Linear motion guide device

Abstract

This linear motion guide device comprises: a guide rail; a slider disposed so as to move relative to the guide rail in a longitudinal direction; and a plurality of rolling elements disposed so as to be rollable along a rolling element rolling path formed between the guide rail and the slider. The slider includes: a slider body that has a raceway groove disposed to face a raceway groove of the guide rail and forming the rolling element rolling path for the rolling elements and that also has a return path for the rolling elements; and an end cap that has a direction change path connecting the return path and the rolling element rolling path. A scooping-up part for scooping up the rolling elements to the direction change path is formed at an end part of the direction change path on the guide rail side, and the inner surface of the scooping-up part is a part of a cylindrical surface. The cylindrical surface has a center line that intersects with the axis of the raceway groove of the slider body and that connects to the center line of the direction change path in a tangential direction.

Description

Linear motion guide device

[0001] The present invention relates to a linear motion guide device.

[0002] A linear motion guide device that linearly guides a guided object such as a workpiece while causing rolling elements such as rollers and balls to circulate infinitely inside is an important mechanical element that has a great influence on the motion accuracy of semiconductor manufacturing devices, ultra-precision machining machines, ultra-precision measuring instruments, etc.

[0003] The linear motion guide device includes a guide rail provided with a rail-side rolling element raceway groove, a slider-side rolling element raceway groove provided to face the rail-side rolling element raceway groove, and a slider body supported by the guide rail so as to be axially movable through the rolling of a plurality of rolling elements disposed in a rolling passage formed between the slider-side rolling element raceway groove and the rail-side rolling element raceway groove. The linear motion guide device further includes a rolling element return path provided in the slider body so as to be substantially parallel to the rolling passage, and a direction conversion path provided in end caps attached to both ends in the moving direction of the slider body to communicate the rolling passage and the rolling element return path.

[0004] In a linear motion guide device, when a rolling element rolling in the rolling passage enters the direction conversion path, there is a concern about fatigue failure of the collided part due to the rolling element repeatedly colliding with a wedge-shaped rolling element scooping-up portion. Particularly during high-speed operation, the collision of the rolling element against the rolling element scooping-up portion becomes prominent, and various countermeasures have been proposed.

[0005] As an example of a countermeasure, Patent Document 1 proposes a linear motion guide device in which an end cap is continuous with a direction conversion path so as to intersect the rolling passage, and has an introduction portion of the rolling passage including a first contact surface that guides a rolling element from one side portion of the rolling passage to the other side portion, and a second contact surface that is located on the opposite side of the first contact surface across the rolling passage and on which the rolling element rides over through the first contact surface.

[0006] International Publication No. 2013 / 065663

[0007] However, in the configuration shown in Patent Document 1, the first contact surface is positioned deep within the direction change path, which results in a large scooping angle (angle of intersection with the rolling passage) for the rolling element at the first contact surface. As a result, the collision force between the end cap and the rolling element becomes large, and there remains a concern about surface damage to the direction change path of the end cap and the rolling element.

[0008] The present invention has been made in view of the above problems, and aims to provide a linear motion guide device that can improve the durability of the end cap and ensure smooth movement of the rolling elements while mitigating impact forces.

[0009] The linear motion guide device of the present invention comprises a guide rail, a slider arranged to move relative to the guide rail in the longitudinal direction, and a plurality of rolling elements arranged to roll freely along a rolling element rolling path formed between the guide rail and the slider, wherein the slider comprises a slider body having a track groove arranged opposite to the track groove of the guide rail to form a rolling element rolling path for the rolling elements, and a return path for the rolling elements, and an end cap having a direction change path connecting the return path and the rolling element rolling path, wherein a scooping portion is formed at the end of the direction change path on the guide rail side for scooping the rolling elements into the direction change path, the inner surface of the scooping portion is part of a cylindrical surface, the center line of the cylindrical surface intersects with the axis of the track groove of the slider body and is connected tangentially to the center line of the direction change path.

[0010] According to the present invention, it is possible to provide a linear motion guide device that improves the durability of the end cap and ensures smooth movement of the rolling elements while mitigating impact forces.

[0011] Figure 1 is a perspective view showing a linear motion guide device according to the first embodiment of the present invention. Figure 2 is a front view of the end cap of the linear motion guide device of Figure 1, with the return guide attached, as seen from the slider body side along the longitudinal direction of the guide rail. Figure 3 is a cross-sectional view taken along line III-III of Figure 2, showing the end cap with the return guide attached attached to the slider body. Figure 4 is a view of the direction change path along the center line of the track groove, with the guide rail and slider combined. Figure 5 is a cross-sectional view similar to Figure 3, showing the end cap of Comparative Example 1 with the return guide attached attached to the slider body. Figure 6 is a cross-sectional view similar to Figure 4, relating to Comparative Example 1. Figure 7 is a cross-sectional view similar to Figure 3, showing the end cap of Comparative Example 2 with the return guide attached attached to the slider body. Figure 8 is a cross-sectional view similar to Figure 4, relating to Comparative Example 2. Figure 9 is a cross-sectional view similar to Figure 3, showing the end cap of the second embodiment with the return guide attached attached to the slider body. Figure 10 is a cross-sectional view taken along line X-X of Figure 7.

[0012] Embodiments of the present invention will be described in detail below with reference to the drawings. In this specification, terms indicating direction (up, down, etc.) refer to the respective directions in Figure 2 unless otherwise specified. Furthermore, "longitudinal direction" refers to the longitudinal direction of the guide rail or slider.

[0013] (First Embodiment) Figure 1 is a perspective view showing a linear motion guide device according to the first embodiment of the present invention. Figure 2 is a front view of the end cap 2B of the linear motion guide device of Figure 1, with the return guide 24 attached, as seen from the slider body 2A side along the longitudinal direction of the guide rail 1. Figure 3 is a cross-sectional view taken along line III-III of Figure 2, showing the end cap with the return guide attached attached to the slider body.

[0014] In Figure 1, a slider 2 with a roughly U-shaped cross-section is mounted along a guide rail 1 with a roughly rectangular cross-section that extends in a straight line, so as to be movable in the longitudinal direction of the guide rail 1. At the ridges where the left and right sides 1a, 1a in the width direction of the guide rail 1 intersect with the top surface 1b, track grooves 10A, 10A, which are concave grooves with a roughly quarter-circular arc cross-section, are formed along the longitudinal direction.

[0015] Furthermore, track grooves 10B, 10B, consisting of concave grooves with a roughly semicircular cross-section, are formed along the longitudinal direction at approximately the vertical center of both the left and right sides 1a, 1a in the width direction of the guide rail 1. In addition, a retainer groove 10Ba (wire groove) is formed at the bottom of the track grooves 10B, 10B, which accommodates a part of a retainer (not shown) and guides the retainer when the slider 2 moves, extending 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). The cross-sectional shape of the retainer groove 10Ba is, for example, roughly rectangular.

[0016] The cross-sectional shape of the raceway grooves 10A and 10B may be an arc shape consisting of a single arc, or it may be a roughly V-shape (Gothic arc-shaped groove) formed by combining two arcs with different centers of curvature.

[0017] The slider 2 comprises a slider body 2A and end caps 2B, 2B detachably attached to both ends (both ends in the longitudinal direction) of the slider body 2A. Furthermore, side seals 5, 5 are fitted to both ends of the slider 2 (the longitudinal outer end faces of each end cap 2B) to slide against the outer surface (upper surface 1b and side surfaces 1a, 1a) of the guide rail 1, sealing the portion of the gap opening between the guide rail 1 and the slider 2 that faces the longitudinal end face. An underseal (not shown) is fitted to the lower part of the slider 2 to seal the portion of the gap opening between the guide rail 1 and the slider 2 that faces the lower surface of the slider 2. These side seals 5, 5 and the underseal prevent foreign matter from entering the gap from the outside and prevent lubricant from leaking out of the gap.

[0018] As shown in Figure 2, the end cap 2B is made up of a pair of legs 22a and a body 22b connected together. On the slider body side of each leg 22a, there are arc grooves 221 and 222 that form the outer circumferential surface of the direction change path, and a recess 223 into which the return guide 24 is fitted.

[0019] The return guide 24 has a pair of inner arcuate surfaces 241 and 242 that form the inner circumferential surface of the direction change passage. When the return guide 24 is fitted into the recess 223 of the end cap 2B, the arcuate grooves 221 and 222 of the end cap 2B and the inner arcuate surfaces 241 and 242 of the return guide 24 face each other, forming semi-torus-shaped direction change passages 42, 42. An oil filler port 243 may be provided on the inner arcuate surfaces 241 and 242 of the return guide 24, and lubricant may be supplied to the direction change passage 42 through the oil filler port 243 (see Figure 3).

[0020] In the linear motion guide device of this embodiment, two pairs of four rows of rolling paths are formed by the track grooves 10A and 10B of the guide rails 1 and the track grooves 211 and 212 of the slider 2 (Figure 1), and each track and each return path 216 are connected by a direction change path 42 (Figure 3). In other words, two pairs of four rows of balls 3 are formed by the rolling paths, return paths 216 and direction change paths 42, and multiple balls (rolling elements) 3 are arranged within each circulation path. As a result, the slider 2 is supported by the balls 3 rolling under load within the two pairs of four rows of rolling paths, enabling it to move linearly along the guide rails 1.

[0021] The track grooves 211 and 212 of the slider 2 are connected to the arcuate grooves 221 and 222 of the end cap 2B, respectively. Also, as shown in Figure 3, the return path 216 has an annular recess 216a at its end. The direction change path 42, which consists of the arcuate grooves 221 and 222 of the end cap 2B and the inner arcuate surface 241 of the return guide 24, opens at the end of the cylindrical projection 42a that protrudes from the end cap 2B. By fitting the cylindrical projection 42a into the annular recess 216a, the return path 216 and the direction change path 42 are connected with their axes aligned.

[0022] The end cap 2B has a scooping section 25 formed at the track-side end of the arc groove 221 of the upper track, which scoops up the ball 3 from the track and guides it to each direction change path. The scooping section 25 of the arc groove 221 of the upper track will be described below, but the scooping section 25 of the arc groove 222 of the lower track is similar and will not be described.

[0023] The shape of the scooping section 25 will be explained in detail using Figures 3 and 4. Figure 4 is a view of the direction change path 42 along the axis O of the track groove 211, looking from bottom to top as shown in Figure 3, with the guide rail 1 and slider 2 combined. The inner circumferential surface of the track groove 211 constitutes a part of the cylindrical surface, and here the axis O is the center line of the cylindrical surface.

[0024] The inner surface 251 of the scooping portion 25 facing the return guide 24 has a maximum length L in the cross-section shown in Figure 3 and is connected along the tangential direction of the arc groove 221. The inner surface 251 constitutes a part of the cylindrical surface, and the boundary between the inner surface 251 and the arc groove 221 is smoothly connected. The inner diameter of the cylindrical surface formed by the inner surface 251 is equal to or slightly larger than the outer diameter of the ball 3.

[0025] When the axis of the cylindrical surface described above is Y, the axis (also called the center line) Y connects to the arc-shaped center line Z of the direction change path 42 and extends in the tangential direction. At this time, let α be the angle of intersection between the axis O of the track groove 211 and the center line Y.

[0026] The ball 3 is scooped up by the scooping section 25 from the rolling element track 41 formed by the track groove 10A (not shown in Figure 3) and track groove 211 of the guide rail 1, and guided to the direction change track 42 which consists of the arc groove 222 of the end cap 2B and the inner arc surface 242 of the return guide 24.

[0027] According to this embodiment, the center line Y of the cylindrical surface formed by the scooping portion 25 is continuously connected to the center line Z of the direction change path 42. This allows the intersection angle α to be set small, which reduces the collision force between the end cap 2B and the ball 3, further enhancing the effect of suppressing surface damage and fatigue of the end cap 2B and surface damage of the ball.

[0028] As shown in the cross-sectional view of Figure 3, the axis of the track groove 211 (center line of the rolling element's rolling path) O, the center line of the rolling element's return path 216, the center line Z of the direction change path 42, and the center line Y of the cylindrical surface formed by the scooping section 25 are all on the same plane, and in this embodiment, they are arranged in a plane parallel to the upper surface 1b of the guide rail 1.

[0029] Therefore, when viewed from the direction shown in Figure 4, the edge of the scooping portion 25 facing the raceway groove 10A is straight, and unlike Comparative Example 1 described later, the scooping portion 25 does not overlap with the raceway groove 10A. As a result, there is no need to provide a gap with the raceway groove 10A, and the position where the ball 3 rolling in the raceway groove 10A collides with the scooping portion 25 can be brought closer to the outer circumference of the ball 3. Therefore, the collision force between the end cap 2B and the ball 3 is reduced, which further enhances the effect of suppressing surface damage and fatigue of the end cap 2B and surface damage of the ball. Here, "not overlapping" means that, in Figure 4, when the widthwise boundary between the raceway groove 10A and the area outside the raceway groove 10A is connected by the dotted line DL, the scooping portion 25 does not extend beyond the dotted line DL into the raceway groove 10A side.

[0030] Furthermore, in this embodiment, the guide rail 1 has a chamfered portion 1c formed by removing the intersection between the track groove 10A and the upper surface 1b. The chamfered portion 1c extends longitudinally adjacent to the track groove 10A and has a shape and dimensions that do not interfere with the scooping portion 25 when the guide rail 1 is assembled to the slider 2. By forming the chamfered portion 1c, interference between the guide rail 1 and the scooping portion 25 can be avoided. As a result, the scooping portion 25 can be designed to be as thick as possible, and the strength of the end cap 2B can be increased.

[0031] In this embodiment, a scooping portion 25 formed at the end of the direction change path 42 of the end cap 2B has a cylindrical surface formed to guide the ball 3 to the direction change path 42. The center line Y of the cylindrical surface of the scooping portion 25 intersects the axis O of the raceway groove 211 of the slider body 2A at an angle α, and is continuously connected to the center line Z of the direction change path 42.

[0032] Since the center line Y of the cylindrical surface of the scooping section 25 intersects the axis O of the raceway groove 211 of the slider body 2A at an angle α, the ball 3 is smoothly scooped up along the surface formed by the axis O and the center line Y, and rolls along the inner surface 251 of the scooping section 25 in the tangential direction of the direction change path 42. As a result, the force that the scooping section 25 receives from the ball 3 can be mitigated, and combined with the improvement in the strength of the scooping section, fatigue and damage can be prevented.

[0033] Furthermore, because the centerline Y of the cylindrical surface of the scooping section 25 is continuously connected to the centerline Z of the direction change path 42 (extending tangentially to the centerline Z of the direction change path 42), the scooping angle (intersection angle α) can be set to be small. As a result, the collision force between the end cap 2B and the ball 3 during scooping is reduced, and fatigue of the end cap 2B can be suppressed. In addition, as is clear from Figure 4, the scooping section 25 has a cylindrical surface with a notch on the raceway groove 10A side. As a result, the ball 3 is in surface contact with this cylindrical surface, so the surface pressure acting on the scooping section is reduced, and fatigue and damage can be prevented. The effects of this embodiment will be explained below with reference to a comparative example.

[0034] (Comparative Example 1) Figure 5 is a cross-sectional view similar to Figure 3, showing the end cap 2B' of Comparative Example 1, with the return guide 24 attached, attached to the slider body 2A. Figure 6 is a cross-sectional view similar to Figure 4, of Comparative Example 1.

[0035] In Comparative Example 1, the inner surface of the tongue portion 25' of the end cap 2B' does not have a cylindrical shape, but is an extended surface of the arc groove 221. Furthermore, the scoop angle of the tongue portion 25' is β (>α). The other components (including the return guide 24 and the slider body 2A) are the same as in the first embodiment, so they are given the same reference numerals and their description is omitted.

[0036] In Comparative Example 1, as shown in Figure 6, a wedge-shaped tongue portion 25' is provided so as to overlap the raceway groove 10A of the guide rail 1. A gap is provided between this tongue portion 25' and the raceway groove 10A to account for assembly errors of the end cap 2B', etc. Therefore, as shown in Figure 5, the ball 3 rolling in the raceway groove 10A collides with the tongue portion 25' at a position slightly away from the contact point with the raceway groove 10A, that is, at the thicker portion of the ball 3, and is scooped up. As a result the scooping angle β becomes large, and problems such as chipping of the tongue portion 25' are likely to occur.

[0037] In contrast, according to this embodiment, since the scooping portion 25, which corresponds to the tongue portion 25', does not overlap the raceway groove 10A, there is no need to provide a gap with the raceway groove 10A as described in Comparative Example 1, and the position in which the ball 3 rolling in the raceway groove 10A collides with the scooping portion 25 can be brought closer to the outer circumference of the ball 3. Furthermore, by setting the intersection angle α to be small, the scooping portion 25 can smoothly scoop up the ball 3, thereby mitigating the impact force on the scooping portion 25 and reducing damage.

[0038] (Comparative Example 2) Figure 7 is a cross-sectional view similar to Figure 3, showing the end cap 2B'' of Comparative Example 2, with the return guide 24 attached, attached to the slider body 2A. Figure 8 is a cross-sectional view similar to Figure 4 of Comparative Example 2. Comparative Example 2 corresponds to, for example, the linear motion guide device described in International Patent No. 2013 / 065663.

[0039] In Comparative Example 2, the trackway groove 10A intersects with the direction change path 42 and is continuous with the trackway 42, providing a first contact surface CP1 that guides the ball 3 from one side to the other of the rolling element track 41, and a second contact surface CP2 located on the opposite side of the rolling element track 41 from the first contact surface CP1, onto which the rolling elements transfer. Also, the inner surface of the tongue portion 25" of the end cap 2B" does not have a cylindrical shape. The other components (including the return guide 24 and the slider body 2A) are the same as in the first embodiment, so they are given the same reference numerals and their description is omitted.

[0040] In Comparative Example 2, it is necessary to arrange the first contact surface CP1 at a position deep inside the direction conversion path 42. Although the contact portion is a thick portion and thus has high strength, the scooping angle γ becomes large, and as a result, the impact force of the ball 3 also becomes large. Therefore, there is concern about surface damage on the side of the direction conversion path 42 and the ball 3.

[0041] On the other hand, according to the present embodiment, different from Comparative Example 2, the scooping portion 25 arranged at the inlet of the direction conversion path 42 has, on its inner side, the cylindrical surface on which the ball 3 rolls. By adopting such a configuration, a scooping angle (intersection angle α) smaller than the scooping angle γ of Comparative Example 2 is realized, and the ball 3 can be smoothly scooped up by the scooping portion 25.

[0042] (Second Embodiment) FIG. 9 is a cross-sectional view similar to FIG. 3 showing a state where an end cap 2B according to the second embodiment with a return guide 24 attached is attached to a slider body 2A. FIG. 10 is a cross-sectional view taken along the line X-X of FIG. 9.

[0043] In the present embodiment, the cylindrical surface inside the scooping portion 25B is circular with a central angle θ of 90° or more in an arbitrary cross-section orthogonal to its center line. Since the other configurations (including the return guide 24 and the slider body 2A) are the same as those in the first embodiment, the same reference numerals are given and the description thereof is omitted. The central angle θ is preferably 180° or less.

[0044] According to the present embodiment, since the cylindrical surface inside the scooping portion 25B is circular with a central angle of 90° or more, when the outer peripheral surface of the ball 3 is scooped up in a state surrounded by the end cap 2B and the return guide 24, the ball 3 can be stably scooped up. As a result, it is possible to surely scoop up the ball 3 with the thick portion of the scooping portion 25B, and the effect of suppressing fatigue and breakage of the end cap 2B can be further enhanced. In particular, similar to the first embodiment, when the center line Y of the cylindrical surface is in an arrangement relationship existing in a plane parallel to the upper surface of the guide rail, there is an effect that it becomes easier to secure a central angle of 90° or more. Conversely, if the center line Y of the cylindrical surface is inclined with respect to the upper surface of the guide rail, it becomes difficult to secure a central angle of 90° or more.

[0045] In the above embodiment, the scooping portion is located outside the slider body 2A, but it may also be located opposite the raceway groove 10B of the slider body 2A. Furthermore, the outer wall of the direction change path 42 may be composed of multiple parts. For example, the arc groove may be made up of an end cap, and the scooping portion may be made up of a rolling element holder.

[0046] The present invention is not limited to the embodiments described above. It is also intended and within the scope of protection to be provided for the combination of each configuration of the embodiments, as well as for modifications and applications by those skilled in the art based on the description in the specification and well-known art.

[0047] This application is based on the Japanese Patent Application No. 2024-168721 filed on September 27, 2024, the contents of which are incorporated by reference within this application.

[0048] 1 Guide rail 2 Slider 2A Slider body 2B End cap 25, 25B Scoop-up section 3 Ball 10A, 10B Track groove 42 Direction change path

Claims

1. A linear motion guide device comprising: a guide rail; a slider arranged to move relative to the guide rail in the longitudinal direction; and a plurality of rolling elements arranged to roll freely along a rolling element path formed between the guide rail and the slider, wherein the slider comprises: a slider body having a track groove arranged opposite to the track groove of the guide rail to form a rolling element path for the rolling elements, and a return path for the rolling elements; and an end cap having a direction-changing path connecting the return path and the rolling element path, wherein a scooping portion is formed at the end of the direction-changing path on the guide rail side for scooping the rolling elements into the direction-changing path, the inner surface of the scooping portion is part of a cylindrical surface, and the center line of the cylindrical surface intersects with the axis of the track groove of the slider body and is connected tangentially to the center line of the direction-changing path.

2. The linear motion guide device according to claim 1, characterized in that, when viewed in the axial direction of the track groove of the slider body, the scooping portion does not overlap with the track groove of the guide rail.

3. The linear motion guide device according to claim 1, characterized in that, when viewed in the axial direction of the track groove of the slider body, a chamfered portion is formed on the guide rail adjacent to the track groove of the guide rail and facing the scooping portion.

4. The linear motion guide device according to claim 1, characterized in that, in any cross-section perpendicular to the center line of the inner surface of the scooping portion, the inner surface of the scooping portion is circular in shape of 90° or more.

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