body 2A, the return passages 14A are machined using a drill from both ends, with the return passages 14A communicating at the center of the holes, and the allowable step height is 5% or less of the diameter of the rolling elements used.

[0043] Regarding the roughness of each part of the slider, the arithmetic mean roughness of the inner surface of the raceway groove 11A (11B) is Ra 0.2 to 1.6 (superfinishing is not required), and the arithmetic mean roughness of the surfaces of other circulation parts may be about Ra 6.3 obtained by cutting.

[0044] When a long stroke is required, multiple guide rails 1 are connected and used, but the end faces of the raceway grooves 10A, 10B of the guide rail 1 are only lightly chamfered without any special crowning. If the end faces of the raceway grooves 10A, 10B have burrs or the like that make them convex relative to the groove surface, this will hinder the rolling of the rolling elements and is unacceptable from a functional standpoint, so inexpensive light chamfering (for example, C0.3 or less) is used to remove the burrs (convex portions).

[0045] According to this embodiment, no special processing or parts are required, and the slider body 2A can be formed at low cost, and yet a linear guide device with a long life can be realized.

[0046] The present invention is not limited to the above-described embodiments, and the scope of protection includes the mutual combination of the configurations of the embodiments, and modifications and applications by those skilled in the art based on the description in the specification and well-known techniques. For example, the chamfered portion 11Ad may be directly connected to the first raceway surface 11Aa without providing a crowning portion. [Explanation of symbols]

[0047] 1 Guide rail 2 Slider 2A slider body 2B End Cap 3 Rolling elements 10A,10B Raceway groove 11A,11A raceway groove 13A,13B Rolling passage 14A, 14B Return passage 15 Turning Point

Claims

1. Guide rails and a slider disposed to move relative to the guide rail in a longitudinal direction; a plurality of rolling elements arranged to roll freely along a rolling path formed between the guide rail and the slider, The slider includes: a slider body having raceway grooves disposed opposite the raceway grooves of the guide rail to form rolling paths for the rolling elements, and having return paths for the rolling elements; an end cap having a direction change passage connecting the return passage and the rolling passage, the raceway groove of the slider body has a first raceway surface on the central side of the rolling path and a second raceway surface on the end side of the rolling path, the second raceway surface has a chamfered portion formed to intersect with the end surface of the slider body, the chamfered portion has a tapered shape that gradually moves away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body, and the chamfered portion is formed by cutting; At least the surface layers of the first raceway surface and the second raceway surface have a retained austenite amount of 20% or more. A linear guide device characterized by:

2. a crowning portion is formed between the first raceway surface and the chamfered portion, the crowning portion has a tapered shape that gradually moves away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body; 2. The linear guide device according to claim 1.

3. the arithmetic mean roughness of the first raceway surface is Ra 0.2 to 1.6; 2. The linear guide device according to claim 1.

4. Guide rails and a slider disposed to move relative to the guide rail in a longitudinal direction; a plurality of rolling elements that are arranged to roll freely along a rolling path formed between the guide rail and the slider, The slider includes: a slider body having raceway grooves disposed opposite the raceway grooves of the guide rail to form rolling paths for the rolling elements, and having return paths for the rolling elements; an end cap having a direction change passage connecting the return passage and the rolling passage, the raceway groove of the slider body has a first raceway surface on the central side of the rolling path and a second raceway surface on the end side of the rolling path, a chamfered portion having a tapered shape that gradually moves away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body is formed on the second raceway surface by cutting, At least the surface layers of the first raceway surface and the second raceway surface are heat treated so that the amount of retained austenite is 20% or more. A method for manufacturing a linear guide device comprising the steps of:

5. Before the heat treatment, a crowning portion having a tapered shape is formed between the first raceway surface and the chamfered portion by cutting or grinding, the crowning portion gradually moving away from the center line of the linear portion of the rolling path from the first raceway surface side toward the end face of the slider body.

5. The method for manufacturing a linear guide device according to claim 4.

6. The chamfered portion and the crowning portion are not subjected to finishing processing such as polishing to round the edges. The method for manufacturing a linear guide device according to claim 5 .

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