JP7798549B2 - Linear guide unit - Google Patents

Description

The present invention relates to a linear motion guide unit.

A known linear motion guide unit is one that includes a rail, a table, and rolling elements held in a cage. When the table reciprocates along the rail, the rolling elements reciprocate within a linear track formed between the rail and the table. This type of linear motion guide unit is generally referred to as a finite linear motion guide unit. With a finite linear motion guide unit, misalignment can occur in the relative positions of the rail, table, and cage as the unit repeatedly reciprocates.

A known finite linear motion guide unit includes a track (the rail and table are collectively referred to as the track), a cage that holds the rolling elements, and a displacement prevention mechanism that prevents displacement between the track and the cage (Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2004-197850 Japanese Patent Application Publication No. 1-154422

It is desirable for finite linear motion guide units to be able to prevent misalignment and have a simple structure yet high rigidity. Therefore, one of the objectives is to provide a finite linear motion guide unit that is able to prevent misalignment and has a simple structure yet high rigidity.

A linear motion guide unit according to the present disclosure comprises a rail having a pair of first raceway grooves on its side surface; a table having a pair of second raceway grooves facing the first raceway grooves; a plurality of rolling elements incorporated into the raceway formed by the first raceway grooves and the second raceway grooves and rolling as the table moves; and a cage that rotatably holds the rolling elements and moves along the rail as the rolling elements roll. The linear motion guide unit also includes a pair of rack gears fixed to the rail and the table, respectively, and a pinion gear rotatably mounted to the cage and meshing with the pair of rack gears. The outer surface of the rail includes a first outer surface portion that is continuous with the bottom surface of the rail via a curved surface, and a second outer surface portion that is an end surface extending in the thickness direction of the steel plate that constitutes the rail.

The linear guide unit described above prevents misalignment and provides a simple structure with high rigidity.

FIG. 1 is a plan view showing the structure of a linear motion guide unit according to the first embodiment. FIG. 2 is a perspective view showing the internal structure of the linear guide unit 1 with the components shifted. FIG. 3 is an exploded perspective view showing the linear motion guide unit 1. As shown in FIG. FIG. 4 is a perspective view showing the cage 4 and the pinion gear 6 taken out from the linear motion guide unit 1. As shown in FIG. FIG. 5 is an enlarged plan view showing the hole 45 of the cage 4 and the pinion gear 6. As shown in FIG. FIG. 6 is a perspective view showing the rail 2 and the rack gear 51 taken out from the linear motion guide unit 1. As shown in FIG. FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. FIG. 8 is a perspective view showing the rail 2. As shown in FIG. FIG. 9 is a perspective view showing a modified example of the rail in the linear motion guide unit according to the present disclosure. FIG. 10 is a perspective view showing a modified example of the rail in the linear guide unit according to the present disclosure. FIG. 11 is a perspective view showing a portion of the configuration of a linear motion guide unit 11, which is a modified example of the linear motion guide unit 1. As shown in FIG.

[Outline of the embodiment]
First, embodiments of the present disclosure will be listed and described.

A linear motion guide unit according to the present disclosure comprises a rail having a pair of first raceway grooves on its side surface; a table having a pair of second raceway grooves facing the first raceway grooves; a plurality of rolling elements incorporated into the raceway formed by the first raceway grooves and the second raceway grooves and rolling as the table moves; and a cage that rotatably holds the rolling elements and moves along the rail as the rolling elements roll. The linear motion guide unit also includes a pair of rack gears fixed to the rail and the table, respectively, and a pinion gear rotatably mounted to the cage and meshing with the pair of rack gears. The outer surface of the rail includes a first outer surface portion that is continuous with the bottom surface of the rail via a curved surface, and a second outer surface portion that is an end surface extending in the thickness direction of the steel plate that constitutes the rail.

In a conventional finite linear guide unit, rack gears are attached to both the rail and the table, and a pinion gear that meshes with the rack gear is attached to the cage to prevent misalignment of the cage. For example, Patent Document 1 discloses a misalignment prevention mechanism that includes a rack gear attached to a track, a holder that is elastically held in a hole in the cage, and a pinion gear that is rotatably supported by the holder. Furthermore, the finite linear guide unit shown in Patent Document 2 also has a rack gear and a pinion gear. In the finite linear guide unit of Patent Document 2, the cage has a thick central widthwise portion, and a bearing portion is formed in the central portion, which supports the rotational axis of the pinion gear.

The slippage prevention mechanism in Patent Document 1 avoids an increase in height by providing grooves in both the rail and the table and attaching a rack gear inside the grooves. However, the cost incurred in machining the grooves may be undesirable. On the other hand, the finite linear motion guide unit in Patent Document 2 uses rails formed by bending steel plate. While bent rails have a simple structure and are preferable from a cost perspective, they may not be sufficiently rigid. Such bent rails are also commonly referred to as pressed rails.

When trying to ensure rigidity in press-formed rails, one option is to use thicker steel plates. However, when thicker steel plates are bent, the curved portion between the bottom and side surfaces of the rail inevitably becomes larger, reducing the flat surface on the side of the rail. For this reason, if the side of the rail is to be used as a reference surface (the surface that serves as a reference when installing a linear motion guide unit), the rail must be made taller, making it difficult to meet the demand for miniaturization.

In contrast, the linear motion guide unit of the present disclosure is equipped with a slippage prevention mechanism that includes a rack gear and pinion gear. Furthermore, the outer surface of the rail includes a first outer surface portion that is connected to the bottom surface of the rail via a curved surface, and a second outer surface portion that is an end surface extending in the thickness direction of the steel plate that constitutes the rail. In other words, a portion of the outer surface of the rail is composed of an end surface that extends in the thickness direction of the steel plate that constitutes the rail. As a result, even if the rail is a pressed rail and the steel plate that constitutes the rail is thick, it is possible to ensure a flat portion on the rail side while keeping the rail height low. With this configuration, it is possible to construct a compact pressed rail using thick steel plate, while still having a reference surface on the outer surface. As such, according to the present disclosure, a compact finite linear motion guide unit can be realized while ensuring low cost and rigidity.

The rail may include a bottom wall and a pair of side walls rising from both longitudinal ends of the bottom wall. The bottom wall may include a first bottom wall portion connected to the side wall portion via a curved portion between the bottom wall and the side wall portion, a second bottom wall portion wider than the first bottom wall portion and extending across the entire width of the rail, and a third bottom wall portion located between the first and second bottom wall portions. Such a rail can be produced using a reasonably cost-effective, industrially feasible method of pressing a steel plate with a cutout or notch in one portion to bend it. This allows for the production of a small, finite linear motion guide unit with sufficient rigidity at low cost.

The rail may be constructed from a single steel plate. The rail may be a so-called pressed rail. By using a pressed rail, a limited linear motion guide unit can be provided at a reasonable cost.

The outer surface of the rail may include a reference portion that is exposed and not covered by the table regardless of the position of the table, and this reference portion may be used as the reference surface of the linear motion guide unit. This configuration makes it possible to provide a finite linear motion guide unit that uses press-formed rails, is highly rigid, and allows the rail side surface to be used as a reference surface.

The cage may be constructed from a single steel plate, and the pinion gear shaft may be held directly in a hole formed in the cage. This configuration prevents misalignment and reduces the number of parts, providing a linear guide unit with a simple configuration.

The hole formed in the retainer includes a first hole portion through which the pinion gear tooth rotates, and a second hole portion that rotatably holds the pinion gear shaft, and the width of the second hole portion may be 0.1 mm to 0.2 mm larger than the diameter of the pinion gear shaft. By setting the relationship between the diameter of the pinion gear shaft and the width of the second hole portion that holds the shaft within this range, the pinion gear will not come off the retainer and will be rotatably held, achieving a simple slippage prevention mechanism without using a holder.

[Specific Example of the Embodiment]
Next, an example of a specific embodiment of the linear guide unit of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
Fig. 1 is a plan view showing the structure of a linear motion guide unit 1, which is a linear motion guide unit according to an embodiment of the present disclosure. Fig. 2 is a perspective view showing the internal structure of the linear motion guide unit 1 with the members of the linear motion guide unit 1 shifted. Fig. 3 is an exploded perspective view showing the linear motion guide unit 1 in an exploded state.

Referring to Figures 1 and 2, the linear guide unit 1 comprises a rail 2, a table 3, a cage 4, rack gears 51 and 52, a pinion gear 6, and rolling elements 7. The table 3 is slidable along the rail 2 via the rolling elements 7. The table 3 includes a table body 31 and end plates 32 attached to both longitudinal end surfaces of the table body 31. The end plates 32 are fixed to the table body 31 by screws 101. When the linear guide unit 1 is viewed in the longitudinal direction (i.e., the state shown in Figure 1), a portion of the end plate 32 is positioned so as to overlap a portion of the cage 4 and the rolling elements 7. The end plates 32 function as stoppers for the rolling elements 7 and cage 4 to prevent the rolling elements 7 and cage 4 from falling off the rail 2 and table 3.

The table body 31 has a top surface 311 and sleeve portions 312 hanging down from both widthwise ends of the top surface 311. The inner surface 312a of the sleeve portion 312 faces the upper portion of the outer surface 2a of the rail 2. The lower portion 2s of the outer surface 2a of the rail 2 is not covered by the table 3. The top surface 311 is provided with a hole 33 used for attaching external equipment and a hole 34 used for attaching the rack gear 52.

Referring to Figures 2 and 3, a pair of first raceway grooves 21 are formed on both side surfaces of the rail 2. Furthermore, a second raceway groove 81 is formed in each of the sleeve portions 312 on both sides of the table body 31, facing the respective first raceway groove 21. The opposing first raceway grooves 21 and second raceway grooves 81 form a raceway. The raceway is a linear duct that runs along the longitudinal direction of the rail 2 and the table body 31. A plurality of rolling elements 7, which are balls, are inserted into the raceway. The rolling elements 7 are spaced apart from one another and are rotatably held in windows 41 of the cage 4. Note that for ease of understanding, Figure 2 shows the cage 4 and rolling elements 7 pulled out from the table 3; however, in reality, the presence of end plates 32 prevents the cage 4 and rolling elements 7 from being pulled out beyond the end plates 32.

The entire retainer 4 is constructed from a single bent steel plate. The retainer 4 includes a pair of retaining plate portions 42 and a connecting portion 43 that connects the retaining plate portions 42. The retaining plate portions 42 extend parallel to the outer surface 2a of the rail 2 and the inner surface 312a of the table body 31. The retaining plate portions 42 are provided with multiple circular windows 41. The connecting portion 43 includes a pair of first portions 43a that extend along the upper end surface of the rail 2, a second portion 43b that is parallel to the inner bottom surface 2b of the rail 2, and a pair of third portions 43c that are slopes that connect the first portion 43a and the second portion 43b.

Referring to Figures 1 and 3, a rack gear 51 extending in the longitudinal direction is attached to the center of the width of the inner bottom surface 2b of the rail 2. A rack gear 52 extending in the longitudinal direction is attached to the center of the width of the table body 31. The rack gears 51 and 52 are positioned opposite each other. A pinion gear 6 that meshes with the rack gears 51 and 52 is positioned between the rack gears 51 and 52. The pinion gear 6 is rotatably held in the cage 4.

When the table 3 moves due to an external force, the rolling elements 7 slide and rotate on the first raceway grooves 21 and second raceway grooves 81, and move along the rail 2 together with the cage 4. The longitudinal lengths of the rail 2 and the table body 31 are approximately equal. The longitudinal length of the cage 4 is approximately 2/5 to 3/5 of the longitudinal lengths of the rail 2 and the table body 31.

Figure 4 is a perspective view showing the cage 4 and pinion gear 6 removed from the linear guide unit 1. An enlarged view of the area enclosed by the two-dot chain line is also shown. The entire cage 4 is made of a single steel plate of a certain thickness, bent, for example, by press working. There are no particular restrictions on the thickness of the steel plate that makes up the cage 4, but a stainless steel plate with a thickness of approximately 0.5 mm to 1 mm can be used, for example. As mentioned above, the cage 4 has a retaining plate portion 42 that is parallel to each side of the rail 2. The retaining plate portion 42 has multiple parallel windows 41 (seven in the example shown in Figure 4) that can rotatably hold the rolling elements 7.

The pair of holding plate portions 42 are connected via a connecting portion 43. The connecting portion 43 includes a first portion 43a adjacent to the holding plate portion 42. The first portion 43a is located between the lower surface of the top surface portion 311 (Figure 3) of the table body 31 and the upper end surface of the rail 2, is parallel to these surfaces, and is set at a height that is spaced apart from both. A second portion 43b extending longitudinally is located at the center of the width of the connecting portion 43. The second portion 43b is parallel to the first portion 43a. The second portion 43b is positioned equidistant in the height direction from both rack gears 51 and 52 (Figure 1). A hole 45 is formed in the longitudinal center of the second portion 43b. The pinion gear 6 is directly held in the hole 45. "Directly held" means that there are no separate members such as holders or bearings between the cage and the pinion gear, and the pinion gear is maintained in a predetermined position in such a way that the cage and pinion gear can come into direct contact with each other.

FIG. 5 is an enlarged plan view of the hole 45 of the cage 4 and the pinion gear 6. Referring to FIGS. 1, 4, and 5, the pinion gear 6 includes a gear portion 61 and a rotating shaft 62. The rotating shaft 62 protrudes to both sides from the center of the gear portion 61. The thickness of the rotating shaft 62, i.e., the diameter _t2 ( _W2 ) of the rotating shaft 62, is greater than the thickness _t1 of the steel plate that constitutes the cage 4. The relationship between _t1 and _t2 is not particularly limited as long as the pinion gear is held without coming off the cage during operation of the linear motion guide unit. For example, _t2 can be approximately 2 to 2.5 times _t1 . Furthermore, the relationship between _t1 and _t2 is not limited to _t2 > _t1 , and may be _t2 ≦ _t1 .

Referring to FIG. 5 , the hole 45 formed in the cage 4 is a cross-shaped hole including a first hole portion 451 extending in the longitudinal direction of the cage 4 and a second hole portion 452 extending in the width direction of the cage 4. The first hole portion 451 is sized so that the gear portion 61 does not come into contact with the peripheral wall defining the first hole portion 451, allowing the pinion gear 6 to rotate freely. For example, the width _W3 of the first hole portion 451 can be approximately 0.3 mm larger than the width _W4 of the gear portion 61. The second hole portion 452 rotatably holds the rotation shaft 62 of the pinion gear 6. The width _W1 of the second hole portion 452 is preferably slightly larger than the diameter _W2 ( _t2 ) of the pinion gear 6. The width _W1 of the second hole portion 452 is preferably 0.1 mm to 0.2 mm larger than the diameter _W2 ( _t2 ) of the pinion gear 6. Within this range, the pinion gear 6 will not come off the cage 4 and can rotate freely. Therefore, the pinion gear 6 will not interfere with the operation of the table 3.

Figure 6 is a perspective view showing the rail 2 and rack gear 51 removed from the linear guide unit 1. Figure 7 is a cross-sectional view taken along line VII-VII in Figure 6. Figure 8 is a perspective view mainly showing the bottom wall portion 27 of the rail 2. Referring to Figures 6 and 7, the entire rail 2 is constructed from a single bent steel plate. The rail 2 is a so-called pressed rail. The rail 2 includes the bottom wall portion 27, a pair of side wall portions 28 rising from both longitudinal ends of the bottom wall portion 27, and a curved portion 29 located between the bottom wall portion 27 and the side wall portion 28. The upper portion of the side wall portion 28 is a wall that continues in the longitudinal direction. A first track groove 21 is formed on the outer surface 2a of the side wall portion 28. Meanwhile, a portion of the lower portion of the side wall portion 28 forms a notch 22. A portion of the bottom wall portion 27 extends to reach the notch 22. The end surface 272b of the extending bottom wall portion 27 forms part of the outer surface 2a of the rail 2.

In other words, the outer surface 2a of the rail 2 comprises two portions: a first outer surface portion 28a and a second outer surface portion 272b. Referring to Figures 6 to 8, the first outer surface portion 28a is connected to the bottom surface 27a of the bottom wall portion 27 via a curved portion 29a. The second outer surface portion 272b is the end face of the second portion 272 of the bottom wall portion 27, and is the end face 272b that extends in the thickness direction of the steel plate that makes up the rail 2. The effects of a rail with this shape will be explained next.

Conventionally, finite linear guide units have a surface (reference surface) that serves as a reference when installing the linear guide unit. The exposed portion of the rail's outer surface that does not overlap with the table has sometimes been used as the reference surface. The surface used as the reference surface is required to have a certain area and height. Referring to FIGS. 1 and 7 , in the example of the linear guide unit 1, it is desirable to use the lower portion 2s of the outer surface 2a of the rail 2 that does not overlap with the table 3 as the reference surface. However, since the rail 2 is a press-formed rail and has a curved surface portion 29a between the bottom surface 27a and the side surface 28a, the portion extending in the height direction (L ₃ ) is small. In particular, when a thick steel plate is used to ensure rigidity, the curved surface portion 29a becomes larger, making it difficult to ensure the reference surface. Here, the rail 2 has a configuration in which a notch is provided in a portion of the side wall portion 28 and a portion of the bottom wall portion 27 extends to the outer surface 2a. This makes it possible to use the end surface 272b as the reference surface S. According to the rail 2 of the present disclosure, even when a press-processed rail made of a thick and highly rigid steel plate is used, the height dimension can be reduced and the necessary reference surface can be secured.

Rail 2 can be produced by cutting a recessed section into a steel plate and then bending it. After bending, end face 272b and face 28b are ground to make them flush, resulting in a highly accurate reference surface. Rail 2 provides a linear motion guide unit that has a reference surface and is compact in height, even when using thick steel plate, without requiring special equipment or processes.

Referring to FIG. 8 , the rail 2 has a bottom wall portion 27 and a side wall portion 28. The bottom wall portion 27 includes a first bottom wall portion 271, a second bottom wall portion 272, and a third bottom wall portion 273. The first bottom wall portion 271, the second bottom wall portion 272, and the third bottom wall portion 273 are continuously connected to form the bottom wall portion 27. The first bottom wall portion 271 is connected to a curved portion 29 and is connected to the side wall portion 28 via the curved portion 29. The second bottom wall portion 272 is wider than the first bottom wall portion 271 and extends across the entire width of the rail 2. As mentioned above, the end surface 272b of the second bottom wall portion 272 forms part of the outer surface 2a of the rail 2. The third bottom wall portion 273 is located between the first bottom wall portion 271 and the second bottom wall portion 272. In other words, the bottom wall portion 27 of the rail 2 is made up of three continuous sections of different widths. Note that the shape of the rail 2 is an example, and the number, dimensions, and spacing of the cutouts can be changed in various ways.

(Variation 1 of the rail)
9 is a perspective view of rail 221, which is a modified example of the rail that constitutes the linear guide unit according to the present disclosure. Rail 221 is similar in many respects to rail 2 described above, but differs from rail 2 in that two recesses 222 are provided at each end of the rail in the longitudinal direction. The recesses 222 are located in the curved portion that connects the bottom wall 27 and side wall 28 of rail 221. The recesses 222 have the effect of reducing deformation of the rail when the steel plate that is the material of the rail is bent.

(Variation 2 of the rail)
10 is a perspective view of rail 225, a modified example of the rail that constitutes the linear guide unit according to the present disclosure. Rail 225 is similar in many respects to rail 2 described above, but differs from rail 2 in that the corners of both longitudinal end faces of the rail are chamfered. There are no particular restrictions on the size of chamfered portion 226, as long as the desired effect can be obtained. Chamfered portion 226 has the effect of reducing deformation of the rail when the steel plate from which the rail is made is bent.

(Modifications of the cage and rolling elements)
FIG. 11 is a perspective view showing a portion of the linear guide unit 11, a modified version of the linear guide unit 1, including the rail 12 and the cage 14. The main difference between the linear guide unit 11 and the linear guide unit 1 is that rollers are used as rolling elements. Descriptions of components similar to those of the linear guide unit 1 will be omitted. As shown in FIG. 11 , the linear guide unit 11 according to the present disclosure may use cylindrical rollers as rolling elements 17. In the linear guide unit 11, multiple rolling elements 17 are arranged in alternating, perpendicular directions. A pair of raceway grooves 121 is formed on both sides of the rail 12 in the longitudinal direction. The raceway groove 121 is defined by an upper raceway surface 121a and a lower raceway surface 121b. The cage 14 is formed with an oval window 141 that rotatably holds the rolling elements 17. Because the linear guide unit 11 uses cross rollers as rolling elements, it can withstand loads from multiple directions, providing a finite linear guide unit with a higher load rating.

The embodiments disclosed herein are illustrative in all respects and should not be considered limiting in any way. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications that are equivalent in meaning to and within the scope of the claims.

1, 11 Linear motion guide unit, 2, 12, 221, 225 Rail, 21, 121 Raceway groove, 22 Notch, 222 Recess, 226 Chamfered portion, 27 Bottom wall portion, 28 Side wall portion, 29 Curved portion, 3 Table, 31 Table body, 311 Top surface portion, 312 Sleeve portion, 32 End plate, 33, 34, 45 Hole, 4, 14 Cage, 41, 141 Window, 42 Retaining plate portion, 43 Connection portion, 51, 52 Rack gear, 6 Pinion gear, 61 Gear portion, 62 Rotating shaft, 7, 17 Rolling element.

Claims (6)

a rail having a pair of first raceway grooves on its side surface;
a table having a pair of second raceway grooves facing the first raceway grooves, respectively;
a plurality of rolling elements that are incorporated in a raceway formed by the first raceway groove and the second raceway groove and that roll in association with movement of the table;
a cage that rotatably holds the rolling elements and moves along the rail as the rolling elements roll;
A linear motion guide unit comprising:
a pair of rack gears fixed to the rail and the table, respectively;
a pinion gear rotatably mounted on the cage and meshing with the pair of rack gears;
Including,
The outer surface of the rail is
a first outer surface portion that is continuous with the bottom surface of the rail via a curved surface;
a second outer surface portion which is an end surface of a steel plate constituting the rail ,
The first outer surface portion and the second outer surface portion are formed flush with each other to form an outer surface of the rail.
Linear guide unit. The rail is
A bottom wall portion;
a pair of side walls rising from both longitudinal ends of the bottom wall,
The bottom wall portion is
a first bottom wall portion connected to the side wall portion via a curved portion between the bottom wall portion and the side wall portion;
a second bottom wall portion that is wider than the first bottom wall portion and extends across the entire width of the rail;
a third bottom wall portion between the first bottom wall portion and the second bottom wall portion.
2. The linear motion guide unit according to claim 1. The rail is constructed from a single steel plate.
3. The linear motion guide unit according to claim 1 or 2. The first outer surface portion and the second outer surface portion, which are formed flush with each other, are used as reference surfaces of the linear motion guide unit.
4. The linear motion guide unit according to claim 1. the cage is made of a single steel plate;
The pinion gear shaft is directly held in a hole formed in the cage.
5. The linear motion guide unit according to claim 1. the hole formed in the cage includes a first hole portion in which a toothed wheel of the pinion gear is rotatable, and a second hole portion that rotatably holds a shaft of the pinion gear,
The width of the second hole portion is 0.1 mm to 0.2 mm larger than the diameter of the pinion gear shaft.
6. The linear motion guide unit according to claim 1.