Mounting hole cap and motion guide device

Abstract

To provide a cap for an attachment hole of a motion guide device which can inhibit occurrence of burrs and secure holding power and extraction power.SOLUTION: A cap 8 for an attachment hole of the invention includes a lid part 11 and a fitting part 12. The fitting part 12 includes first fitting parts 13 and second fitting parts 14 arranged in a circumferential direction. A slit 16 is formed between the first fitting part 13 and the second fitting part 14. On the first fitting part 13, a protrusion 17 which contacts with an inner surface of the attachment hole is formed. An outer diameter of the protrusion of the first fitting part 13 is larger than an outer diameter of the second fitting part 14.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a mounting hole cap for closing a mounting hole in a rail of a motion guide device, and a motion guide device equipped with this mounting hole cap. [Background technology]

[0002] A motion guide device is used to guide the linear motion (straight or curved motion) of a movable body such as a table. The motion guide device includes a rail attached to a base and a carriage mounted on the rail so as to be able to move linearly. The carriage is provided with a circulation path for circulating rolling elements that roll between the rail and the carriage.

[0003] Rails have mounting holes into which fastening members are inserted to fasten the rail to the base. If foreign matter such as dust and chips accumulates in these mounting holes, even the seal device installed on the carriage cannot remove the foreign matter. If foreign matter accumulates in the mounting holes and seeps into the carriage, it will interfere with the smooth rolling of the rolling elements. For this reason, the mounting holes in the rails are commonly covered with mounting hole caps.

[0004] Patent Document 1 discloses a conventional mounting hole cap with multiple protrusions on the periphery of a disk-shaped cap body. The cap is temporarily placed on the mounting hole and then driven into the mounting hole using a hammer or the like. The protrusions on the cap have interference. The interference of the protrusions allows the cap to be firmly fixed in the mounting hole.

[0005] Retention force and removal force are indicators of the force that secures a cap to a mounting hole. Retention force is the force required to sink the cap when it is pushed in from above after being hammered into the mounting hole of the rail. If the retention force is weak, the cap will sink in easily and foreign matter will accumulate on the top surface of the cap. Removal force is the force required to remove the cap from the mounting hole when the rail is inverted and the cap is pushed in from the bottom side of the rail. If the removal force is weak, the cap will easily come out of the mounting hole when the carriage runs on the rail. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-227838 Summary of the Invention [Problem to be solved by the invention]

[0007] In the mounting hole cap for a motion guide device described in Patent Document 1, an interference is provided on the protrusion of the cap to ensure retention and removal force. However, when the cap is hammered into the mounting hole, the protrusion is scraped off, causing burrs to form on the top surface of the rail. The burrs must be cut off and removed from the cap, and since there are many caps, this is a very time-consuming task. On the other hand, reducing the interference of the protrusion can reduce burr formation, but this in turn weakens the retention and removal force of the cap. As such, reducing burr formation and ensuring the retention and removal force of the cap are in a contradictory relationship, so the challenge with mounting hole caps is how to achieve both.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a cap for a mounting hole of a motion guide device that can suppress the occurrence of burrs and ensure holding force and removal force. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention One aspect of is a mounting hole cap for closing a mounting hole of a rail of a motion guide device, and comprises a lid portion and a fitting portion, the fitting portion comprises a first fitting portion and a second fitting portion arranged in a circumferential direction, and between the first fitting portion and the second fitting portion, Extending in the axial direction from the lower end of the fitting portion a slit is formed in the first fitting portion, and a protrusion is formed in the first fitting portion to come into contact with the inner surface of the mounting hole, and the outer diameter of the protrusion in the first fitting portion is larger than the outer diameter of the second fitting portion; Further, the amount of deflection of the lower end of the second fitting portion when a load toward the center of the mounting hole cap is applied to the lower end of the second fitting portion is smaller than the amount of deflection of the lower end of the first fitting portion when the same load toward the center of the mounting hole cap is applied to the lower end of the first fitting portion.This is a cap for the mounting hole. Another aspect of the present invention is a mounting hole cap for covering a mounting hole in a rail of a motion guide device, comprising a lid portion and a fitting portion, the fitting portion comprising a first fitting portion and a second fitting portion arranged in the circumferential direction, a slit formed between the first fitting portion and the second fitting portion, a protrusion formed on the first fitting portion that contacts the inner surface of the mounting hole, the outer diameter of the protrusion of the first fitting portion being larger than the outer diameter of the second fitting portion, and the outer surface of the second fitting portion being formed into a curved surface that is most bulged at the middle portion in the vertical direction. Yet another aspect of the present invention is a mounting hole cap for covering a mounting hole in a rail of a motion guide device, comprising a lid portion and a fitting portion, wherein the fitting portion comprises a first fitting portion and a second fitting portion arranged in the circumferential direction, a slit is formed between the first fitting portion and the second fitting portion, the first fitting portion has a protrusion that contacts the inner surface of the mounting hole, the outer diameter of the protrusion of the first fitting portion is larger than the outer diameter of the second fitting portion, a flange is formed on the upper part of the second fitting portion to cover the chamfered inner edge of the opening of the mounting hole, and the mounting hole cap does not have the flange on the outer surface of the upper part of the first fitting portion. Yet another aspect of the present invention is a mounting hole cap for covering a mounting hole in a rail of a motion guide device, comprising a lid portion and a fitting portion, the fitting portion comprising a first fitting portion and a second fitting portion arranged in the circumferential direction, a slit formed between the first fitting portion and the second fitting portion, the first fitting portion having a protrusion that contacts the inner surface of the mounting hole, the outer diameter of the protrusion of the first fitting portion being larger than the outer diameter of the second fitting portion, and the lid portion comprising a top plate portion and a reinforcing rib provided on the underside of the top plate portion and connected to the second fitting portion. [Effects of the Invention]

[0010] According to the present invention, the fitting portion of the mounting hole cap is composed of a first fitting portion and a second fitting portion separated by a slit, a protrusion is formed on the first fitting portion that contacts the inner surface of the mounting hole, and the outer diameter of the protrusion on the first fitting portion is made larger than the outer diameter of the second fitting portion, making it possible to suppress the occurrence of burrs while ensuring holding force and removal force. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. [Figure 2] FIG. [Figure 3] FIG. 2 is a perspective view of the top surface of the cap according to the first embodiment of the present invention. [Figure 4] FIG. 2 is a bottom perspective view of the cap of the present embodiment. [Figure 5] 5A and 5B are detailed views of the cap of this embodiment (FIG. 5A is a cross-sectional view taken along line XX in FIG. 5B, FIG. 5B is a bottom view, and FIG. 5C is a cross-sectional view taken along line YY in FIG. 5B). [Figure 6] FIG. 6 is an enlarged view of a portion VI in FIG. 5. [Figure 7] 10 is a cross-sectional view of the cap of the present embodiment temporarily placed in the mounting hole of the rail. FIG. [Figure 8] 10 is a cross-sectional view of the cap of the present embodiment with a backing plate attached thereto. FIG. [Figure 9] 4 is a cross-sectional view showing the dimensional relationship between a mounting hole of a rail and a cap of this embodiment. FIG. [Figure 10] 1 is a cross-sectional view of the cap of this embodiment in the state where it is driven into the mounting hole of the rail. FIG. [Figure 11] FIG. 11 is an enlarged view of the X portion of FIG. [Figure 12]FIG. 10 is a bottom perspective view of a cap according to a second embodiment of the present invention. [Figure 13] FIG. 10 is a bottom perspective view of a cap according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a cap for a mounting hole of a motion guide device (hereinafter simply referred to as a cap) according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the cap of the present invention can be embodied in various forms and is not limited to the embodiments described in the specification. The present embodiment is provided with the intention that those skilled in the art will be able to fully understand the scope of the invention by fully disclosing the specification. (First embodiment)

[0013] First, the configuration of the motion guide device will be described. Fig. 1 shows a perspective view of the motion guide device, and Fig. 2 shows a cross-sectional view of the motion guide device. The motion guide device includes a rail 1 and a carriage 2 that is attached to the rail 1 via a plurality of rolling elements 3 such as balls or rollers so as to be able to move linearly (linearly or curvedly) in the length direction.

[0014] As shown in FIG. 1, rail 1 extends in a straight or curved shape. Rail 1 is formed with a rolling element rolling section 1a along which rolling elements 3 roll. Carriage 2 is formed with a rolling element rolling section 2a that faces rolling element rolling section 1a of rail 1. Rolling elements 3 are interposed between rolling element rolling section 1a of rail 1 and rolling element rolling section 2a of carriage 2 so that they can roll. Carriage 2 is provided with a circulation path that circulates rolling elements 3. Reference numeral 6 denotes a sealing device that removes foreign matter adhering to rail 1.

[0015] For ease of explanation, the configuration of the motion guide device will be described below using the directions when rail 1 is attached to a horizontal surface and viewed from the longitudinal direction of rail 1, i.e., the up-down, left-right, and front-rear directions in Figures 1 and 2. Of course, the arrangement of the motion guide device is not limited to this, and rail 1 may be attached to a vertical surface or the motion guide device may be turned upside down.

[0016] A plurality of mounting holes 5 are formed at regular intervals in the longitudinal direction on the upper surface of the rail 1. Bolts 4, which are fastening members for fastening the rail 1 to a base 7, are inserted into the mounting holes 5.

[0017] As shown in Figure 2, the mounting hole 5 has a counterbore portion 5a into which the head 4a of the bolt 4 is seated, and an insertion hole 5b into which the threaded portion 4b of the bolt 4 is inserted. A chamfer 5c (see also Figure 9) is provided on the inner peripheral edge of the opening of the counterbore portion 5a. The height of the counterbore portion 5a is greater than the height of the head 4a of the bolt 4 so that the bolt 4 is completely embedded in the mounting hole 5.

[0018] 1 and 2 show a state in which a bolt 4 is passed through a mounting hole 5 of a rail 1 and fastened to a base 7. The mounting hole 5 is then closed with a cap 8.

[0019] Fig. 3 shows a top perspective view of the cap 8 of the first embodiment of the present invention, Fig. 4 shows a bottom perspective view, and Fig. 5 shows detailed views of the cap 8, including a cross-sectional view and a bottom view.

[0020] As shown in Fig. 3, the cap 8 includes a lid portion 11 and a fitting portion 12. The fitting portion 12 is formed integrally with the lid portion 11. The top surface of the cap 8 is formed on the lid portion 11. The side surface of the cap 8 is formed on the fitting portion 12. The cap 8 is manufactured by, for example, injection molding of resin.

[0021] As shown in FIG. 4, the lid 11 includes a substantially disk-shaped top plate 11a and reinforcing ribs 11b provided on the underside of the top plate 11a. The reinforcing ribs 11b include an annular rib 11b1 formed in an annular shape around the center of the top plate 11a, and radial ribs 11b2 extending radially from the annular rib 11b1. The radial ribs 11b2 are connected to both ends of the second fitting portion 14 in the circumferential direction. The annular rib 11b1 reinforces the top plate 11a, and the radial ribs 11b2 reinforce the second fitting portion 14. The annular rib 11b1 and the radial ribs 11b2 extend from the underside of the top plate 11a to the underside of the fitting portion 12 (see FIG. 5(a)).

[0022] As shown in FIG. 3, the fitting portion 12 extends downward from the outer periphery of the cover portion 11. The fitting portion 12 is approximately cylindrical. The fitting portion 12 includes a plurality of first fitting portions 13 and a plurality of second fitting portions 14 arranged in the circumferential direction. The first fitting portions 13 and the second fitting portions 14 are arranged alternately in the circumferential direction. The second fitting portions 14 are arranged diagonally opposite the first fitting portions 13. Note that at least one first fitting portion 13 and one second fitting portion 14 are required.

[0023] A slit 16 is formed between the first fitting portion 13 and the second fitting portion 14. The first fitting portion 13 and the second fitting portion 14 are defined by the slit 16. The slit 16 extends from the lower end of the fitting portion 12 in the axial direction to the top plate portion 11a.

[0024] The first fitting portion 13 is formed with a protrusion 17 that contacts the inner surface of the mounting hole 5 of the rail 1. The protrusion 17 extends in the circumferential direction. As shown in FIG. 5( a), the outer surface of the protrusion 17 is formed with a cylindrical first parallel portion 17a that is approximately parallel to the inner surface of the mounting hole 5. Below the first parallel portion 17a of the protrusion 17, a guide slope 17b is formed that guides the protrusion 17 as it enters the mounting hole 5. Below the protrusion 17 of the first fitting portion 13, a cylindrical second parallel portion 18 that is approximately parallel to the inner surface of the mounting hole 5 is formed. At the lower end of the first fitting portion 13, a guide slope 19 is formed that guides the first fitting portion 13 as it enters the mounting hole 5. At the upper part of the protrusion 17 of the first fitting portion 13, a cylindrical third parallel portion 25 that is approximately parallel to the inner surface of the mounting hole 5 is formed.

[0025] 3, a flange 24 is formed on the upper part of the second fitting portion 14 to cover the chamfer 5c on the inner peripheral edge of the opening of the mounting hole 5. This flange 24 is formed only on the upper part of the second fitting portion 14, and is not formed on the upper part of the first fitting portion 13. In other words, the flange 24 is formed discontinuously around the periphery of the cap 8.

[0026] As shown in FIGS. 5(a) and 5(b), the outer diameter Φ1 of the protrusion 17 of the first fitting portion 13 is larger than the outer diameter Φc of the second fitting portion 14, i.e., the outer diameter Φc of the outer surface 14a of the second fitting portion 14 below the flange 24. The outer surface 14a of the second fitting portion 14 below the flange 24 is formed in a curved shape resembling a drum, with the central portion in the vertical direction being the most bulging. As shown in FIG. 6, the outer surface 14a of the second fitting portion 14 is curved in vertical cross section. The outer diameter Φc of the central portion of the outer surface 14a of the second fitting portion 14 is larger than the outer diameter Φa of the upper portion and the outer diameter Φb of the lower portion. The maximum diameter Φc of the outer surface 14a is the outer diameter Φc of the second fitting portion 14.

[0027] The second fitting portion 14 is formed to be less likely to bend toward the inside of the cap 8 than the first fitting portion 13. As shown in Fig. 5(a), the amount of bending of the lower end of the second fitting portion 14 when a load P toward the center of the cap 8 is applied to the lower end of the second fitting portion 14 is smaller than the amount of bending of the lower end of the first fitting portion 13 when a load P toward the center of the cap 8 is applied to the lower end of the first fitting portion 13.

[0028] 5(b), arc-shaped grooves 21a and 21b that make the first fitting portion 13 more easily deflectable than the second fitting portion 14 are formed on the underside of the top plate portion 11a of the lid portion 11 along the first fitting portion 13. A beam 22 that suppresses deformation of the top plate portion 11a is formed between the arc-shaped grooves 21a and 21b.

[0029] The process of hammering the cap 8 into the mounting hole 5 will be described below. First, as shown in FIG. 7, the cap 8 is temporarily placed in the mounting hole 5. At this time, the protrusion 17 of the first fitting portion 13 of the cap 8 catches on the chamfer 5c of the mounting hole 5. The amount H1 that the cap 8 enters into the mounting hole 5, i.e., the amount H1 that the cap 8 enters below the chamfer 5c, is 25% or more, and preferably 30% or more, of the thickness (H) of the cap 8 in the vertical direction.

[0030] When the cap 8 is temporarily placed in the mounting hole 5, the second parallel portion 18 of the first fitting portion 13 of the cap 8 enters the mounting hole 5, and the outer surface 14a of the second fitting portion 14 of the cap 8 comes into contact with the mounting hole 5. This, combined with the fact that H1 is 25%, prevents the temporarily placed cap 8 from tilting, improving the stability of the cap 8.

[0031] Next, as shown in Figure 8, backing plate 23 is placed on cap 8 and struck with a hammer. Figure 9 shows the dimensional relationship between cap 8 and mounting hole 5 before deflection deformation. When cap 8 is hammered into mounting hole 5, protrusion 17 of first fitting portion 13 is press-fitted into mounting hole 5, and outer surface 14a of second fitting portion 14 is press-fitted into mounting hole 5. Cap 8 is press-fitted into mounting hole 5 with interferences δ1 and δ2. This ensures sufficient holding force and removal force.

[0032] Here, the outer diameter Φ1 of the protrusion 17 of the first fitting portion 13 is larger than the outer diameter Φc of the outer surface 14a of the second fitting portion 14. Therefore, the interference δ1 of the first fitting portion 13 is larger than the interference δ2 of the second fitting portion 14. The first fitting portion 13 is press-fitted into the mounting hole 5 with an interference δ1 that is larger than that of the second fitting portion 14. Depending on the dimensional tolerance of the mounting hole 5, a slight gap may be present between the outer surface 14a of the second fitting portion 14 and the inner surface of the mounting hole 5; it is sufficient that there is at least an interference δ1 between the first fitting portion 13 and the mounting hole 5.

[0033] 9, when the cap 8 is hammered into the mounting hole 5, the flange 24 of the second fitting portion 14 rests on the chamfer 5c of the mounting hole 5. Therefore, the shear force of the flange 24 can ensure a holding force.

[0034] As shown in FIG. 10, when the cap 8 is press-fitted into the mounting hole 5, the protrusion 17 of the first fitting portion 13 comes into contact with the inner surface of the mounting hole 5, causing the first fitting portion 13 to bend. This prevents burrs from forming on the first fitting portion 13. The second fitting portion 14 is press-fitted into the mounting hole 5 with a smaller interference δ2 than the first fitting portion 13. Therefore, as shown in the enlarged view of FIG. 11, the area 20 of the second fitting portion 14 that will become a burr (the area indicated by the crossed lines in the figure) is small, and almost no burrs are generated. Even if burrs are generated, the outer surface 14a of the second fitting portion 14 is curved like a drum, so the burrs 23 are trapped between the flange 24 of the cap 8 and the chamfer 5c of the mounting hole 5. This prevents the burrs 23 from protruding onto the top surface of the rail 1.

[0035] The configuration and driving process of the cap 8 of this embodiment have been described above. The cap 8 of this embodiment has the following advantages.

[0036] The fitting portion 12 of the cap 8 is composed of a first fitting portion 13 and a second fitting portion 14 separated by a slit 16, and a protrusion 17 that contacts the inner surface of the mounting hole 5 is formed on the first fitting portion 13, and the outer diameter Φ1 of the protrusion 17 is made larger than the outer diameter Φc of the second fitting portion 14, so that it is possible to suppress the occurrence of burrs while ensuring holding force and removal force.

[0037] A flange 24 is formed on the upper part of the second fitting portion 14 to cover the chamfer 5c of the opening of the mounting hole 5, thereby ensuring a holding force.

[0038] The outer surface 14a of the second fitting portion 14 is formed into a curved surface with the middle portion in the vertical direction being the most bulged, thereby ensuring the holding force and removal force of the second fitting portion 14 and suppressing the generation of burrs at the second fitting portion 14.

[0039] Since no flange 24 is formed on the top of the first fitting portion 13, it is possible to prevent undercuts from occurring between the flange 24 and the protrusion 17, and the cap 8 can be easily molded from resin. Furthermore, even if burrs occur on the protrusion 17 of the first fitting portion 13, the burrs can be contained in the space s (see FIG. 10) above the protrusion 17, or can be transferred to the inside of the cap 8 via the slit 16. Therefore, it is possible to prevent the burrs from escaping to the outside. The space s is formed to a size that allows the burrs to remain in the space s without escaping to the outside.

[0040] Since the cover portion 11 is provided with the reinforcing rib 11b connected to the second fitting portion 14, the second fitting portion 14 can be made less likely to bend.

[0041] Since the amount of insertion (H1) when the cap 8 is temporarily placed in the mounting hole 5 is 25% or more of the thickness (H) of the cap 8 in the vertical direction, the cap 8 can be placed firmly. (Second embodiment)

[0042] 12 shows a bottom perspective view of a cap 31 according to a second embodiment of the present invention. This cap 31 also includes a lid portion 11 and a fitting portion 12. Reference numeral 11a denotes a top plate portion of the lid portion 11, 11b1 and 11b2 denote reinforcing ribs of the lid portion 11, 13 denotes a first fitting portion, 17 denotes a protrusion of the first fitting portion, and 14 denotes a second fitting portion. These components are substantially the same as those of the cap 8 according to the first embodiment, and therefore the same reference numerals are used and their description will be omitted.

[0043] In the cap 8 of the first embodiment, the beams 22 (see FIG. 5(b)) that suppress deformation of the top plate portion 11a of the lid portion 11 are formed only between the grooves 21a and 21b, but in the cap 31 of the second embodiment, the beams 32 are not only formed between the grooves 21a and 21b, but also extend radially from the annular rib 11b1 to the first fitting portion 13. When it is desired to further suppress deformation of the top plate portion 11a, the beams 32 may be formed in this manner. However, if the beams 32 are formed over the entire underside of the top plate portion 11a, the first fitting portion 13 becomes difficult to flex and there is a risk of burrs being generated, so it is desirable to form the beams 32 by thickening only a portion of the underside of the top plate portion 11a. (Third embodiment)

[0044] 13 shows a bottom perspective view of a cap 41 according to a third embodiment of the present invention. This cap 41 also includes a lid portion 11 and a fitting portion 12. The configurations of the top plate portion 11a of the lid portion 11, the reinforcing ribs 11b1 and 11b2, the first fitting portion 13, the protrusion 17, and the second fitting portion 14 are substantially the same as those of the cap 8 according to the first embodiment, and therefore the same reference numerals are used and a description thereof will be omitted.

[0045] In the cap 8 of the first embodiment, grooves 21a and 21b are formed in the underside of the top plate 11a to facilitate bending of the first fitting portion 13. On the other hand, in the cap 41 of the third embodiment, no grooves are formed, and the underside of the top plate 11a is flat. If the dimensions of the mounting hole 5 are large, the vertical length of the first fitting portion 13 also increases, making it easier for the first fitting portion 13 to bend. Therefore, the first fitting portion 13 can be bent even without forming grooves 21a and 21b in the underside of the top plate 11a.

[0046] The present invention is not limited to the above-described embodiment, and can be embodied in other embodiments without departing from the spirit of the present invention.

[0047] For example, in the above embodiment, the protrusion formed on the first fitting portion extends in the circumferential direction, but it may extend in the axial direction.Furthermore, the protrusion may be composed of one or more projections.

[0048] In the above embodiment, no flange is provided on the top of the first fitting portion, but a flange may be provided on the top of the first fitting portion. [Explanation of symbols]

[0049] 1...rail, 2...carriage, 4...bolt (fastening member), 5...mounting hole, 8...mounting hole cap, 11...lid portion, 11a...top plate portion, 11b...reinforcing rib, 12...fitting portion, 13...first fitting portion, 14...second fitting portion, 14a...outer surface of second fitting portion, 16...slit, 17...projection portion, 24...flange, 31...cap, 41...cap, Φ1...outer diameter of projection of first fitting portion, Φc...outer diameter of second fitting portion

Claims

1. A mounting hole cap for closing a mounting hole of a rail of a motion guide device, The device includes a lid portion and a fitting portion, the fitting portion includes a first fitting portion and a second fitting portion arranged in a circumferential direction, A slit is formed between the first fitting portion and the second fitting portion, extending in the axial direction from a lower end of the fitting portion, The first fitting portion is formed with a protrusion that contacts the inner surface of the mounting hole, an outer diameter of the protrusion of the first fitting portion is larger than an outer diameter of the second fitting portion; A mounting hole cap in which the amount of deflection of the lower end of the second fitting portion when a load toward the center of the mounting hole cap is applied to the lower end of the second fitting portion is smaller than the amount of deflection of the lower end of the first fitting portion when the same load toward the center of the mounting hole cap is applied to the lower end of the first fitting portion.

2. The cap for a mounting hole according to claim 1 , wherein a flange is formed on an upper portion of the second fitting portion to cover the chamfered inner periphery of the opening of the mounting hole.

3. A mounting hole cap for closing a mounting hole of a rail of a motion guide device, The device includes a lid portion and a fitting portion, the fitting portion includes a first fitting portion and a second fitting portion arranged in a circumferential direction, a slit is formed between the first fitting portion and the second fitting portion, The first fitting portion is formed with a protrusion that contacts the inner surface of the mounting hole, an outer diameter of the protrusion of the first fitting portion is larger than an outer diameter of the second fitting portion; The outer surface of the second fitting portion is formed into a curved surface that is most convex at the middle portion in the vertical direction.

4. A mounting hole cap for closing a mounting hole of a rail of a motion guide device, The device includes a lid portion and a fitting portion, the fitting portion includes a first fitting portion and a second fitting portion arranged in a circumferential direction, a slit is formed between the first fitting portion and the second fitting portion, The first fitting portion is formed with a protrusion that contacts the inner surface of the mounting hole, an outer diameter of the protrusion of the first fitting portion is larger than an outer diameter of the second fitting portion; a flange is formed on an upper portion of the second fitting portion to cover the chamfered inner peripheral edge of the opening of the mounting hole; A mounting hole cap having no flange formed on an outer surface of an upper portion of the first fitting portion.

5. A mounting hole cap for closing a mounting hole of a rail of a motion guide device, The device includes a lid portion and a fitting portion, the fitting portion includes a first fitting portion and a second fitting portion arranged in a circumferential direction, a slit is formed between the first fitting portion and the second fitting portion, The first fitting portion is formed with a protrusion that contacts the inner surface of the mounting hole, an outer diameter of the protrusion of the first fitting portion is larger than an outer diameter of the second fitting portion; The lid portion is a mounting hole cap comprising a top plate portion and a reinforcing rib provided on the underside of the top plate portion and connected to the second fitting portion.

6. A mounting hole cap according to any one of claims 1 to 5, characterized in that when the mounting hole cap is temporarily placed in the mounting hole, the amount (H1) that the mounting hole cap penetrates into the mounting hole is 25% or more of the vertical thickness (H) of the mounting hole cap.

7. The mounting hole cap according to any one of claims 1 to 5, Rails and a carriage attached to the rail so as to be relatively movable.

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