Rolling guide device

Abstract

A linear guide (10) comprises: a guide rail (1) having a raceway groove (3) on a side surface; a slider (2) assembled to the guide rail (1) and having a raceway groove (7) facing the raceway groove (3); and a plurality of rolling elements disposed rollably in a rolling element rolling path (23), which is composed of a load rolling path (22) formed by the raceway grooves (3, 7), and a no-load rolling path (21) provided on the slider (2) and communicating between one end and the other end of the load rolling path (22). One of the guide rail (1) and the slider (2) moves relative to the other as the rolling elements roll. The plurality of rolling elements are constituted by a plurality of steel balls (6), and a plurality of spacer balls (16) smaller than the steel balls (6) and having elasticity. At least one spacer ball (16) is always present in the no-load rolling path (21). The length of a gap in which neither the steel balls (6) nor the spacer balls (16) are present in the rolling element rolling path (23) is 50% or less of the diameter of the steel balls (6), regardless of the position of the rolling elements. Consequently, it is possible to provide a rolling guide device that is easy to assemble and has good operability and excellent repeated positioning accuracy.

Description

Rolling guide device

[0001] The present invention relates to a rolling guide device used in measuring machines, machine tools, etc., for guiding a reciprocating object in the direction of movement.

[0002] Conventionally, a linear guide as a rolling guide device generally includes a guide rail with rail-side rolling grooves on its left and right side surfaces, a slider with slider-side rolling grooves provided at positions facing the rail-side rolling grooves of the guide rail, and a load-bearing rolling path formed by the rail-side rolling groove and the slider-side rolling groove, and a rolling element return path provided inside the slider, filled with a number of rolling elements that can roll in these rolling paths. End caps are attached to both axial ends of the slider, and direction-changing paths are formed inside the end caps for changing the direction of the rolling elements. The rolling elements roll in the rolling path consisting of the load-bearing rolling path, rolling element return path, and direction-changing path, thereby moving the slider relative to the guide rail in the axial direction. After changing direction inside the end caps, the rolling elements that roll in the rolling path return to their original positions through the rolling element return path formed inside the slider.

[0003] In such linear guides, the rotation directions of adjacent rolling elements in the loaded rolling path are opposite to each other, which can cause frictional forces at the contact points between the rolling elements to hinder smooth slider operation or cause the rolling elements to compete with each other. Furthermore, because the rolling element return path and direction change path are formed larger than the diameter of the rolling elements, the rolling elements in the rolling element return path and direction change path are pushed by the rolling elements in the loaded rolling path, causing competition between the rolling elements and reducing operability, just as in the loaded rolling path. Therefore, to improve the operability of rolling guide devices, various types of spacers have been disclosed that are arranged between adjacent rolling elements.

[0004] For example, Patent Document 1 describes a linear guide in which a cage is interposed between adjacent circulation balls. The cage has two concave ball receiving portions back to back, and a spacer ball with a smaller diameter than the circulation ball is rotatably held in the center of the ball receiving portion.

[0005] Patent Document 2 proposes a linear guide in which lubricant-containing polymer spacer balls are alternately interposed between steel balls. The lubricant-containing polymer spacer balls are slightly smaller than the steel balls to improve operability, and are molded from polyethylene consisting of low-molecular-weight polyethylene and ultra-high-molecular-weight polyethylene, with a lubricant impregnated therein.

[0006] Japanese Unexamined Patent Publication No. 2003-247619 Japanese Unexamined Patent Publication No. 8-170641

[0007] Incidentally, rolling guide devices used in the field of precision machinery such as measuring instruments require excellent repeatable positioning accuracy. Repeatable positioning accuracy refers to the variation in the position of a machine after each predetermined operation when the machine performs multiple predetermined operations. Specifically, in a linear guide, when the slider moves along the guide rail, the positions and number of contact points between the slider and the steel balls may change even if the slider is in the same position. For example, as shown in FIG. 9( a), the slider 2 is supported by five steel balls 6 before the predetermined operation. On the other hand, as shown in FIG. 9( b), when the slider 2 returns to its original position after the predetermined operation, it is supported by six steel balls 6.

[0008] In this way, if the number of contact points between the slider 2 and the steel ball 6 differs after a given operation, the repeatability of the positioning accuracy decreases. Specifically, after the operation shown in Figure 9(b), the measurement point 13 may be higher at the submicron level compared to before the operation shown in Figure 9(a). The position of the measurement point 13 also changes depending on the position of the contact point between the slider 2 and the steel ball 6. As shown in Figure 9(b), if the balance of the contact points is shifted to the right of the page, the slider 2 tilts counterclockwise, resulting in a shift in the measurement point 13.

[0009] During operation of the linear guide, the steel balls 6 move in a manner close to pure rolling, so in the load rolling path, the steel balls 6 roll in conjunction with the movement of the slider 2. However, the linear guide has a rolling element rolling path in which the steel balls 6 circulate endlessly, and in this rolling element rolling path there are gaps where no steel balls 6 are present. These gaps occur in multiple locations and move arbitrarily as the slider 2 moves. As a result, when the slider 2 is returned to its original position, the arrangement of the steel balls 6 does not return to its original position, and the attitude of the slider 2 changes.

[0010] The devices described in Patent Documents 1 and 2 do not take the above problems into consideration, and there is room for improvement before they can be applied to the field of precision machinery. Furthermore, in the linear guide described in Patent Document 1, the spacer balls must be held so that they do not simultaneously contact adjacent circulating balls under normal conditions, and the shape must be set so that adjacent circulating balls contact the spacer balls only when the ball receiving portion is deformed a predetermined amount by the pressing force of the circulating balls. Therefore, the design of the spacer becomes complicated, and the cage may collapse due to wear, resulting in a risk of malfunction.

[0011] Furthermore, when assembling the linear guide, the circulating balls and spacers must be inserted alternately into the slider, and the spacers must be positioned so that they are accurately held by the circulating balls on both sides, which reduces work efficiency during assembly.

[0012] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a rolling guide device that is easy to assemble, has good operability, and is excellent in repeatable positioning accuracy.

[0013] The above object of the present invention is achieved by the following configuration: (1) A rolling guide device comprising: a first member having a first raceway groove on a side surface; a second member assembled to the first member and having a second raceway groove facing the first raceway groove; a plurality of rolling elements packed in a rolling element rolling path comprising a loaded rolling path formed by the first raceway groove and the second raceway groove, and an unloaded rolling path provided in the second member and communicating one end of the loaded rolling path with the other, wherein the rolling elements cause one of the first member and the second member to move relative to the other as the rolling elements roll, the plurality of rolling elements being made up of a plurality of loaded balls and a plurality of elastic spacer balls smaller than the loaded balls, at least one spacer ball being present in the unloaded rolling path at all times, and the length of a gap in the rolling element rolling path where no loaded balls or spacer balls are present is 50% or less of the diameter of the loaded ball, regardless of the position of the rolling elements.

[0014] According to the rolling guide device of the present invention, load balls and spacer balls that are smaller than the load balls and have elasticity are filled into the rolling element rolling path, and the length of the gap within the rolling element rolling path where there are no spacer balls or load balls is appropriately adjusted, so that assembly work is easy, the device has good operability, and excellent repeatable positioning accuracy.

[0015] 1 is a perspective view showing a rolling guide device according to an embodiment of the present invention, with the rolling element rolling path partially cut away. It is a cross-sectional view schematically showing the rolling guide device shown in FIG. 1. It is a diagram schematically showing the III-III cross section in FIG. 2, illustrating a state in which steel balls and spacer balls are used and no ball filling gap S exists. It is a diagram corresponding to FIG. 3, illustrating a state in which only steel balls are used and the ball filling gap S exists. It is a schematic diagram for explaining the amount of steel balls entering and leaving the direction change path and the straight section communicating therewith. It is a graph showing the amount of entering and leaving accompanying the movement of the steel ball shown in FIG. 5, with the difference in the amount of entering and leaving on the vertical axis and the position of the steel ball used as a reference on the horizontal axis. It is a schematic diagram for explaining the amount of steel balls entering and leaving the direction change path of an actual rolling guide device and the straight section communicating therewith. It is a graph showing the amount of entering and leaving accompanying the movement of the steel ball shown in FIG. 7, with the difference in the amount of entering and leaving on the vertical axis and the position of the steel ball used as a reference on the horizontal axis. 5A and 5B are schematic diagrams showing the positional relationship between a slider and a steel ball in a rolling guide device, in which FIG. 5A shows the state before a predetermined operation, and FIG. 5B shows the state after the predetermined operation.

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rolling guide device according to an embodiment of the present invention will be described in detail below with reference to the drawings. In the present embodiment, a linear guide is exemplified as the rolling guide device.

[0017] 1 and 2 , a linear guide (rolling guide device) 10 includes a metal guide rail (first member) 1 that extends in one direction, and a slider (second member) 2 that has a generally C-shaped cross section and is assembled so as to straddle the guide rail 1 and is movable in the axial direction relative to the guide rail 1. In this specification, the front-to-rear direction refers to the direction in which the slider 2 moves along the guide rail 1, and the left-to-right direction refers to the width direction of the slider 2 attached to the guide rail 1.

[0018] Two axially extending upper and lower raceway grooves (first raceway grooves) 3 are formed on the left and right side surfaces of the guide rail 1. The slider 2 includes a slider body 9 having sleeve portions 4 on both the left and right sides of the guide rail 1, and a pair of end caps 5 attached to one end and the other end of the slider body 9 in the front-rear direction.

[0019] Two raceway grooves (second raceway grooves) 7, which face the raceway grooves 3 of the guide rail 1, are formed on each of the left and right sides of the inner surface of the sleeve portion 4 of the slider body 9. The opposing raceway grooves 3, 7 form two loaded rolling paths 22. The slider 2 is provided with an unloaded rolling path 21 that connects one end of the loaded rolling path 22 to the other end, and the loaded rolling path 22 and the unloaded rolling path 21 form a rolling element rolling path 23.

[0020] The end caps 5 are fixed to the front and rear ends of the slider body 9 by bolts 12. The end caps 5 are, for example, injection-molded products made of synthetic resin, and are formed with a generally U-shaped cross section similar to the slider body 9. The end caps 5, together with a return guide (not shown), constitute the direction change path of the unloaded rolling path 21.

[0021] As shown in Figure 3, a plurality of steel balls (load balls) 6 and a plurality of elastic spacer balls 16 are filled in a rollable manner within a total of four rolling element rolling paths 23 provided inside the slider 2. These steel balls 6 and elastic spacer balls 16 circulate while rolling within the rolling element rolling paths 23 in accordance with the relative movement between the guide rail 1 and the slider 2. The elastic spacer balls 16 are indicated by diagonal lines in the figure and will hereinafter be simply referred to as spacer balls or elastic spacer balls.

[0022] The elastic spacer balls 16 are smaller than the steel balls 6, for example, 95% of the diameter of the steel balls 6. The unloaded rolling path 21 is designed so that there is always at least one spacer ball 16. Furthermore, in this embodiment, the numbers of steel balls 6 and spacer balls 16 are determined so that when the rolling element rolling path 23 is filled with steel balls 6 and spacer balls 16, the length of the gap in the rolling element rolling path 23 where no steel balls 6 or spacer balls 16 are present is 50% or less, preferably 12% or less, of the diameter of the steel ball 6, regardless of the positions of the steel balls 6 and spacer balls 16.

[0023] In this embodiment, the ball filling gap S in the rolling element rolling path 23 is designed as follows to provide a structure with excellent repeatability in positioning accuracy. That is, the total length of the rolling element rolling path 23, which is made up of the loaded rolling path 22 and the unloaded rolling path 21, is not an integer multiple of the diameter of the steel balls 6, so as shown in FIG. 4 , when only steel balls 6 are filled in the rolling element rolling path 23, a ball filling gap S exists. The ball filling gap S refers to a gap in the rolling element rolling path where no rolling elements or the like are present. If the ball filling gap S is made small, competition between the steel balls 6 and the like is more likely to occur, so conventionally, the ball filling gap S has generally been set to approximately twice the diameter of the steel balls 6 or less.

[0024] The steel balls 6 in the unloaded rolling path 21 do not move unless pushed by the steel balls 6 in the loaded rolling path 22, so the steel balls 6 are always packed tightly within the unloaded rolling path 21. As shown in FIG. 4 , when the steel balls 6 in the loaded rolling path 22 move in the direction of arrow 11 as the slider 2 moves, the ball filling gap S also appears to move in the direction of arrow 11. However, if the steel balls 6 move in the direction opposite to arrow 11 from the state shown in FIG. 4 , a new ball filling gap S is generated at position A and then moves in accordance with the movement of the steel balls 6. Because the steel balls 6 are not constrained within the unloaded rolling path 21, they may be affected by gravity or, if they move quickly, may move due to inertia caused by the kinetic energy of the steel balls 6 themselves, resulting in gaps being generated in multiple locations. For this reason, the position of the ball filling gap S is difficult to predict due to various factors such as the movement method and mounting posture of the slider 2. As a result, the repeatability of positioning accuracy decreases, as described above.

[0025] The inventors of the present application have conducted various studies on methods for adjusting the ball packing gap S in the rolling element rolling path 23. For example, if the overall length of the rolling element rolling path 23 is to be adjusted in order to adjust the ball packing gap S, it is necessary to adjust the length of the slider 2 or change the end cap 5, which is a large-scale and difficult task. Furthermore, if the ball packing gap S is made too small, friction fluctuations increase due to the effects of competition between the steel balls 6 and fluctuations in the overall length of the rolling element rolling path 23, and the operability of the slider 2 decreases.

[0026] Therefore, in this embodiment, the ball filling gap S is narrowed by inserting a plurality of spacer balls 16 into the rolling element rolling path 23. That is, by using spacer balls 16 that are smaller than the steel balls 6, the ball filling gap S can be adjusted. As a result, the change in the posture of the slider 2 before and after a predetermined operation is reduced, and repeatable positioning accuracy can be improved.

[0027] For example, if the ball packing gap S when steel balls 6 are packed into the rolling element rolling paths (i.e., before adjustment) is 0.8 of the diameter Dw of the steel balls 6, then as shown in Figure 3, by removing three steel balls 6 and inserting four spacer balls 16 each having a diameter that is 95% of the diameter of the steel balls 6, the ball packing gap S can be made 0. The following formula can be used to make the ball packing gap S 0.

[0028] [Total length of ball filling gap S and three steel balls 6 before adjustment] 0.8Dw + 3Dw = 3.8Dw (mm) [Total length of four spacer balls 16] 0.95Dw x 4 = 3.8Dw (mm) As described above, the total length of ball filling gap S and three steel balls 6 is equal to the total length of four spacer balls 16, so the ball filling gap S can be set to 0.

[0029] The number of spacer balls 16 is two or more, but if the number of spacer balls 16 is too large, the load capacity will decrease, so it is preferable that the number of spacer balls 16 is less than the number of steel balls 6.

[0030] As described above, generally, if the rolling element rolling path 23 is filled only with steel balls 6 and the ball packing gap S is made too small, the steel balls 6 tend to compete with each other, increasing friction fluctuations and reducing the operability of the slider 2. However, in this embodiment, multiple spacer balls 16 are inserted into the rolling element rolling path 23, and the elasticity of the spacer balls 16 can mitigate the competition between the steel balls 6, thereby preventing a reduction in the operability of the slider 2. Note that, within the range of the elasticity of the spacer balls 16, it is also possible to adjust the total length of the four spacer balls 16 so that it is greater than the total length of the ball packing gap S and the three steel balls 6 before adjustment. In this case, the calculated ball packing gap S after adjustment becomes negative, and the spacer balls 16 are pressed by the steel balls 6 on both sides and circulate in the rolling element rolling path 23 in a slightly deformed state.

[0031] 3, at least one spacer ball 16 is always present in the unloaded rolling path 21. By always disposing the spacer ball 16 in the unloaded rolling path 21, it is possible to obtain the effect of absorbing the competition between the steel balls 6 in the unloaded rolling path 21.

[0032] Furthermore, it is preferable that the plurality of spacer balls 16 are arranged at approximately equal intervals between the steel balls 6. This ensures that at least one spacer ball 16 is arranged in the unloaded rolling path 21, and that approximately the same number of spacer balls 16 are always arranged in the loaded rolling path 22, thereby preventing a decrease in positioning accuracy. Note that "approximately equal intervals" means that the number of steel balls 6 between adjacent spacer balls 16 is n or n+1 (n is any integer).

[0033] When the steel ball 6 moves within the rolling element rolling path 23, a movement fluctuation occurs that causes the ball filling gap S to fluctuate. The magnitude of this movement fluctuation varies depending on the arc radius R of the direction change path (arc portion 17) of the linear guide and the size of the step D between the arc portion 17 and the straight portion 18. This will be described in detail below using FIGS. 5 to 8. Note that FIG. 5 shows the case where the steel balls 6a to 6e move within a path consisting of the arc portion 17 and the straight portion 18, and this path has a cross-sectional diameter identical to the diameter of the steel balls 6a to 6e. Furthermore, within the arc portion 17, the centers of the steel balls 6a to 6e are located on the arc radius R. Furthermore, in FIG. 5, X1 indicates the distance from the boundary between the arc portion 17 and the straight portion 18 to the center of the steel ball 6a, and X2 indicates the distance from the boundary to the center of the steel ball 6e. As shown in Figure 5, even if steel ball 6e moves in the direction of arrow 19 and the arrangement of steel balls 6a to 6e changes, X1 increases by the amount that X2 decreases, so X1 + X2 always appears to be the same value. However, if there is an arc in the movement path of the steel ball, X1 + X2 actually changes, albeit slightly.

[0034] FIG. 6 shows the variation in the amount of movement when the arc radius R of the arc portion 17 is 3.5 mm, 4 mm, and 5 mm and the steel ball 6e moves in the direction of arrow 19 by the diameter of the steel ball (4.7 mm). Note that in FIG. 6, the initial value of X1 + X2 shown in FIG. 5 is set to 0. As shown in FIG. 6, the smaller the arc radius R indicating the center of the arc portion 17, the greater the variation in the amount of movement. When the arc radius R is 3.5 mm (approximately 74% of the diameter of the steel ball), i.e., a value that is also applied to actual product linear guides, the variation in the amount of movement of X1 + X2 is approximately 0.11 mm, as shown in FIG. 6. Since actual linear guides have arc portions at both ends of the slider, taking into account the two arc portions, the variation in the amount of movement is 0.22 mm, which is approximately 4.6% of the diameter of the steel ball.

[0035] Furthermore, in an actual linear guide, as shown in Figure 7, the cross section of the unloaded rolling path 21 in a direction perpendicular to the direction of travel of the steel ball is set larger than the diameter of the steel ball, for example, 1.1 times the diameter of the steel ball. When the steel balls 6a-6e move in the direction of arrow 19 within such a rolling element rolling path 23, the steel balls 6a-6e move along the outer wall of the arc portion 17, so the centers of the steel balls 6a-6e move outside the arc radius R of the arc portion shown in Figure 5, and a deviation (step D) in the center position of the steel balls is formed between the arc portion 17 and the straight portion 18. In reality, since both the arc portion 17 and the straight portion 18 on the unloaded rolling path 21 side are unloaded rolling paths, the apparent step is zero. However, since the position of the steel ball within the straight portion 18 is not limited to the outside, the steel ball 6a is positioned in the center of the straight portion 18 in the figure. In this way, when a steel ball moves from a loaded rolling path to an unloaded rolling path, or from an unloaded rolling path to a loaded rolling path, a fluctuation in the amount of movement occurs that is greater than the amount of movement shown in FIG.

[0036] FIG. 8 shows the fluctuation in the amount of movement when the step D is set to 0 mm, 0.1 mm, and 0.2 mm and the steel ball 6e moves in the direction of arrow 19 by the diameter of the steel ball. In FIG. 8, the diameter of the steel ball is assumed to be 4.7625 mm, and the unloaded rolling path has a cross-sectional diameter 1.1 times this diameter. As shown in FIG. 8, the larger the step D, the greater the fluctuation in the amount of movement. That is, when the step D is 0.2 mm, the fluctuation in the amount of movement (X1 + X2) is approximately 0.27 mm. As in the case shown in FIG. 6, when the step D at both ends of the slider is taken into account, the fluctuation in the amount of movement is approximately 0.54 mm, which is approximately 12% of the diameter of the steel ball. In FIG. 8, the portion where the amount of movement fluctuates significantly occurs when the steel ball passes over step D.

[0037] As described above, if the rolling element rolling path 23 is filled with steel balls without any gaps, the fluctuation in the amount of movement will be large, significantly deteriorating the operating characteristics of the linear guide. However, in this embodiment, as shown in FIG. 4, the ball filling gap S is set to zero by inserting elastic spacer balls 16, thereby improving repeatability and positioning accuracy while maintaining operability. The effect of improving operating characteristics by the spacer balls 16 is most pronounced when the ball filling gap S in the rolling element rolling path 23 is 12% or less of the diameter of the steel balls. This is consistent with the value obtained from the fluctuation in the amount of movement described above, assuming that the step D is 0.2 mm. Therefore, in the present invention, the length of the gap (ball filling gap) in the rolling element rolling path where no loaded balls or spacer balls exist is set to 50% or less, preferably 12% or less, of the diameter of the loaded ball, regardless of the position of the rolling element.

[0038] In this embodiment, the spacer balls 16 are not particularly limited in terms of material, etc., as long as they have elasticity, but in consideration of elasticity, durability, etc., they are preferably one type selected from synthetic rubber (such as acrylic rubber), resin (such as polyacetal), and thermoplastic elastomer. Alternatively, spacer balls that have been given elasticity by devising a shape may be used.

[0039] The diameter of the elastic spacer balls is preferably about 95% (for example, 95%±1%) of the diameter of the load balls. In the above embodiment, the case where spacer balls 16 having a diameter that is 95% of the diameter of steel balls 6 is described. However, for example, for multiple types of steel balls frequently used in linear guides, it is also possible to prepare spacer balls having a diameter that is 95% of each steel ball, and use spacer balls of various sizes.

[0040] On the other hand, the diameter of the elastic spacer balls is preferably 75% or more of the diameter of the load balls. For example, in a linear guide using steel balls with a diameter of 3 / 16 inch (4.7625 mm), spacer balls (3.77 mm) prepared for steel balls with a diameter of 5 / 32 inch (3.9688 mm) are suitable because their diameter is 79.1% of the diameter of the steel balls. In this way, by using spacer balls with various diameters, it is possible to efficiently adjust the ball packing gap to a small size. Also, as mentioned above, depending on the application of the rolling guide device, even if the ball packing gap is set to 0 or less (a state in which the spacer balls are slightly crushed), the elasticity of the spacer balls allows them to be used.

[0041] The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit and scope of the present invention. For example, in the above embodiment, steel balls 6 are used as load balls, but the load balls are not limited to being made of metal, and ceramic balls or the like may also be used. Furthermore, in the above embodiment, a linear guide is used as an example of a rolling guide device, but the present invention can also be applied to a ball screw.

[0042] As described above, the present specification discloses the following: (1) A rolling guide device comprising: a first member having a first raceway groove on a side surface; a second member assembled to the first member and having a second raceway groove facing the first raceway groove; a plurality of rolling elements filled in a rolling element rolling path that is configured so as to be able to roll, the rolling elements comprising a loaded rolling path formed by the first raceway groove and the second raceway groove, and an unloaded rolling path provided in the second member and communicating one end of the loaded rolling path with the other; wherein the rolling elements cause one of the first member and the second member to move relative to the other as the rolling elements roll, wherein the plurality of rolling elements are constituted by a plurality of loaded balls and a plurality of elastic spacer balls that are smaller than the load balls, at least one spacer ball is always present in the unloaded rolling path, and the length of a gap in the rolling element rolling path where there are no loaded balls or spacer balls is 50% or less of the diameter of the loaded ball, regardless of the position of the rolling elements. This structure allows for easy assembly, has good operability, and provides excellent repeatable positioning accuracy.

[0043] (2) The rolling guide device according to (1), wherein the spacer balls are made of one material selected from the group consisting of synthetic rubber, resin, and thermoplastic elastomer. With this configuration, the spacer balls can be configured to have both elasticity and durability.

[0044] (3) The rolling guide device according to (1) or (2), wherein the diameter of the spacer balls is 75 to 95% of the diameter of the load balls. With this configuration, the ball packing gap can be efficiently adjusted to a small size.

[0045] (4) The rolling guide device according to any one of (1) to (3), wherein the number of the spacer balls is smaller than the number of the load balls. With this configuration, it is possible to narrow the ball packing gap while suppressing a decrease in load capacity.

[0046] (5) The rolling guide device according to any one of (1) to (4), wherein the plurality of spacer balls are arranged at approximately equal intervals between the loaded balls. With this configuration, the probability that the spacer balls are arranged in the loaded rolling path is high, and friction between the loaded balls can be suppressed, thereby reducing jostling between the loaded balls.

[0047] This application is based on a Japanese patent application (Patent Application No. 2024-51760) filed on March 27, 2024, the contents of which are incorporated herein by reference.

[0048] DESCRIPTION OF SYMBOLS 1 Guide rail (first member) 2 Slider (second member) 3 Raceway groove (first raceway groove) 4 Sleeve portion 5 End cap 6, 6a, 6b, 6c, 6d, 6e Steel ball (loaded ball) 7 Raceway groove (second raceway groove) 9 Slider body 10 Linear guide (rolling guide device) 13 Measurement point 16 Spacer ball 17 Arc portion 18 Straight portion 21 Unloaded rolling path 22 Loaded rolling path 23 Rolling body rolling path S Ball filling gap

Claims

1. A rolling guide device comprising: a first member having a first raceway groove on its side; a second member assembled to said first member and having a second raceway groove facing said first raceway groove; a plurality of rolling elements packed in a rolling element rolling path comprising a loaded rolling path formed by said first raceway groove and said second raceway groove; and an unloaded rolling path provided in said second member and connecting one end of said loaded rolling path to the other, said rolling elements causing one of the first member and the second member to move relative to the other as said rolling elements roll; said plurality of rolling elements comprising a plurality of loaded balls and a plurality of elastic spacer balls smaller than said loaded balls; at least one spacer ball always present in said unloaded rolling path; and the length of a gap in said rolling element rolling path where there are no loaded balls or spacer balls is 50% or less of the diameter of said loaded ball, regardless of the position of said rolling elements.

2. The rolling guide device according to claim 1, wherein the spacer balls are made of one material selected from the group consisting of synthetic rubber, resin, and thermoplastic elastomer.

3. A rolling guide device according to claim 1 or 2, wherein the diameter of the spacer balls is 75 to 95% of the diameter of the load balls.

4. A rolling guide device according to any one of claims 1 to 3, wherein the number of the spacer balls is less than the number of the load balls.

5. A rolling guide device according to any one of claims 1 to 4, wherein the plurality of spacer balls are arranged at approximately equal intervals between the load balls.

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