MULTI-RAY ROLLING ENERGY HOUSING BELT AND MOTION GUIDE DEVICE

Abstract

Multi-row rolling element housing strip, wherein at least three rows of rolling elements (17-19, 33-36) are arranged in a strip (11, 31) and in at least one part of the strip (11, 31) in a longitudinal direction thereof, second rolling elements (18a, 34a) of a second row of rolling elements (18, 34) are displaced by P / n in the longitudinal direction of the strip (11, 31) from first rolling elements (17a, 33a) of a first row of rolling elements (17, 33), third rolling elements (19a, 35a) of a third row of rolling elements (19, 35) are displaced by P / n in the longitudinal direction from the second rolling elements (18a, 34a), the third rolling elements (19a, 35a) by 2P / n in the longitudinal direction from the first rolling elements (17a, 33a) are displaced, a first to third opening section row (15a, 15b, 15c) in which a plurality of the first rolling elements (17a, 33a), of the first row of rolling elements (17, 33), a plurality of the second rolling elements (18a, 34a) of the second row of rolling elements (18, 34), and a plurality of the third rolling elements (19a,35a) of the third row of rolling elements (19, 35) are housed in a single band, and P is a rolling element division of the first to third rows of rolling elements (17-19, 33-35) and n is the number of rows of rolling elements.

Description

Technical FieldThe present invention relates to a multi-row rolling element case band integrated in a circulation path of a carriage of a motion guide device and a motion guide device.Background ArtA motion guide device guides the motion of a movable body such as a table using the rolling motion of rolling elements such as balls or rollers. The movement guide device includes a guide rail and a carriage that relatively moves along the guide rail. A plurality of rolling elements such as balls or rollers are disposed between the guide rail and the carriage so as to be capable of rolling motion. The carriage is provided with a circulation path on which the rolling bodies circulate. When the carriage moves relatively along the guide rail, the rolling elements circulate in the circulation path.The rolling elements that roll between the guide rail and the carriage roll in the same direction. In order to prevent upstream and downstream rolling elements from rubbing against each other in the rolling direction and hindering smooth rolling of the rolling elements, a rolling element housing band in which spacers are disposed between the rolling elements and the spacers are coupled via a band in a chain has been proposed (see Patent Literature 1).Further relevant prior art is disclosed in the following documents: U.S. Pat. No. 2015 0 159 695 A1 and JP 2014 55 670 A.Citation ListPatent LiteraturePatent Literature 1: JP 2008-249043 ASUMMARY OF THE INVENTIONTechnical ProblemA rolling guide using rolling motion of rolling elements has an advantage that the guide has higher rigidity than a hydrostatic guide, i.e., a system that supplies a liquid such as oil to a guide surface, floats a movable body, and guides the movable body by low viscosity of the fluid. Thus, in recent years, rolling guides also replace hydrostatic guides in machines such as precision machining machines, high-precision machining centers, and semiconductor manufacturing apparatuses. How precisely a movable body is guided becomes a problem when using a roller guide device in such a machine.When the diameter of a rolling element is reduced and the number of rolling elements between a guide rail and a carriage is increased, it can be assumed that the rolling elements are an oil layer of a hydrostatic guide. An increase in the degree of precision of a guide can be promoted. However, there is a limit to a reduction in the diameter of a rolling element in terms of production technology.An object of the present invention is therefore to provide a multi-row rolling element housing band in which an increase in the degree of precision of a guide can be promoted, and a motion guide device in which the multi-row rolling element housing band is integrated.Solution of the ProblemTo solve the above-described problem, a multi-row rolling element casing band having the features of claim 1 is provided. In addition, a movement device having the features of claim 4 is specified. This comprises the multi-part rolling body housing band according to the invention. Moreover, according to a subordinate aspect, there is provided the motion guiding device having the features of claim 5.Advantageous Effects of the InventionAccording to one aspect of the present invention, the rolling elements of each row of rolling elements do not completely overlap when viewed in the width direction of a band. Accordingly, it can be considered that the number of rolling elements that contribute to a reduction in the ripple of a carriage has increased. Therefore, it is possible to promote a decrease in the curl of the carriage and hence an increase in the degree of precision of a guide.Brief Description of the DrawingsFIG. 1 is a cross-sectional view of a motion guide device of a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIGS. 3A to 3D are four orthogonal views of a ball cage of the first embodiment of the present invention (FIG. 3A is a plan view, FIG. 3B is a front view, FIG. 3C is a bottom view, and FIG. 3D is a left side view). FIG. 4 is an enlarged plan view of the ball cage of the embodiment. FIG. 5 is an enlarged front view of the ball cage of the embodiment. FIG. 6 is a diagram explaining the principle of occurrence of waves. FIGS. 7A to 7F are plan views showing modifications of the ball holder of the embodiment. FIGS. 8A to 8D are four orthogonal views of a ball cage of a second embodiment of the present invention (FIG. 8A is a plan view, FIG. 8B is a front view, FIG. 8C is a bottom view, and FIG. 8D is a left side view). FIG. 9 is an enlarged plan view of the ball cage of the embodiment. FIG. 10 is an enlarged front view of the ball cage of the embodiment. FIG. 11 is a plan view of a modification of the ball holder of the embodiment. FIG. 12 is a perspective view (including a partial cross-sectional view) of a motion guide device of the second embodiment of the present invention. FIGS. 13A and 13B are diagrams illustrating a cage integrated with the motion guide device of the embodiment (FIG. 13A is a plan view and FIG. 13B is a front view). FIGS. 14A to 14C are plan views of cages used for analysis (FIG. 14A is a first comparative example, FIG. 14B is a second comparative example, and FIG. 14C is an example of the present invention). FIGS. 15A and 15B are diagrams illustrating the results of wave analysis (FIG. 15A illustrates the wave motion in the radial direction and FIG. 15B illustrates the wave motion in the inclination direction).DESCRIPTION OF THE EMBODIMENTSFIGS. 1 and 2 illustrate a motion guide device 1 in which a multi-row rolling element housing band 11 of a first embodiment of the present invention is integrated. FIG. 1 is a cross-sectional view of the motion guide device 1 taken along a plane orthogonal to a guide rail 2. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1.The motion guide device 1 of the first embodiment shown in FIG. 1 and a motion guide device 41 of a second embodiment shown in FIG. 12 differ in whether three ball rows are provided in the multi-row rolling element housing band 11 or two ball rows are provided in a multi-row rolling element housing band 42. However, the basic structures of the guide rail 2 and a carriage 3 are substantially the same. In the description of the motion guide device 1 of the first embodiment of FIG. 1, the description is given with reference also to FIG. 12. Moreover, for convenience of description, the configuration of the motion guide device 1 will be described using the directions in which the motion guide device 1 is disposed on a horizontal plane and viewed from the front, i.e., upper and lower, left and right, and front and rear in FIGS. 1 and 12.As illustrated in FIG. 1, the movement guide device 1 includes the guide rail 2 and the carriage 3 mounted on the guide rail 2 so as to be movable relative to the guide rail 2. The carriage 3 is provided on each of the left and right sides with two upper and lower track-shaped circulation paths 4 (see FIG. 12 ). The multi-row rolling element housing band 11 is accommodated in each circulation path 4.The guide rail 2 is long in the front and rear directions. A total of four ball rolling grooves 5 as rolling element rolling grooves are formed on the left and right sides of the guide rail 2, two upper and lower ball rolling grooves 5 on each side. The cross-sectional shape of the ball rolling groove 5 has a shape of three combined arcs 2a, 2a and 2a. The three arches 2a, 2a and 2a have a radius somewhat larger than the radius of a ball 6, and a through bore 2b is made in the guide rail 2 for fixing the guide rail 2, for example on a base.As illustrated in FIG. 2, the carriage 3 includes a carriage body 7, an inner plate 8 mounted on each end surface of the carriage body 7 in a relative movement direction thereof, and an end plate 9 mounted on each end surface of the carriage body 7 so as to cover the inner plate 8 (see also FIG. 12 ).As shown in FIG. 1, the carriage body 7 has an inverted U-shape in cross section and includes a center portion 7 afacing an upper side of the guide rail 2 and left and right arm portions 7 bfacing side surfaces of the guide rail 2. Loaded ball rolling grooves 10 as rolling elements, rolling grooves facing the ball rolling grooves 5 of the guide rail 2, are formed on the arm portion 7 bof the slide body 7. The cross-sectional shape of the loaded ball rolling groove 10 has a shape of three combined arcs 7c, 7c and 7c. The three arcs 7c, 7c and 7c have a slightly larger radius than the radius of the ball 6.As shown in FIG. 2, each circulation path 4 includes a linear loaded path C 1, a linear return path C 2 substantially parallel to the loaded path C 1, and U-shaped turning paths C 3 connecting the loaded path C 1 and the return path C 2.The loaded path C1 is formed between the loaded ball rolling groove 10 of the carriage body 7 and the ball rolling groove 5 of the guide rail 2. As shown in FIG. 1, the through holes 12 are formed in the form of three combined arcs parallel to the loaded ball rolling grooves 10 in the arm portions 7b of the carriage body 7. The return path C 2 is formed in the through hole 12. A return passage component 13 adapted to the shape of the through bore 12 is inserted into the through bore 12. The cross-sectional shape of the return path C2 is based on three circles which have a slightly larger diameter than the diameter of the ball 6 and overlap each other.As shown in FIG. 2, the turning path C 3 is formed between the inner plate 8 and the end plate 9. The inner panel 8 has an inverted U-shape in front view, and includes a central portion 8 athat faces the upper side of the guide rail 2 and a pair of left and right arm portions 8 bthat face the side surfaces of the guide rail 2 (see FIG. 12 ). An inner side of the turning path C3 is formed on the arm portion 8b of the inner plate 8. The end plate 9 also has an inverted U shape in front view, and includes a center portion 9 afacing the upper side of the guide rail 2 and a pair of left and right arm portions 9 bfacing the side surfaces of the guide rail 2 (see FIG. 12 ). An outer side of the turning path C 3 is formed on the end plate 9.FIGS. 3A to 3D illustrate four orthogonal views of the multi-row rolling element housing band 11 of the embodiment. FIG. 3A is a plan view, FIG. 3B is a front view, FIG. 3C is a bottom view, and FIG. 3D is a left side view. The rear view is the same as the front view. The right side view is the same as the left side view. In the following description of the multi-row roller housing tape 11, the configuration of the multi-row roller housing tape 11 having a width direction and a longitudinal direction illustrated in FIG. 3A and a thickness direction illustrated in FIG. 3B will be described.As shown in FIG. 3A, three ball rows 17, 18 and 19 are arranged in a band 15 of the multi-row rolling element housing band 11. The ball rows are the first ball row 17, the second ball row 18, and the third ball row 19 in the order from one end to the other end in the width direction. Between the balls 17 a, 18 aand 19 aof the ball rows 17, 18 and 19 substantially short cylindrical spacers 20 are arranged. The ball pitch of each of the ball rows 17, 18 and 19 is kept constant. At each end portion of the spacer 20, a concave spherical portion corresponding to the shape of the first to third balls 17a, 18a and 19a is formed. The diameter of the first ball 17 aof the first ball row 17, the diameter of the second ball 18 aof the second ball row 18 and the diameter of the third ball 19 aof the third ball row 19 are the same. The ball pitch of the first ball row 17, the ball pitch of the second ball row 18 and the ball pitch of the third ball row 19 are also equivalent.As shown in FIG. 3A, each second ball 18 aof the second ball row 18 is displaced in the longitudinal direction of the band 15 from each first ball 17 aof the first ball row 17. Each third ball 19a of the third ball row 19 is displaced in the longitudinal direction of the band 15 of each first ball 17a and each second ball 18a. In other words, the positions of the first ball 17 a, the second ball 18 a, and the third ball 19 a, which are closest, are longitudinally displaced from each other in the longitudinal direction of the belt 15.As illustrated in FIG. 3B, each first ball 17 a, each second ball 18 a, and each third ball 19 ado not entirely overlap in the width direction (i.e., viewed from the front) (see also FIG. 5 ). However, a part of each first ball 17 a, a part of each second ball 18 a, and a part of each third ball 19 aadcreate.As illustrated in FIG. 3A, the band 15 is formed in a horizontal rectangular shape in plan view. In the band 15, three circular opening portion rows 15a, 15b and 15c are formed for receiving the three ball rows 17, 18 and 19. Between the opening portions of the three opening portion rows 15 a, 15 band 15 c, three spacer rows 20 a, 20 band 20 care provided. Each second spacer 20 of the second spacer row 20 bis displaced in the longitudinal direction of the band 15 by each first spacer 20 of the first spacer row 20 a. Each third spacer 20 of the third spacer row 20 cis displaced in the longitudinal direction of the band 15 by each first spacer 20 of the first spacer row 20 aand each second spacer 20 of the second spacer row 20 b. The spacers 20 and the tape 15 are integrally molded in resin. The three spacer rows 20a, 20b and 20c are coupled by the belt 15 in a chain. The band 15 is flexible to allow circulation along the track-shaped orbit 4.The band 15 is divided into four by the three ball rows 17, 18 and 19 and the three spacer rows 20a, 20b and 20c, i.e., a side band 21 protruding outward in the widthwise direction from the first ball row 17, a corrugated first middle band 22 between the first ball row 17 and the second ball row 18, a corrugated second middle band 23 between the second ball row 18 and the third ball row 19, and a side band 24 protruding outward in the widthwise direction from the third ball row 19. The first ball 17a and the second ball 18a are rendered non-contacting by the first center band 22. The second ball 18a and the third ball 19a are rendered non-contacting by the second central band 23. The distance between the first ball row 17 and the second ball row 18 is equal to the distance between the second ball row 18 and the third ball row 19.Both end portions of the band 15 in the longitudinal direction are formed in a step shape. One or more multi-row rolling body housing bands 11 are integrated into the circulatory path 4. When joining both end sections of a multi-row rolling element housing strip 11 or when joining adjacent multi-row rolling element housing strip 11, both step-shaped end sections of the strip 15 are formed complementary to one another, so that the ball pitch of the first ball row 17, the ball pitch of the second ball row 18 and the ball pitch of the third ball row 19 also remain substantially constant at the connection.FIG. 4 illustrates an enlarged plan view of the multi-row rolling element housing band 11. each second ball 18 ais displaced by P / 3 from each first ball 17 ain the longitudinal direction of the band 15 (more specifically, a single direction in the longitudinal direction, that is, the right direction in FIG. 4 ). P is the ball pitch of the first row of balls 17. likewise, each third ball 19a is displaced by P / 3 from each second ball 18a in the longitudinal direction of the belt 15. Therefore, as illustrated in a front view of FIG. 5, there are no balls 6 which completely overlap in the width direction, and the first ball 17 a, the second ball 18 a, and the third ball 19 aappear in the proper order in the longitudinal direction of the belt 15 in a cycle of P / 3.Each second ball 18a is longitudinally displaced from each first ball 17a. Each third ball 19a is displaced from each second ball 18a. Accordingly, the curl of the carriage 3 can be reduced. The reason for this will be described below. The ripple indicates that since the relative positions of the carriage 3 and the balls 6 change as the carriage 3 makes strokes, the number of effective balls and the balance of forces in the carriage 3 change with the change of the relative positions to cause a subtil displacement in the radial direction and a pitch direction inclination.FIG. 6 is a diagram explaining the principle of occurrence of waves. The reference numeral 2 denotes the guide rail, the reference numeral 3 the carriage, and the reference numerals 1 to 8 the balls which roll in the loaded path between the guide rail 2 and the carriage 3. St is the stroke number of the carriage 3. I is the number of effective balls. P is the ball pitch. An open arrow A1 is a load acting on the carriage 3. An arrow A2 is the displacement of the carriage 3 in the radial direction. An arrow A3 is the inclination of the carriage 3 in the inclination direction (clockwise). An arrow A4 is the inclination of the carriage 3 in the inclination direction (counterclockwise).S1 to S5 illustrate states in which the carriage 3 performs a right stroke. St to the right next to the carriage 3 represents the stroke number of the carriage 3. I represents the number of effective balls. The balls 1 to 8 also move to the right during rolling, with the movement of the carriage 3 to the right. The amount of movement of the balls 1 to 8 is half the amount of movement of the carriage 3.In S1 where St = 0, there are four balls on each of the left and right sides with respect to a center 3c of the carriage 3. Under the load are effective balls 2 to 4 and 5 to 7 which are equal in number, here three, left and right with respect to the center 3c of the carriage 3. Accordingly, the carriage 3 does not incline in the tilting direction. However, when the load is applied to the effective balls 2 to 7, the effective balls 2 to 7 are compressed and the carriage 3 is slid downward in the radial direction as indicated by the arrow A2. At each end portion of the carriage 3, a boss 3d is provided. The balls 1 and 8 are not under load.In S2 with St = 0.5 P, the effective balls 2 to 7 are under the load acting on the carriage 3 as in S1. Accordingly, the carriage 3 remains displaced downward in the radial direction. In S2, when the effective balls 5 to 7 on the left side with respect to the center 3c of the carriage 3 move slightly away from the center of the carriage 3 as compared with the effective balls 2 to 4 on the right side with respect to the center of the carriage 3, the moment balance is lost by the reaction force of the effective balls 2 to 7. The carriage 3 inclines slightly in the inclination direction (clockwise direction) as indicated by the arrow A3.In S3 with St=1.0 P, the ball 1 becomes the effective ball. The number of effective balls I becomes seven. The number of effective balls I is increased from six to seven. Accordingly, the downward movement of the carriage 3 in the radial direction is reduced as indicated by the arrow A2. There are the effective balls 1 to 7 symmetrically left and right with respect to the center 3c of the carriage 3.In S 4 with St=1.5 P, the ball 7 that was the effective ball becomes the ball 7 that is not under the load, and the number of effective balls I becomes six. Thus, the downward movement of the carriage 3 in the radial direction increases as compared with S3 as indicated by the arrow A2. At this time, the effective balls 1 to 3 move right with respect to the center 3c of the carriage 3 slightly away from the center of the carriage 3 as compared with the effective balls 4 to 6 left with respect to the center 3c of the carriage 3. The carriage 3 inclines slightly in the inclination direction (counterclockwise) as indicated by the arrow A4.In S5 of St = 2.0 P, the carriage 3 returns to the initial state of S1. In this way, the carriage 3 repeats a subtend displacement in the radial direction and inclines in the inclining direction in a cycle of 2 kDa.The more effective balls are provided, the smaller is a displacement in the radial direction and an inclination in the pitch direction of the carriage 3. for example, it is smaller when the number of effective balls changes from 18 to 19 than when the number of effective balls changes from six to seven. As in the embodiment, the three ball rows 17, 18 and 19 are arranged in the loaded path, each second ball 18a is displaced longitudinally of each first ball 17a, and each third ball 19a is displaced from each second ball 18a. Accordingly, it can be considered that the number of the eactive balls contributing to a reduction in the ripple has increased although the length of the loaded path C 1 is the same. Therefore, it is possible to promote a reduction in the ripple and hence an increase in the degree of precision of the guidance of the motion guidance device 1.In addition, when the number of the ball rows 17, 18 and 19 is three, each second ball 18a is displaced by P / 3 in the longitudinal direction of each first ball 17a, and each third ball 19a is displaced by P / 3 of each second ball 18a. Accordingly, the first ball 17 a, the second ball 18 a, and the third ball 19 aappear in the loaded path C 1 at the same pitch without overlapping each other, and enter the loaded path C 1 at the same pitch. Thereby, the ripple can be further reduced. Also, when the number of the ball rows is n, the ball rows are shifted by P / n to enable further reduction of the ripple.Moreover, the ball pitch of the first ball row 17, the ball pitch of the second ball row 18 and the ball pitch of the third ball row 19 are made equal. Accordingly, the first ball 17 a, the second ball 18 a, and the third ball 19 aappear in equal division without overlapping over the entire length of the loaded path C 1. Thereby, the ripple can be further reduced.The first ball row 17, the second ball row 18, and the third ball row 19 are arranged in the corresponding order in the width direction of the band 15. Accordingly, a distal end portion of the band 15 gradually bends from one end portion (a lower end portion of FIG. 4 ) to the other end portion (an upper end portion of FIG. 4 ) in the width direction in the U-shaped turning path C 3. Thus, the band 15 can be smoothly bent in the turning path C 3.The carriage 3 of the motion guide device 1 is provided with four loaded circulation paths C 1 for receiving loads in the up and down direction and in the left and right direction. The three ball rows 17, 18 and 19 are arranged in each loaded path C 1, and each of the balls 17 a, 18 aand 19 ais shifted as described above. Accordingly, it is possible to expect that many small-diameter balls are placed in each loaded path C 1, and to achieve the compatibility between increases in the degree of accuracy and the rigidity of the guide of the motion guide device 1.FIGS. 7A to 7F illustrate modifications of the multi-row rolling element housing band 11 of the first embodiment. In the first embodiment, as illustrated in FIG. 7A, the first to third ball rows 17, 18, and 19 are arranged in the order from one end portion (a lower end portion in FIG. 7A ) to the other end portion (an upper end portion in FIG. 7A ) of the multi-row rolling element housing tape 11 in the width direction. They may also be placed in the order of the first ball row 17, the third ball row 19 and the second ball row 18 as shown in FIG. 7B. They may also be placed in the order of the second ball row 18, the first ball row 17, and the third ball row 19 as illustrated in FIG. 7C. They may also be placed in the order of the third ball row 19, the first ball row 17, and the second ball row 18, as illustrated in FIG. 7D. They may also be placed in the order of the second ball row 18, the third ball row 19, and the first ball row 17 as shown in FIG. 7E. They may also be placed in the order of the third ball row 19, the second ball row 18, and the first ball row 17 as illustrated in FIG. 7F. In either case, each second ball 18a is longitudinally displaced by P / 3 from each first ball 17a, and each third ball 19a is longitudinally displaced by P / 3 from each second ball 18a. When distinguishing the front and back surfaces of the multi-row rolling element case band 11, the number of the placement patterns of the first to third ball rows 17, 18 and 19 is 3!. When the front and back sides of the multi-row rolling element case band 11 are not distinguished, the number of the placement patterns of the first to third ball rows 17, 18 and 19 is 3! / 2.(Multi-Row Roller Body Band of Second Embodiment)FIGS. 8A to 8D illustrate a multi-row rolling element housing band 31 of the second embodiment of the present invention. In the embodiment, as illustrated in FIG. 8A, four ball rows 33 to 36 are arranged in one band 32 of the multi-row rolling element housing band 31. The four ball rows 33 to 36 are the first ball row 33, the second ball row 34, the third ball row 35, and the fourth ball row 36 in the order from one end to the other end in the width direction. The adjacent ball rows 33 to 36 are all equally spaced from each other in the width direction. A spacer 37 is arranged between the balls of each of the ball rows 33 to 36. The ball pitch of each of the ball rows 33 to 36 is kept constant. Both end portions of the band 32 are formed in a stepped manner in four steps so as to complement each other.FIG. 9 illustrates an enlarged plan view of the multi-row rolling element housing band 31. each second ball 34 ais displaced by P / 4 in the longitudinal direction of the band 32 of each first ball 33 a. P is the ball pitch of the first ball row 33. likewise, each third ball 35a is displaced by P / 4 in the longitudinal direction of the band 32 of each second ball 34a, and each fourth ball 36a is displaced by P / 4 in the longitudinal direction of the band 32 of each third ball 35a. Therefore, as illustrated in FIG. 10, when viewed in the width direction, there are no entirely overlapping balls, and the first ball 33 a, the second ball 34 a, the third ball 35 a, and the fourth ball 36 aappear in the corresponding order in the longitudinal direction of the belt 32 in a cycle of P / 4. Accordingly, the number of effective balls can be increased to 4 / 3 times as compared with the three ball rows 17 to 19, and the ripple can be further reduced.FIG. 11 illustrates a modification of the multi-row rolling element housing band 31 of the second embodiment. The arrangement of the first to fourth ball rows 33 to 36 is not limited to the ball rows shown in FIG. 9. FIG. 11 illustrates an example in which the first ball row 33, the fourth ball row 36, the second ball row 34, and the third ball row 35 are placed from one end to the other end of the multi-row roller housing band 31 in the width direction. When distinguishing the front and back surfaces of the multi-row rolling element case band 31, the number of the placement patterns of the first to fourth ball rows 33 to 36 is 4!. When the front and back sides of the multi-row rolling element case band 31 are not distinguished, the number of the placement patterns of the first to fourth ball rows 33 to 36 is 4! / 2.(Motion Guide Device of Second Embodiment)FIG. 12 illustrates the motion guide device 41 of the second embodiment of the present invention. The basic structure of the motion guide device 41 of the second embodiment is the same as that of the motion guide device 1 of the first embodiment. Accordingly, the same reference numerals are assigned to them and their descriptions are omitted. The motion guidance device 41 of the second embodiment is also assigned a total of four circulation paths 4. The multi-row rolling element housing band 42 in which two ball rows are arranged is inserted into each circulation path 4.FIGS. 13A and 13B illustrate the multi-row rolling element housing band 42. The ball inclination of the first ball row 43 is kept constant. The spacer 45 is also disposed between the second balls 44 aof a second ball row 44. The ball pitch of the second ball row 44 is kept constant. The diameter of the first ball 43a is equal to the diameter of the second ball 44a. The ball pitch of the first ball row 43 is equal to the ball pitch of the second ball row 44.A band 46 is divided into three by two ball rows 43 and 44, i.e., a side band 47 protruding outward in the widthwise direction from the first ball row 43, a wavy middle band 48 between the first ball row 43 and the second ball row 44, and a side band 49 protruding outward in the widthwise direction from the second ball row 44. The first ball 43a and the second ball 44a are rendered non-contacting by the central band 48.Each second ball 44a is displaced by P / 2 in the longitudinal direction of the band 46 of each first ball 43a. P is the ball pitch of the first ball row 43, and as shown in FIG. 13B, there are no entirely overlapping balls as viewed in the width direction, and the first ball 43 aand the second ball 44 aappear in the longitudinal direction of the band 46 in a cycle of P / 2 in the order. In this manner, each second ball 44a is displaced longitudinally of the band 46 of each first ball 43a to enable reduction of wave motion.In addition, the spacer 45 is disposed between the first balls 43 a. The spacer 45 is disposed between the second balls 44 a. The first ball 43a and the second ball 44a are rendered non-contacting by the central band 48. Accordingly, the displacement amount of each second ball 44 aof each first ball 43 acan be kept constant, and also the first balls 43 aand the second balls 44 acan smoothly circulate.ExamplesAs shown in Figs. 14A to 14C, a ripple analysis of a case where three ball rows were arranged in a multi-row rolling element housing tape was performed. FIG. 14A illustrates a first comparative example when each first ball 17a', each second ball 18a', and each third ball 19a' were arranged side by side. In the case of the first comparative example, each first ball 17a', each second ball 18a', and each third ball 19a' completely overlap as viewed in the widthwise direction of a multi-row rolling element housing belt 11'. FIG. 14B illustrates a second comparative example in which each first ball 17a" and each second ball 18a" were longitudinally displaced by P / 2 and each second ball 18a" and each third ball 19a" were longitudinally displaced by P / 2. In this case, the position of each first ball 17a" in the longitudinal direction coincides with the position of each third ball 19a"in the longitudinal direction. FIG. 14C illustrates an example of the present invention in which each first ball 17 aand each second ball 18 aare longitudinally displaced by P / 3, and each second ball 18 aand each third ball 19 aare longitudinally displaced by P / 3.The analysis conditions are shown in Table 1. In the first comparative example, the second comparative example, and the present invention example, the analysis conditions were collectively set as shown in Table 1. [Table 1] Table 1] [Table 1] Table 1]First Comparative Example452,381158,1610,5150.25CSecond Comparative ExampleActual Invention ExampleFIGS. 15A and 15B are diagrams illustrating the results of analysis of the ripple in the radial direction and the pitch direction. The horizontal axis of the graph is a camber length. The wave values obtained by continuously changing the length of the bombardment were plotted.It was found that the wave value in the present invention example indicated by (c) in the graph could be reduced to about 1 / 7 as compared with the first comparative example indicated by (a) in the graph, and that the wave value could also be reduced to about 1 / 4 as compared with the second comparative example indicated by (b) in the graph. The wave value was reduced in the second comparative example compared to the first comparative example. Namely, in the second comparative example, each first ball 17a" and each second ball 18a" were displaced from each other, and it could be considered that the number of effective balls was doubled. In the present invention example, each first ball 17 a, each second ball 18 a, and each third ball 19 aare displaced from each other. Accordingly, it could be considered that the number of effective balls was tripled and the wave value could be further reduced to about 1 / 4 as compared with the second comparative example. The unit of the vertical axis of FIGS. 15A and 15B is nm. Revolutionary is to be able to eliminate the wave value largely in any bombardment length as in the present invention example.In the above embodiments, over the entire length of the multi-row rolling element housing band, each second ball is longitudinally displaced from each first ball and each third ball is longitudinally displaced from each second ball, but may be longitudinally displaced in a part of the multi-row rolling element housing band as described above. As above, when they are longitudinally shifted in a part of the multi-row rolling element housing band, even if the positions of the first to third balls in the other part of the multi-row rolling element housing band coincide in the longitudinal direction (e.g., an end portion of the multi-row rolling element housing band in the longitudinal direction or a center portion of the multi-row rolling element housing band in the longitudinal direction), the ripple of the slider 3 can be reduced.In the above embodiments, each second ball is displaced by P / n in the longitudinal direction of each first ball, and each third ball is displaced by P / n of each second ball. However, the amount of displacement is not limited thereto. As long as each second ball is displaced in the longitudinal direction of each first ball and each third ball is displaced in the longitudinal direction of each first ball and each second ball, the ripple of the carriage can be reduced.In the above embodiments, the diameter of the first ball, the diameter of the second ball, and the diameter of the third ball are the same, and the ball pitch of the first ball row, the ball pitch of the second ball row, and the ball pitch of the third ball row are the same. However, it is also possible to design at least one diameter of the first ball, the diameter of the second ball and the diameter of the third ball differently. In addition, it is also possible to design at least one of the ball pitch of the first ball row, the ball pitch of the second ball row and the ball pitch of the third ball row differently. When at least one of the ball pitches is different, it is desirable that the smallest common multiple of the ball pitch of the first ball row, the ball pitch of the second ball row, and the ball pitch of the third ball row is equal to or greater than the entire length of the multi-row rolling element housing band. Namely, the longitudinal positions of the first to third balls are prevented from being in some.In the above embodiments, the first ball, the second ball, the third ball appear in the order from one end to the other end of the ball cage in the longitudinal direction. However, it is also possible, for example, to eliminate the second ball at the left end of the multi-row rolling element housing band 11 of FIG. 3A, to place the second ball at the right end of the multi-row rolling element housing band 11, to eliminate the third ball at the left end of the multi-row rolling element housing band 11, and to place the third ball at the right end of the multi-row rolling element housing band 11. As a result, the slopes at the two step-shaped end portions of the band 15 become steeper, and it becomes easy to bend the band 15 in the U-shaped turning path C 3.In the above embodiments, the case of using balls as rolling elements has been described. However, a roller can also be used as a rolling element.List of reference characters1 Movement guide device 4 Circulation path 2 Guide rail 3 Slides 11, 31, 42 Multi-row rolling element housing strip 15, 32 Strip 17 to 19, 33 to 36 At least three ball rows (at least three rolling element rows) 17, 33 First ball row (first rolling element row) 18, 34 Second ball row (second rolling element row) 19, 35 Third ball row (third rolling element row) 20, 37 Spacer 36 Fourth ball row (fourth rolling element row) 17 a, 33 aof each first ball (each first rolling element) 18 a, 34 aof each second ball (each second rolling element) 19 a, 35 aeach third ball (each third rolling element) 36 aeach fourth ball (each fourth rolling element) P of first ball pitch (first rolling element pitch) 41 motion guide device 42 multi-row rolling element housing band 43 to 44 two ball rows (two rolling element rows) 43 first ball row (first rolling element row) 44 second ball row (second rolling element row) 43 aeach first ball (each first rolling element) 44 aeach second ball (each second rolling element) 45 spacer

Claims

A multi-row rolling element housing band, wherein at least three rolling element rows (17-19, 33-36) are arranged in a band (11, 31) and in at least a part of the band (11, 31) in a longitudinal direction thereof, second rolling elements (18a, 34a) of a second rolling element row (18, 34) are displaced by P / n in the longitudinal direction of the band (11, 31) from first rolling elements (17a, 33a) of a first rolling element row (17, 33), third rolling elements (19a, 35a) of a third rolling element row (19, 35) are displaced by P / n in the longitudinal direction from the second rolling elements (18a, 34a), the third rolling elements (19a, 35a) are displaced by 2P / n in the longitudinal direction from the first rolling elements (17a, 33a), a first to third opening portion row (15a, 15b, 15c) in which a plurality of the first rollers (17a, 33a), the first roller row (17, 33), a plurality of the second rollers (18a, 34a) of the second roller row (18, 34), and a plurality of the third rollers (19a, 35a) of the third roller row (19, 35) are accommodated are formed in a single band, and P is a roller pitch of the first to third roller rows (17-19, 33-35), and n is the number of the roller rows.The multi-row rolling element housing band according to claim 1, wherein the first rolling element row (17, 33), the second rolling element row (18, 34), and the third rolling element row (19, 35) are arranged in a width direction of the band (11, 31).The multi-row rolling element housing band according to any one of claims 1 or 2, wherein the number of the rolling element rows (17-19, 33-36) is three or four.A motion guide device comprising: a guide rail (2); a carriage (3) mounted on the guide rail (2) so as to be movable with respect to the guide rail (2); and the multi-row rolling element housing belt (11) according to any one of claims 1 to 3 integrated in a circulation path (4) of the carriage (3), wherein, as viewed from a front side of the carriage (3), in a state where the motion guide device (1) is disposed on a horizontal plane, the carriage (3) is provided with a total of four circulation paths (4), i.e., two upper and lower circulation paths on each of the left and right sides, and the multi-row rolling element housing belt (11) is integrated in each circulation path (4).A motion guide device comprising: a guide rail (2); a carriage (3) mounted on the guide rail (2) so as to be movable with respect to the guide rail (2); and a multi-row ball shroud (42) integrated into a circulation path (4) of the carriage (3), wherein, as viewed from a front side of the carriage (3), in a state where the motion guide device (41) is disposed on a horizontal plane, the carriage (3) is provided with four circulation paths (4) in total, i.e., two upper and lower circulation paths on each of left and right sides, the multi-row ball shroud (42) is integrated into each circulation path (4), two ball rows (43, 43, 44) in the multi-row rolling element housing band (42), and in at least a part of the multi-row rolling element housing band (42) in the longitudinal direction thereof, second balls (44a) of a second rolling element row (44) are shifted by about P / 2 in the longitudinal direction of the multi-row rolling element housing band (42) from first balls (43a) of a first ball row (43) in a state in which a spacer (45) is disposed between the first balls (43a), the spacer (45) is disposed between the second balls (44a), and the first and second balls (43a) are formed so as not to contact each other, first and second rows of opening portions in which a plurality of the first balls (43a) of the first ball row (43) and a plurality of the second balls (44a) of the second ball row (44) are accommodated, In a single multi-row ball shroud (42), the multi-row ball shroud (42) includes a side band (47) protruding widthwise outward from the first ball row (43), a corrugated middle band (48) between the first ball row (43) and the second ball row (44), and a side band (49) protruding widthwise outward from the second ball row (44) from the second ball row (44), the first ball (43a) and the second ball (44a) are rendered non-contact by the middle band (48), and P is a ball pitch of the first and second ball rows.The motion guide device according to claim 5, wherein both end portions of the multi-row ball housing belt (42) are formed stepwise in the longitudinal direction

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