Motion guide device

Abstract

Provided is a motion guide device in which two rows of balls are arranged in a staggered pattern on a circulation path, wherein a carriage can be reduced in size and the durability of a retainer can be improved. At least one retainer (71), in which two rows of balls (6) are arranged in a staggered pattern, is provided to a circulation path including a rolling path (C1), a return path (C2), and a turning path (C3). At a rolling path (C1) end and a return path (C2) end of the turning path (C3) as seen from a direction perpendicular to a plane that includes the rolling path (C1) and the return path (C2) (see fig. 7(a)), a first turning path (21) for a first row of balls is arranged farther outward than a second turning path (22) for a second row of balls, and at the top of the turning path (C3), the first turning path (21) is arranged farther inward than the second turning path (22). The retainer (71) comprises: a center band (72) between the two rows of balls (6); and two side bands (73) on the outside of the two rows of balls (6). The two rows of balls (6) are separated as seen from the length direction of the retainer (71).

Description

Motion guiding device

[0001] The present invention relates to a motion guiding device in which two rows of balls are arranged staggeredly in a circulation path.

[0002] There is known a motion guiding device for guiding a movable body such as a table to linearly move or curve with respect to a base. The motion guiding device includes a guide rail and a carriage that relatively moves with respect to the guide rail. A plurality of balls are interposed between the guide rail and the carriage so as to be able to roll. The balls circulate in a circulation path including a rolling path between the guide rail and the carriage, a return path of the carriage, and a turn path of the carriage.

[0003] There has been proposed a motion guiding device in which two rows of balls are arranged staggeredly in a circulation path (see Patent Document 1). According to this motion guiding device, the number of effective balls can be increased, and since the two rows of balls alternately enter and exit the rolling path, the waving (ball passing vibration) of the carriage can be reduced.

[0004] Japanese Patent Application Laid-Open No. 2014-055670 (FIG. 17)

[0005] However, in the conventional motion guiding device, there is a problem that the carriage tends to be enlarged. If the outer dimensions of the carriage do not conform to the ISO dimensions, it cannot be replaced from other motion guiding devices that conform to the ISO dimensions.

[0006] Further, when two rows of balls arranged staggeredly are held by a retainer, the elastic deformation of the retainer is forced in the turn path, so there is a problem in the durability of the retainer.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a motion guiding device in which two rows of balls are arranged staggeredly in a circulation path, capable of reducing the size of the carriage and improving the durability of the retainer.

[0008] To solve the above problems, one aspect of the present invention provides a motion guide device comprising a guide rail having a rolling portion, and a carriage having a rolling portion facing the rolling portion, a return path, and a turn path, wherein at least one retainer is provided in a circulation path including the rolling path, the return path, and the turn path between the rolling portion of the guide rail and the rolling portion of the carriage, and two rows of balls are arranged in a staggered pattern, and when viewed from a direction perpendicular to the plane including the rolling path and the return path, the first turn path for the first row of balls is positioned outside the second turn path for the second row of balls at the rolling path side end and the return path side end of the turn path, and the first turn path is positioned inside the second turn path at the top of the turn path, and the retainer comprises a center band between the two rows of balls and two side bands outside the two rows of balls, and the two rows of balls are separated when viewed in the longitudinal direction of the retainer.

[0009] According to the present invention, by forming the turn path in the shape described above, the degree of freedom in the layout of the rolling path and return path connected to the turn path can be increased. As a result, the carriage can be made smaller. In addition, by using a three-band configuration (center band and two side bands), two rows of balls can be held, and since the two rows of balls are spaced apart when viewed from the length direction of the retainer, the width of the center band can be secured and its strength increased. As a result, the durability of the retainer can be improved.

[0010] Figure 3(a) is a perspective view (including a partial cross-sectional view) of a motion guide device according to an embodiment of the present invention. Figure 3(c) is a right-angle cross-sectional view of the guide rail of the motion guide device according to an embodiment of the present invention. Figure 3(a) is an enlarged cross-sectional view of the rolling path, Figure 3(b) is an enlarged cross-sectional view of the return path, and Figure 3(c) is an enlarged cross-sectional view of the top of the turn path. This is a perspective view of the inner plate. This is a perspective view of the end plate. Figure 6(a) is a perspective view of the upper left turn path in Figure 2, and Figure 6(b) shows the first ball passage trajectory and the second ball passage trajectory viewed from the same direction as in Figure 6(a). Figure 7(a) is a plan view of the turn path viewed from the direction of arrow A in Figure 6(a), Figure 7(b) is a front view of the turn path, and Figure 7(c) is a side view of the turn path. Figures 8(a), 8(b), and 8(c) show the first ball passage trajectory and the second ball passage trajectory viewed from the same direction as in Figures 7(a), 8(b), and 8(c). This is a diagram illustrating the method for forming the first ball passage trajectory and the second ball passage trajectory. This is a perspective view of a retainer with two rows of balls arranged in a staggered pattern. Figure 11(a) is a side view of the retainer, and Figure 11(b) is a bottom view of the retainer. Figure 12(a) is an enlarged view of a part of Figure 11(a), and Figure 12(b) is an enlarged view of a part of Figure 11(b). Figure 13(a) is a front view of the retainer, and Figure 13(b) is a cross-sectional view of Figure 11(a). This figure shows an example in which five retainers are provided in a circulation path. This figure shows an example in which two rows of spacer balls are arranged in a staggered pattern on the front and rear retainers in the direction of travel.

[0011] Hereinafter, an embodiment of the motion guidance device of the present invention will be described based on the attached drawings. However, the motion guidance device of the present invention can be embodied in various forms and is not limited to the embodiments described herein. This embodiment is provided with the intention that those skilled in the art will be able to fully understand the invention by making full disclosures in the specification.

[0012] For the sake of clarity, in the following explanation, the configuration of the motion guide device will be described using the orientation of the motion guide device when viewed from the relative direction of movement of the carriage, i.e., the up / down, left / right, and front / back directions in Figures 1 and 2. Of course, the arrangement of the motion guide device is not limited to this.

[0013] As shown in Figure 1, the motion guide device comprises a guide rail 1 and a carriage 2 that can move relative to the guide rail 1. The motion guide device is used to guide the linear or curved motion of a movable body such as a table. The guide rail 1 is attached to a base or the like (not shown). The carriage 2 is attached to a movable body such as a table (not shown).

[0014] Two protrusions 11 projecting in the left-right direction are formed on the upper part of the guide rail 1. Two rolling parts 12 are formed on each protrusion 11, one above the other. Each rolling part 12 has two parallel rolling grooves 1a. Two rows of balls 6 roll in these two rolling grooves 1a. Each rolling groove 1a is a circular arc groove with a cross-section of, for example, a single circular arc. Mounting holes 1b are made in the guide rail 1 for attaching the guide rail 1 to a base or the like.

[0015] On the upper and lower sides of both the left and right sides of the carriage 2, for example, four circulation paths 7 are provided for circulating the balls 6. Figure 1 shows the two circulation paths 7 on the right side. Each circulation path 7 comprises a straight rolling path C1 between the rolling section 12 of the guide rail 1 and the rolling section 13 of the carriage 2, a return path C2 parallel to the rolling path C1, and a roughly U-shaped turn path C3 connected to the rolling path C1 and the return path C2. The return path C2 and the turn path C3 are provided on the carriage 2.

[0016] The circulation path 7 is provided with at least one retainer 71, for example, three or more, preferably four or more, on which two rows of balls 6 are arranged in a staggered pattern. In the rolling path C1, the two rows of balls 6 roll under load. The retainer 71 moves together with the two rows of balls 6. In the turn path C3 and the return path C2, the retainer 71 moves while being pushed by the subsequent retainer 71.

[0017] The carriage 2 comprises a carriage body 3, inner plates 4 attached to both end faces of the carriage body 3, and end plates 5 attached to both end faces of the carriage body 3 so as to cover the inner plates 4. The carriage body 3 is provided with a rolling section 13 and a return path C2. The inner plates 4 and end plates 5 are provided with turn paths C3.

[0018] As shown in the cross-sectional view of Figure 2, the carriage body 3 is roughly U-shaped and has a central portion 3a facing the upper surface of the guide rail 1 and left and right sleeve portions 3b facing the left and right sides of the guide rail 1. Rolling portions 13 are formed above and below the left and right sleeve portions 3b, facing the rolling portion 12 of the guide rail 1.

[0019] As shown in the enlarged cross-sectional view of the rolling path C1 in Figure 3(a), the rolling section 13 has two parallel rolling grooves 3c on which two rows of balls 6 roll. Each rolling groove 3c is a circular arc groove with a cross-section of, for example, a single circular arc. The rolling path C1 is formed between the rolling section 13 of the carriage body 3 and the rolling section 12 of the guide rail 1. The rolling path C1 comprises a first rolling path 21 for the first row of balls 6 and a second rolling path 22 for the second row of balls 6. The second row of balls 6 are separated when viewed from the longitudinal direction of the rolling path C1. The sign θ in Figure 2 is the contact angle representing the direction in which the two rows of balls 6 are subjected to load. The contact angle θ is set to, for example, 30 to 60°.

[0020] As shown in Figure 2, through holes 14 are formed parallel to the rolling parts at the top and bottom of the left and right sleeve portions 3b of the carriage body 3. A pipe 8 is inserted into the through holes 14. A return path C2 is formed inside the pipe 8. 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.

[0021] As shown in the enlarged cross-sectional view of the return passage C2 in Figure 3(b), the return passage C2 comprises a first return passage 21 for the first row of balls 6 and a second return passage 22 for the second row of balls 6. There is a gap between the first return passage 21 and the balls 6, and there is a gap between the second return passage 22 and the balls 6. A groove 10 is formed in the return passage C2 into which the side band 73 of the retainer 71 fits.

[0022] As shown in Figure 4, the inner plate 4 is roughly U-shaped and has a central portion 4a facing the upper surface of the guide rail 1 and left and right sleeve portions 4b facing the left and right sides of the guide rail 1. R-piece portions 31 that are roughly semi-cylindrical are provided above and below the left and right sleeve portions 4b of the inner plate 4. Two inner turn grooves 31a that constitute the inner circumference of the turn path C3 are formed on the outer circumference of the R-piece portion 31.

[0023] In Figure 4, reference numeral 31d indicates the end of the inner circumferential turn groove 31a on the return path C2 side. Reference numeral 31c indicates the end of the inner circumferential turn groove 31a on the rolling path C1 side. Reference numeral 31b indicates the transition portion of the guide rail 1 facing the rolling portion 12.

[0024] As shown in Figure 5, the end plate 5 is also roughly U-shaped and has a central portion 5a facing the upper surface of the guide rail 1 and left and right sleeve portions 5b facing the left and right sides of the guide rail 1. Recesses 32 into which the R-piece portion 31 is fitted are formed on the upper and lower parts of the left and right sleeve portions 5b of the end plate 5. Two outer peripheral turn grooves 32a that constitute the outer peripheral side of the turn path C3 are formed in the recesses 32. The end plate 5 and the inner plate 4 are fixed to the carriage body 3, for example, by screws. Through holes 37 and 38 for screws are formed in the end plate 5 and the inner plate 4.

[0025] As shown in the enlarged cross-sectional view of the top of the turn path C3 in Figure 3(c), two inner circumferential turn grooves 31a are formed in the inner plate 4. Two outer circumferential turn grooves 32a are formed in the end plate 5. Grooves 30 into which the retainer's side band fits are formed in the inner plate 4 and the end plate 5. The turn path C3 comprises a first turn path 21 for the first row of balls 6 and a second turn path 22 for the second row of balls 6. There is a gap between the first turn path 21 and the balls 6, and a gap between the second turn path 22 and the balls 6.

[0026] The shape of the turn path C3 is described below. Figure 6(a) shows a perspective view of the turn path C3 in the upper left of Figure 2. Reference numeral 1 denotes a guide rail, reference numeral 4 denotes an inner plate, and reference numeral C3 denotes a turn path. As described above, the turn path C3 comprises a first turn path 21 for the first row of balls 6 and a second turn path 22 for the second row of balls 6.

[0027] Figure 6(b) shows the trajectory of the center of the first row of balls 6 (first ball trajectory 41) and the trajectory of the center of the second row of balls 6 (second ball trajectory 42), viewed from the same direction as in Figure 6(a). The first ball trajectory 41 and the second ball trajectory 42 are three-dimensional curves.

[0028] Figure 7(a) shows a plan view of the turn path C3 as seen from direction A perpendicular to the plane P (the plane P that includes the center of the turn path C1 and the center of the return path C2 as shown in Figure 2) which contains the rolling path C1 and the return path C2. Figure 7(b) shows a front view of the turn path C3. Figure 7(c) shows a side view of the turn path C3 as seen from the direction in which the rolling path C1 and the return path C2 overlap. Figures 8(a), (b), and (c) show the first ball trajectory 41 and the second ball trajectory 42 as seen from the same direction as in Figures 7(a), (b), and (c).

[0029] As shown in Figure 8(a), when viewed from direction A perpendicular to the plane P containing the rolling path C1 and the return path C2, the first ball trajectory 41 is positioned outside the second ball trajectory 42 at the end Q1 on the rolling path C1 side and the end Q2 on the return path C2 side of the turn path C3. In other words, the distance L1 between the points Q1 and Q2 is greater for the first ball trajectory 41 than for the second ball trajectory 42. Also, at the top Q3 of the turn path C3, the first ball trajectory 41 is positioned inside the second ball trajectory 42. In other words, the projection distance L2 of the top Q3 is smaller for the first ball trajectory 41 than for the second ball trajectory 42.

[0030] As shown in Figure 8(b), in a front view of the turn path C3, the first ball trajectory 41 and the second ball trajectory 42 curve upwards. As shown in Figure 8(c), in a side view, the first ball trajectory 41 and the second ball trajectory 42 of the turn path C3 curve downwards. The symbol Q3 indicates the top of the turn path C3.

[0031] As shown in Figures 9(a) and 9(b), the first ball trajectory 41 and the second ball trajectory 42 are formed, for example, by bending a rectangular virtual plate VP. As shown in Figure 9(a), the length M1 of the short sides 61a and 61b of the virtual plate VP is set to the distance M1 between the first ball trajectory 41 and the second ball trajectory 42, and the length M2 of the long sides 62a and 62b is set to the circumference of the first ball trajectory 41 and the second ball trajectory 42. Then, as shown in Figure 9(b), when this virtual plate VP is curved into a U-shape and the short sides 61a and 61b of the virtual plate VP are twisted to match the opening angles of the ends Q1 and Q2 of the turn path C3, the shape of the long side 62a of the virtual plate VP is the shape of the first ball trajectory 41, and the shape of the long side 62b of the virtual plate VP is the shape of the second ball trajectory 42.

[0032] The retainer 71 is described below. As shown in Figure 10, the retainer 71 has two rows of balls 6 arranged in a staggered pattern. The first row of balls 6 is arranged at a constant pitch, and the second row of balls 6 is also arranged at a constant pitch. The ball pitch of the first row of balls 6 and the second row of balls 6 are offset by 1 / 2. The number of balls 6 in the first row is not particularly limited, for example, 5 to 30. The number of balls 6 in the second row is not particularly limited, for example, 5 to 30. The retainer 71 is manufactured by injection molding of resin. The retainer 71 is flexible so that it can move along the circulation path 7.

[0033] The retainer 71 comprises a center band 72 between two rows of balls 6 and two side bands 73 outside the two rows of balls. The center band 72 and the side bands 73 are of the same thickness. As shown in Figure 11(a), the center band 72 and the two side bands 73 are positioned below the center of the balls 6. As shown in the bottom view of the retainer 71 in Figure 11(b), the center band 72 and the two side bands 73 of the retainer 71 have substantially circular first ball housing sections 74 formed at a constant pitch for housing the first row of balls 6, and substantially circular second ball housing sections 75 formed at a constant pitch for housing the second row of balls 6.

[0034] The retainer 71 has a first intermediate spacer 76 integrally formed between adjacent balls 6 in the first row, and a second intermediate spacer 77 integrally formed between adjacent balls 6 in the second row. The first intermediate spacer 76 is substantially cylindrical in shape. The first intermediate spacer 76 has a spherical recess 76a that contacts the adjacent ball 6. The second intermediate spacer 77 is also substantially cylindrical in shape. The second intermediate spacer 77 has a spherical recess 77a that contacts the adjacent ball 6. Flat surfaces 76b and 77b are formed at the lower parts of the first intermediate spacer 76 and the second intermediate spacer 77 to avoid interference with the inner circumference of the circulation path 7.

[0035] At both ends of the retainer 71 in the longitudinal direction, a first end spacer 78 is integrally formed to contact the ball 6 at the end of the first row, and a second end spacer 79 is integrally formed to contact the ball 6 at the end of the second row. The first end spacer 78 is a disc shape and thinner than the first intermediate spacer 76. The first end spacer 78 has a spherical recess 78a that contacts the ball 6 at the end of the first row. The second end spacer 79 is a substantially disc shape and thinner than the second intermediate spacer 77. The second end spacer 79 has a spherical recess 79a that contacts the ball 6 at the end of the second row.

[0036] As shown in Figures 11(a) and 12(a), when the retainer 71 is positioned horizontally, the first end spacer 78 and the second end spacer 79 are positioned below the first intermediate spacer 76 and the second intermediate spacer 77 (in other words, on the inner circumference side of the circulation path 7).

[0037] As shown in Figures 11(b) and 12(b), both ends of the retainer 71 in the longitudinal direction are formed in a stepped shape. Inclined portions 72a are formed at both ends of the center band 72 in the longitudinal direction so as to connect the first end spacer 78 and the second end spacer 79. The inclination angle α of the inclined portion 72a is, for example, 20° to 40°.

[0038] As shown in Figure 13(a), the two rows of balls 6 are spaced apart when viewed along the length of the retainer 71. The end faces 78b and 79b of the first end spacer 78 and the second end spacer 79 are formed flat. The spacer balls 81 are in contact with these end faces 78b and 79b. Chamfers are formed on the upper parts 78c and 79c of the first end spacer 78 and the second end spacer 79.

[0039] As shown in Figure 14, the circulation path 7 is provided with three or more, preferably four or more, and more preferably four to six retainers 71. Figure 14 shows five retainers 71. Between the front and rear retainers 71 in the direction of travel, spacer balls 81 not held by the retainers 71 are arranged. As shown in Figure 15, the retainer 71 has two rows of balls 6 arranged in a staggered pattern, and the two spacer balls 81 are also arranged in a staggered pattern. One of the two spacer balls 81 is in contact with the first end spacer 78 of the front and rear retainers 71, and the other is in contact with the second end spacer 79 of the front and rear retainers 71.

[0040] The effects of the motion guidance device of this embodiment will be explained below.

[0041] By forming the turn path C3 in the three-dimensional shape described above, the degree of freedom in the layout of the rolling path C1 and return path C2 connected to the turn path C3 can be increased. For example, as shown in Figure 2, the upper return path C2 can be positioned below the contact angle line N1 of the upper two rows of balls 6, and the lower return path C2 can be positioned above the contact angle line N2 of the lower two rows of balls 6. This makes it possible to miniaturize the carriage 2.

[0042] By using three bands for the retainer (center band 72 and two side bands 73), it is possible to hold two rows of balls 6. Also, since the two rows of balls 6 are separated when viewed in the length direction of the retainer 71, the width of the center band 72 can be ensured. As shown in Fig. 11(b), for example, when gate positions 76c and 77c for injection molding are arranged in every other first intermediate spacer 76 and every other second intermediate spacer 77, a weld line occurs in the center band 72. However, by ensuring the width of the center band 72, a reduction in strength due to the weld line can be prevented. Therefore, the durability of the retainer 71 can be improved.

[0043] Since two spacer balls 81 are arranged in a staggered manner between adjacent retainers 71 in the front and rear in the advancing direction, the bending at the end of the retainer 71 in the turn path C3 can be alleviated, and the durability of the retainer 71 can be improved.

[0044] Since the end faces 78b and 79b of the first end spacer 78 and the second end spacer 79 of the retainer 71 are formed flat, the bending at the end of the retainer 71 can be further alleviated.

[0045] Since four or more retainers 71 are provided in the circulation path 7, the length of each retainer 71 can be shortened, and the durability of the retainer 71 moving in the turn path C3 with a complex three-dimensional shape can be improved. When the number of retainers 71 is seven or more, it is troublesome to incorporate the retainers 71 into the circulation path 7, so the number of retainers 71 is preferably 4 to 6.

[0046] In a state where the retainer 71 is arranged on a horizontal plane, since the first end spacer 78 and the second end spacer 79 are arranged below the first intermediate spacer 76 and the second intermediate spacer 77, it is possible to prevent the first end spacer 78 and the second end spacer 79 from contacting the outer peripheral side of the turn path C3.

[0047] In a state where the retainer 71 is arranged on a horizontal plane, since the center band 72 and the two side bands 73 are arranged below the center of the first row of balls 6 and the center of the two rows of balls 6, the bending strength of the retainer 71 and the holding strength of the balls 6 can be improved.

[0048] This specification is based on Japanese Patent Application No. 2024-164946 filed on September 24, 2024. All of its contents are incorporated herein.

[0049] 1... guide rail, 2... carriage, 6... ball, 7... circulation path, 12... rolling part of the guide rail, 13... rolling part of the carriage, C1... rolling path, C2... return path, C3... turn path, P... plane including the rolling path and the return path, A... direction perpendicular to the plane including the rolling path and the return path, Q1... end on the rolling path side of the turn path, Q2... end on the return path side of the turn path, Q3... top of the turn path, 21... first turn path for the balls in the first row, 22... second turn path for the balls in the second row, 71... retainer, 72... center band, 73... side band, 76... first intermediate spacer between the balls in the first row, 77... second intermediate spacer between the balls in the second row, 78... first end spacer, 79... second end spacer, 81... spacer ball

Claims

1. A motion guide device comprising: a guide rail having a rolling section; and a carriage having a rolling section opposite to the rolling section, a return path, and a turn path, wherein at least one retainer is provided in a circulation path including the rolling path, the return path, and the turn path between the rolling section of the guide rail and the rolling section of the carriage, wherein two rows of balls are arranged in a staggered pattern, and as viewed from a direction perpendicular to the plane including the rolling path and the return path, the first turn path for the first row of balls is positioned outside the second turn path for the second row of balls at the rolling path side end and the return path side end of the turn path, and the first turn path is positioned inside the second turn path at the top of the turn path, and the retainer comprises a center band between the two rows of balls and two side bands outside the two rows of balls, wherein the two rows of balls are separated as viewed from the length direction of the retainer.

2. The motion guide device according to claim 1, characterized in that two spacer balls not held by the retainers are arranged in a staggered pattern between adjacent retainers in the front and rear directions of travel.

3. The motion guide device according to claim 2, characterized in that the end faces of the first end spacer and the second end spacer, which are arranged at the longitudinal ends of the retainer, are formed to be flat.

4. The motion guidance device according to claim 1 or 2, characterized in that four or more retainers are provided in the circulation path.

5. The motion guide device according to claim 1 or 2, characterized in that, when the retainer is positioned on a horizontal plane, the first end spacer and the second end spacer, which are positioned at the longitudinal ends of the retainer, are positioned below the first intermediate spacer between the balls in the first row and the second intermediate spacer between the balls in the second row.

6. The motion guide device according to claim 1 or 2, characterized in that, when the retainer is positioned on a horizontal plane, the center band and the two side bands are positioned below the center of the first row of balls and the center of the second row of balls.

7. The motion guidance device according to claim 1 or 2, characterized in that at least one retainer is provided in each of the four circulation paths.

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