Motion guide device

Abstract

To provide a motion guide device capable of maintaining arrangement of at least two rows of balls using a plurality of separate retainers, and capable of suppressing elastic deformation of the separate retainers on a turn path.SOLUTION: In a motion guide device in which at least two rows of balls 6 are arranged in a circulation path, a plurality of separate retainers 21a, 21b are provided to rotatably hold the at least two rows of balls 6. One separate retainer 21a holds a total of three balls 6: one ball 6a in one row L1; and two balls 6b in the other row L2. The other separate retainer 21b holds a total of three balls 6: one ball 6b in the other row L2; and two balls 6a in the one row L1.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a motion guide device in which at least two rows of balls are arranged in a circulating path. [Background technology]

[0002] There is known a motion guide device that guides the linear motion of a table or the like relative to a base. The motion guide device includes a rail and a carriage that moves relative to the rail. A plurality of balls are interposed between the rail and the carriage so as to be capable of rolling motion. The balls circulate in a circulation path that includes a rolling path between the rail and the carriage, a return path for the carriage, and a turning path for the carriage.

[0003] A motion guide device has been proposed in which at least two rows of balls are arranged in a circulation path (see Patent Document 1). This motion guide device can reduce carriage waving (vibration of the carriage as the balls pass by), and can provide high-precision guidance.

[0004] The method of retaining at least two rows of balls in the circulation path includes the linked cage method. In the linked cage method, all of the balls in the at least two rows are held in series by the linked cage. On the other hand, in the full ball method, only at least two rows of balls are arranged in the circulation path, and no linked cage is arranged. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2014-055670 A Summary of the Invention [Problem to be solved by the invention]

[0006] By adopting the linked retainer system, it is possible to maintain an arrangement of at least two rows of balls in the circulation path. However, the linked retainer system has the problem that the linked retainer is forced to undergo elastic deformation in the turning path. For this reason, it is necessary to use a material for the linked retainer that is durable against repeated elastic deformation.

[0007] The full-ball system has the problem that, in order to maintain an arrangement of at least two rows of balls, the design values ​​and tolerances of the clearance between the circulation path and the balls are severely restricted.

[0008] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a motion guide device that can maintain an arrangement of at least two rows of balls using multiple separate retainers and can suppress elastic deformation of the separate retainers on turning paths. [Means for solving the problem]

[0009] In order to solve the above problems, one aspect of the present invention is a motion guide device comprising a rail, a carriage capable of moving relative to the rail, and at least two rows of balls arranged in a circulation path including a rolling path between the rail and the carriage, a return path for the carriage, and a turning path for the carriage, wherein a plurality of separate retainers are provided to rotatably hold the at least two rows of balls, one separate retainer holding one ball from one row and two balls from the other row, for a total of three balls, and the other separate retainer holding one ball from the other row and two balls from the one row, for a total of three balls. Effect of the Invention

[0010] According to the present invention, a plurality of separate retainers are provided to rotatably hold at least two rows of balls, so that an arrangement of at least two rows of balls can be maintained. In addition, the present invention utilizes the principle that a plane is determined by three points (the centers of three balls), and since the separate retainer holds a total of three balls, elastic deformation of the separate retainer on a turning path can be suppressed. In contrast, if the separate retainer holds four or more balls, it is difficult to arrange the centers of the four or more balls on a plane on a turning path, so the separate retainer becomes more susceptible to elastic deformation. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view (including a partial cross-sectional view) of a motion guide device according to a first embodiment of the present invention. [Diagram 2] 2 is a front view of the motion guide device with the front end plate removed. FIG. [Diagram 3] FIG. [Figure 4] FIG. [Diagram 5] FIG. 2 is a perspective view of a plurality of separate retainers according to the embodiment. [Figure 6] FIG. 6(a) is a plan view of a plurality of separate retainers of this embodiment, FIG. 6(b) is a side view, and FIG. 6(c) is a front view. [Figure 7] FIG. 7(a) is a perspective view of the separate retainer of this embodiment, and FIG. 7(b) is a perspective view of the state with the balls removed. [Figure 8] FIG. 8(a) is a plan view of the separate retainer of this embodiment, FIG. 8(b) is a side view, and FIG. 8(c) is a front view. [Figure 9] FIG. 9(a) is a plan view of the separate retainer of this embodiment with the balls removed, FIG. 9(b) is a side view, and FIG. 9(c) is a front view. [Figure 10] 2 is a perspective view of a turning path of the motion guide device of the present embodiment. FIG. [Figure 11] 2 is a plan view of a turning path of the motion guide device of the present embodiment. FIG. [Figure 12] FIG. 12(a) is a front view of a turning path of the motion guide device of this embodiment, and FIG. 12(b) is a side view. [Figure 13] FIG. 13(a) is a perspective view of a separate retainer according to a second embodiment of the present invention, and FIG. 13(b) is a perspective view of the state in which the balls have been removed. [Figure 14] FIG. 14(a) is a bottom view of a separate retainer according to a second embodiment of the present invention, FIG. 14(b) is a side view, and FIG. 14(c) is a front view. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, a motion guide device according to an embodiment of the present invention will be described with reference to the accompanying drawings. However, the motion guide device according to the present invention can be embodied in various forms and is not limited to the embodiments described in this specification. The present embodiment is provided with the intention of enabling a person skilled in the art to fully understand the invention by fully disclosing the specification. (First embodiment)

[0013] 1 and 2 show a motion guide device according to a first embodiment of the present invention. FIG. 1 shows a perspective view (including a partial cross-sectional view) of the motion guide device. FIG. 2 shows a front view of the motion guide device with the end plate removed. For ease of explanation, the configuration of the motion guide device will be explained below using the directions when the motion guide device arranged on a horizontal plane is viewed from the relative movement direction of the carriage 2, that is, the up / down, left / right, and front / back directions in FIG. 1 and FIG. 2. Of course, the arrangement of the motion guide device is not limited to this.

[0014] As shown in FIG. 1, the motion guide device includes a rail 1 and a carriage 2. The rail 1 is attached to a base or the like (not shown). The carriage 2 is attached to a table or the like (not shown). The carriage 2 is capable of linear motion along the rail 1. Two circulation paths 7, one above the other and one below the other, are provided on the left and right sides of the carriage 2. FIG. 1 shows the two circulation paths 7 on the right side of the carriage 2. Each circulation path 7 includes a rolling path C1 between the rolling part 12 of the rail 1 and the rolling part 13 of the carriage 2, and a return path C2 and a turn path C3 provided on the carriage 2. Two rows of balls 6 are arranged in a staggered pattern on the circulation path 7.

[0015] As shown in Figure 1, two rolling parts 12, one above the other, are formed on the left and right protrusions 11 of the rail 1. Each rolling part 12 has two rows of rolling grooves 1a in which two rows of balls 6 roll. Each rolling groove 1a is, for example, a circular arc groove whose cross section is a single arc. An attachment hole 1b is formed on the top surface of the rail 1 for attaching the rail 1 to a base or the like.

[0016] The carriage 2 includes a carriage body 3, an inner plate 4 attached to both end surfaces of the carriage body 3, and an end plate 5 attached to both end surfaces of the carriage body 3 so as to cover the inner plate 4.

[0017] As shown in Figure 2, the carriage body 3 has a central portion 3a facing the upper surface of the rail 1, and left and right sleeve portions 3b facing the side surfaces of the rail 1. A rolling portion 13 (see Figure 1) facing the rolling portion 12 of the rail 1 is formed on the sleeve portions 3b of the carriage body 3. The rolling portion 13 has two rows of rolling grooves 3c in which two rows of balls 6 roll. Each rolling groove 3c is, for example, a circular arc groove having a cross section shaped like a single circular arc. An attachment screw 10 is formed on the upper surface of the carriage body 3 for attaching the carriage 2 to a base or the like.

[0018] A linear rolling path C1 is formed between the rolling part 13 of the carriage body 3 and the rolling part 12 of the rail 1. The rolling path C1 has two rows of rolling parts on which two rows of balls 6 roll. The right-angled cross-sectional shape of the rolling path C1 is gourd-shaped and is based on two imaginary circles that partially overlap each other. In the rolling path C1, the two rows of balls 6 receive a load. The symbol θ in FIG. 2 is a contact angle that indicates the direction in which the two rows of balls 6 receive a load. The contact angle θ is set to, for example, 30 to 60°.

[0019] As shown in FIG. 1, through holes 14 are formed parallel to the rolling path C1 at the top and bottom of the left and right sleeves 3b of the carriage body 3. A pair of half pipes 8, 9 constituting the return path C2 are inserted into the through holes 14. The return path C2 is linear and parallel to the rolling path C1. The return path C2 has two rows of return sections in which two rows of balls 6 are arranged. The rectangular cross-sectional shape of the return path C2 is gourd-shaped and is based on two imaginary circles that partially overlap each other.

[0020] As shown in Fig. 2, in the motion guide device of this embodiment, the return path C2 is positioned offset from the direction of the contact angle lines N1, N2. The upper return path C2 is positioned below the contact angle line N1 of the upper ball 6. The lower return path C2 is positioned above the contact angle line N2 of the lower ball 6. This allows the carriage 2 to be made more compact. Note that the return path C2 may also be positioned in the direction of the contact angle lines N1, N2.

[0021] Between the inner plate 4 and the end plate 5, a substantially U-shaped turning path C3 is formed. As shown in FIG. 3, the inner plate 4 has a central portion 4a facing the upper surface of the rail 1, and a pair of left and right sleeve portions 4b facing the side surfaces of the rail 1. Above and below the left and right sleeve portions 4b of the inner plate 4, substantially semi-cylindrical R piece portions 31 are formed. Two rows of track surfaces 31a are formed on the outer surface of the R piece portion 31. Each track surface 31a has an arc-shaped cross section. Reference numeral 37 denotes a mounting hole for mounting the inner plate 4 to the carriage body 3.

[0022] As shown in Fig. 4, the end plate 5 also has a central portion 5a facing the upper surface of the rail 1, and a pair of left and right sleeve portions 5b facing the side surfaces of the rail 1. Recesses 32 into which the R piece portions 31 fit are formed above and below the left and right sleeve portions 5b of the end plate 5. Two rows of track surfaces 32a are formed on the inner surface of the recess 32. Each track surface 32a has an arc-shaped cross section. Reference numeral 38 denotes a mounting hole for mounting the end plate 5 to the carriage body 3.

[0023] The end plate 5 and the inner plate 4 are attached to the carriage body 3 by screws. When the end plate 5 and the inner plate 4 are combined, a substantially U-shaped turning path C3 (see FIG. 1) is formed between the recess 32 of the end plate 5 and the R piece portion 31 of the inner plate 4. The turning path C3 has two rows of turning portions in which two rows of balls 6 are arranged. The total length of the turning portions in one row is equal to the total length of the turning portions in the other row. The perpendicular cross-sectional shape of the turning path C3 is gourd-shaped, and is based on two imaginary circles that partially overlap each other.

[0024] As shown in Fig. 2, a guide groove 7a that guides the separate retainer 21 is formed in the circulation path 7. However, in this embodiment, the separate retainer 21 is configured so as to enter the guide groove 7a but not come into contact with it, as will be described later. In the rolling path C1, the guide groove 7a is formed between the carriage body 3 and the rail 1. In the return path C2, the guide groove 7a is formed between a pair of half pipes 8, 9. In the turning path C3, the guide groove is formed between the inner plate 4 and the end plate 5.

[0025] As shown in Figs. 5 and 6, two rows of balls 6 are arranged in a staggered manner in the circulation path 7. The two rows of balls 6 are rotatably held by a plurality of separate retainers 21 (separate retainers 21a and 21b). One separate retainer 21a holds one ball 6a in one row L1 and two balls 6b in the other row L2, totaling three balls 6a and 6b. The other separate retainer 21b adjacent to the separate retainer 21a holds two balls 6a in one row L1 and one ball 6b in the other row L2, totaling three balls 6a and 6b. The separate retainers 21a and 21b are arranged alternately in the circulation path 7. The separate retainers 21a and 21b have the same shape. Separate retainer 21b is obtained by rotating separate retainer 21a 180 degrees in a plane. In the following, when there is no need to distinguish between separate retainer 21a and separate retainer 21b, they will simply be referred to as separate retainer 21. Similarly, when there is no need to distinguish between ball 6a and ball 6b, they will simply be referred to as ball 6.

[0026] As shown in FIG. 6(a), the pitch of the balls 6a in one row L1 is a constant P. The pitch of the balls 6b in the other row L2 is a constant P. The balls 6a in one row L1 and the balls 6b in the other row L2 are shifted by P / 2 in the moving direction. The triangle connecting the centers of the three balls 6 held by the separate retainer 21 is an equilateral triangle. As shown in FIG. 6(c), when viewed from the moving direction of the separate retainer 21 (when viewed from the front of the separate retainer 21), the balls 6a in one row L1 and the balls 6b in the other row L2 overlap. This allows the two rows of balls 6 to be compactly and ideally arranged. The balls 6 in the two rows may be arranged in the same phase in the circulation path 7, or if the dimensions of the circulation path 7 allow, the balls 6a in one row L1 and the balls 6b in the other row L2 do not need to overlap.

[0027] The positions of the two rows of balls 6 are determined by the rolling path C1 between the rolling part 12 of the rail 1 and the rolling part 13 of the carriage body 3, and are also determined by the turning path C3 of the carriage 2 and the return path C2 of the carriage 2. The position of the separate retainer 21 is determined by the three balls 6 held by the separate retainer 21. Here, "the separate retainer 21 holds the three balls 6" means that the separate retainer 21 holds the three balls 6 to such an extent that the three balls 6 do not fall off due to its own weight.

[0028] In the rolling path C1, the three balls 6 held by the separate retainer 21 roll under load, and the separate retainer 21 moves together with the three balls 6. In the return path C2 and turn path C3, the separate retainer 21 moves while being pushed by the succeeding separate retainer 21 and balls 6, and the three balls 6 held by the separate retainer 21 move together with the separate retainer 21.

[0029] The following describes in detail the configuration of the separate retainer 21. For ease of explanation, the following describes the configuration of the separate retainer 21 using the moving direction of the separate retainer 21, the width direction perpendicular to the moving direction, and the height direction perpendicular to the moving direction and the width direction, as shown in Figs. 7 and 8.

[0030] As shown in FIG. 7, the separate retainer 21 holds one ball 6a in one row and two balls 6b in the other row. The separate retainer 21 has a shape combining a T and an O in a plan view (see FIG. 8(a)), and has three housing sections 21a, 21b in which the three balls 6a, 6b are housed. The material of the separate retainer 21 is not particularly limited, and may be, for example, a resin or an elastomer. The minimum diameter of the housing sections 21a, 21b is smaller than the ball diameter. When the balls 6a, 6b are housed in the housing sections 21a, 21b, the housing sections 21a, 21b are slightly elastically deformed.

[0031] As shown in Figure 7, the separate retainer 21 includes a pair of first spacer portions 22 provided at both ends in the traveling direction of one ball 6a in one row, a second spacer portion 23 provided between two balls 6b in the other row, and an intermediate portion 24 provided between the two rows of balls 6a, 6b and thinner than the first spacer portions 22 and second spacer portions 23.

[0032] The second spacer 23 is short cylindrical. At both ends in the moving direction of the second spacer 23, concave surfaces 23a are formed to match the spherical surfaces of the balls 6b so as to embrace the two balls 6b. No spacer is provided on the outward hemispheres 6b1 of the two balls 6b (the hatched parts in FIG. 8(a), the hemispheres opposite the opposing hemispheres 6b2).

[0033] As shown in Fig. 7, each of the pair of first spacer portions 22 has a short cylindrical shape. A concave surface 22a is formed on the ball 6a side of the first spacer portion 22 to match the spherical surface of the ball 6a so as to embrace the ball 6a. A flat surface 22b is formed on the end surface of the first spacer portion 22 in the traveling direction opposite the ball 6a. This flat surface 22b may be formed as a convex surface.

[0034] If the end face of the first spacer portion 22 facing the traveling direction opposite the ball 6a is formed into a concave surface, a force that tries to bend the separate retainer 21 acts on the first spacer portion 22 from the adjacent ball 6a on the turning path C3 (see FIG. 10). If this end face is formed into a flat surface 22b, only a force in the normal direction of the flat surface 22b acts on the first spacer portion 22 from the adjacent ball 6a, making it difficult for a force that tries to bend the separate retainer 21 to act on the first spacer portion 22.

[0035] As shown in Fig. 8(a), in a plan view of the separate retainer 21, the thickness t1 in the traveling direction of the first spacer portion 22 is thinner than the thickness t2 in the traveling direction of the second spacer portion 23. This is to make the pitch P of the balls 6a in one row L1 the same as the pitch P of the balls 6b in the other row L2, as shown in Fig. 6(a).

[0036] In the plan view shown in FIG. 8(a), the intermediate portion 24 is substantially doglegged. As shown in FIG. 7(a), the intermediate portion 24 is disposed in the center of the three balls 6 in the height direction, and is in contact with the great circles of the three balls 6. The intermediate portion 24 is thinner than the first spacer portion 22 and the second spacer portion 23. This prevents the separate retainer 21 from interfering with the circulation path 7 having a gourd-shaped cross section. The end face of the intermediate portion 24 on the side of one ball 6a is formed into a concave surface that matches the shape of the one ball 6a. Similarly, the end faces of the intermediate portion 24 on the side of the two balls 6b are formed into concave surfaces that match the shapes of the two balls 6b.

[0037] 8(a), in a plan view of the separate retainer 21, the separate retainer 21 includes a first band portion 25 provided on the outer side in the width direction of one ball 6a in one row, and a second band portion 26 provided on the outer side in the width direction of two balls 6b in the other row. The first band portion 25 and the second band portion 26 are inserted into the guide groove 7a of the circulation path 7.

[0038] In the plan view shown in Fig. 8(a), the first band portion 25 is substantially arc-shaped. Both ends of the first band portion 25 are connected to a pair of first spacer portions 22. As shown in Fig. 7(a), the first band portion 25 is disposed in the center of one ball 6a in the height direction and is in contact with the great circle of one ball 6a. The end face of the first band portion 25 on the side of one ball 6a is formed into a concave surface that matches the shape of one ball 6a.

[0039] In the side view of the separate retainer 21 shown in Figures 8(b) and 9(b), both end portions 25a of the first band portion 25 in the traveling direction are curved upward in Figure 9(b) so as to prevent contact with the guide groove 7a of the circulation path 7. In the plan view shown in Figure 8(a), the outer surface of the first band portion 25 is also formed in a substantially arc shape. This is also to prevent the first band portion 25 from contacting the guide groove 7a of the circulation path 7.

[0040] In the plan view shown in Fig. 8(a), the second band portion 26 is anchor-shaped. The center of the second band portion 26 is connected to the second spacer portion 23. As shown in Fig. 7(a), the second band portion 26 is disposed in the center in the height direction of the two balls 6b, and is tangent to the great circles of each of the two balls 6b. The end faces of the second band portion 26 on the side of the two balls 6b are formed into concave surfaces that match the spherical surfaces of the two balls 6b.

[0041] In the plan view shown in Fig. 8(a), claw portions 26a that come into contact with the outward hemispheres 6b1 of the two balls 6b (hatched portions in Fig. 8(a), hemispheres opposite the opposing hemispheres 6b2) are formed on both ends in the traveling direction of the second band portion 26. The claw portions 26a can prevent the two balls 6b from slipping out of the separate retainer 21 in the traveling direction.

[0042] In a side view of the separate retainer 21 shown in Fig. 9(b), both end portions 26a of the second band portion 26 in the traveling direction are curved upward in Fig. 9(b) so as to prevent contact with the guide groove 7a of the circulation path 7. In a plan view shown in Fig. 8(a), the outer surfaces of both end portions (claw portions) 26a of the second band portion 26 are also formed in a substantially arc shape. This is also to prevent the second band portion 26 from contacting the guide groove 7a of the circulation path 7.

[0043] 8(a), the separate retainer 21 (the intermediate portion 24, the pair of first spacer portions 22, and the first band portion 25) surrounds the entire circumference of one ball 6a, making it possible to easily hold one ball 6a.

[0044] The separate retainer 21 (middle portion 24, second spacer portion 23, second band portion 26) surrounds each of the two balls 6b by more than half a circumference but less than one circumference. In this embodiment, it surrounds approximately 2 / 3 of the circumference of each of the two balls 6b. This makes it easy to hold the two balls 6b. Also, as shown in FIG. 6(a), the pitch P of the ball 6a and the pitch P of the ball 6b can be kept constant. In contrast, if it is assumed that the separate retainer 21 surrounds the entire circumference of each of the two balls 6b, the balls 6b held by the separate retainer 21a and the balls 6b held by the separate retainer 21b must be separated, and the pitch P of the balls 6a and the pitch P of the balls 6b cannot be kept constant.

[0045] It is desirable to provide a gate in the second spacer portion 23 when resin molding the separate retainer 21. When resin molding, a weld line is formed in the center of the first band portion 25 in the traveling direction. However, since the length in the width direction of the first band portion 25 can be made relatively large, the formation of a weld line does not pose a problem.

[0046] 7(a), in a state where separate retainer 21 is held by a human hand or a robot hand, separate retainer 21 prevents three balls 6 from falling off. This makes it easier to assemble the motion guide device.

[0047] 10 to 12 show detailed views of the turning path C3 of the motion guide device. In Fig. 10 to 12, the end plate 5 has been removed. In the plan view shown in Fig. 11, the turning path C3 is curved in a U-shape. In the front view (longitudinal view of the rail 1) of Fig. 12(a), the turning path C3 is curved. Therefore, the turning path C3 of this embodiment is curved three-dimensionally.

[0048] As shown in FIG. 12, the turn path C3 has two rows of turn portions C31, C32 on which two rows of balls 6 are arranged. The total lengths of the two rows of turn portions C31, C32 are set to be approximately the same. In the plan view of FIG. 11, both end portions C31a of one turn portion C31 are arranged radially inward from both end portions C32a of the other turn portion C32. The center portion C31b of one turn portion C31 is arranged radially outward from the center portion C32b of the other turn portion C32. Therefore, the total lengths of the two rows of turn portions C31, C32 can be made approximately the same.

[0049] The effects of the motion guide device of this embodiment will be described below.

[0050] Since a plurality of separate retainers 21 that rotatably hold two rows of balls 6 are provided, the arrangement of the two rows of balls 6 can be maintained. The separate retainer 21 of this embodiment utilizes the principle that a plane is determined by three points (the centers of the three balls 6), and since the separate retainer 21 holds a total of three balls 6, elastic deformation of the separate retainer 21 on the turning path C3 can be suppressed. In contrast, if the separate retainer 21 holds four or more balls 6, it is difficult to arrange the centers of the four or more balls 6 within a plane on the turning path C3, so that the separate retainer 21 is more likely to elastically deform on the turning path C3.

[0051] Since the separate retainer 21 has a pair of first spacer portions 22, a second spacer portion 23, and an intermediate portion 24 that is thinner than the first spacer portions 22 and the second spacer portions 23, the separate retainer 21 can be prevented from interfering with the circulation path 7 having a gourd-shaped cross section.

[0052] Since separate retainer 21 includes first band portion 25 and second band portion 26, it becomes easy for separate retainer 21 to hold three balls 6.

[0053] Since separate retainer 21 surrounds the entire circumference of one ball 6a, it becomes easy for separate retainer 21 to hold one ball 6a.

[0054] Since the separate retainer 21 surrounds each of the two balls 6b by more than half a circumference but less than one circumference, it becomes easy for the separate retainer 21 to hold the two balls 6b. Also, the pitch P of the balls 6a and the pitch P of the balls 6b can be kept constant.

[0055] Since the end face of the first spacer portion 22 in the traveling direction opposite one of the balls 6a is formed into a flat surface 22b or a convex surface, it is possible to suppress the force acting from the adjacent balls 6 to bend the separate retainer 21.

[0056] In a plan view of the separate retainer 21, the thickness t1 in the traveling direction of the first spacer portion 22 is thinner than the thickness t2 in the traveling direction of the second spacer portion 23, so that the pitch P of the balls 6a and the pitch P of the balls 6b can be made substantially equal.

[0057] Since claw portions 26a that come into contact with the outward hemispheres 6b1 of the two balls 6b are formed on both ends of the second band portion 26 in the traveling direction, the two balls 6b can be prevented from slipping out of the separate retainer 21 in the traveling direction.

[0058] When viewed from the side of the separate retainer 21, at least a portion of the first band portion 25 and the second band portion 26 are curved so as not to come into contact with the guide groove 7a of the circulation path 7, thereby preventing the first band portion 25 and the second band portion 26 from rubbing against the wall surface of the guide groove 7a of the circulation path 7.

[0059] Since the separate retainer 21 prevents the three balls 6 from falling off when the separate retainer 21 is held by a human hand or a robot hand, the assembly of the motion guide device becomes easy.

[0060] When viewed from the moving direction of the separate retainer 21, one ball 6a and two balls 6b overlap each other, so that the circulation path 7 can be made compact.

[0061] The separate retainer 21 of the present embodiment is suitable for a motion guide device in which the turning path C3 is curved three-dimensionally. Second embodiment

[0062] 13 and 14 show a separate retainer 41 according to a second embodiment of the present invention. In the side view of the separate retainer 41 shown in FIG. 14(b), the rail 1 is located below the three balls 6a and 6b, and the carriage 2 is located above them. When the carriage 2 moves leftward relative to the rail 1, the three balls 6a and 6b rotate leftward along with the carriage 2. At this time, the left side of the separate retainer 41 is lowered by the left rotation of the two balls 6b, and the right side of the separate retainer 41 is raised by the left rotation of the two balls 6b. This may cause the separate retainer 41 to tilt. If the separate retainer 41 tilts, the first band portion 25 and the second band portion 26 may rub against the wall surface of the guide groove 7a of the circulation path 7.

[0063] In order to prevent the separate retainer 41 from tilting, in the second embodiment, in the side view of the separate retainer 41 shown in Fig. 14(b), the claw portions 26a at both ends of the second band portion 26 are formed with padding portions 26a1 that come into contact with the lower hemispheres 6b3 (hatched portions in Fig. 14(b)) of the two balls 6b. By forming the padding portions 26a1 in this manner, it is possible to prevent the right side of the separate retainer 41 from being lifted up by the left rotation of the two balls 6b. This makes it possible to prevent the separate retainer 41 from tilting.

[0064] On the other hand, when the carriage 2 moves to the right relative to the rail 1, the three balls 6a, 6b rotate to the right. By forming the padding portion 26a1, it is possible to prevent the left side of the separate retainer 41 from being lifted up by the right rotation of the two balls 6b. This makes it possible to prevent the separate retainer 41 from tilting.

[0065] In order to further prevent the separate retainer 41 from tilting, a padding portion that comes into contact with the lower hemisphere 6b3 of one of the balls 6a may be formed on both ends of the first band portion 25 in the traveling direction.

[0066] The pair of first spacer portions 22, second spacer portions 23, intermediate portion 24, first band portion 25, and second band portion 26 of separate retainer 41 are substantially the same as those of separate retainer 21 of the first embodiment, and therefore the same reference numerals are used and description thereof is omitted. However, in the second embodiment, first spacer portion 22 and second spacer portion 23 are D-cut to further avoid interference with circulation path 7. Also, in order to increase the strength of separate retainer 41, intermediate portion 24 is formed thicker than first band portion 25 and second band portion 26.

[0067] The present invention is not limited to being embodied in the separate retainer of the above embodiment, and can be embodied in other embodiments without departing from the spirit and scope of the present invention.

[0068] For example, in the above embodiment, two rows of balls are arranged in the circulation path of the motion guide device, but more than two rows of balls may be arranged.

[0069] In the above embodiment, the turning path of the motion guide device is curved three-dimensionally, but it may be curved two-dimensionally within a plane.

[0070] In the above embodiment, the rail extends straight, but it may be curved. [Explanation of symbols]

[0071] REFERENCE SIGNS LIST 1...rail, 2...carriage, 6...ball, 6a...ball in one row, 6b...ball in the other row, 7...circulation path, 21...separate retainer, 21a...one separate retainer, 21b...other separate retainer, 22...first spacer portion, 22b...flat surface, 23...second spacer portion, 24...middle portion, 25...first band portion, 26...second band portion, 41...separate retainer, C1...rolling path, C2...return path, C3...turn path

Claims

1. Rails and a carriage movable relative to the rail; At least two rows of balls are arranged in a circulating path including a rolling path between the rail and the carriage, a return path of the carriage, and a turning path of the carriage, a plurality of separate retainers for rotatably holding the at least two rows of balls; one separate retainer holds one ball in one row and two balls in the other row, for a total of three balls; The other separate retainer holds one ball in the other row and two balls in the one row, for a total of three balls.

2. The one separate retainer is a pair of first spacer portions provided at both ends in a direction in which one of the balls in one row travels; a second spacer provided between two balls in the other row; and 2. The motion guide device according to claim 1, further comprising an intermediate portion provided between the two rows of balls and thinner than the first spacer portion and the second spacer portion.

3. In a plan view of the one separate retainer, The one separate retainer includes a first band portion provided on an outer side of one of the balls in the one row in a width direction; 3. The motion guide device according to claim 2, further comprising: a second band portion provided on an outer side in a width direction of the two balls in the other row.

4. 3. The motion guide device according to claim 1, wherein the one separate retainer surrounds the entire circumference of one of the balls in the one row.

5. 3. The motion guide device according to claim 1, wherein the one separate retainer surrounds each of the two balls in the other row by more than half a circumference but less than one circumference.

6. 4. The motion guide device according to claim 2, wherein an end face of the first spacer portion in the traveling direction opposite to one of the balls in the one row is formed into a flat surface or a convex surface.

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