JP7567627B2 - Rolling guide device - Google Patents

Description

The present invention relates to a rolling guide device used in measuring machines, machine tools, etc., that guides a reciprocating object in the direction of its movement.

Conventionally, a linear guide as a rolling guide device generally has a guide rail with rail-side rolling grooves on the left and right side surfaces, a slider with slider-side rolling grooves at a position facing the rail-side rolling groove of the guide rail, and a number of rolling elements that are filled in a load 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 and can roll on these rolling paths. End caps are attached to both axial ends of the slider, and a direction change path is formed inside the end cap to change the direction of the rolling elements. Then, the slider moves relative to the guide rail along the axial direction as the rolling elements roll on the rolling path consisting of the load rolling path, rolling element return path, and direction change path. After changing direction inside the end cap, the rolling elements that roll on the rolling path return to their original position through the rolling element return path formed inside the slider.

In such a linear guide, the surfaces of adjacent rolling elements move in opposite directions within the loaded rolling path, and frictional forces generated at the contact points between the rolling elements can hinder smooth operation of the slider or cause the rolling elements to compete with each other.
In addition, since the rolling element return path and the direction change path are formed larger than the diameter of the rolling elements, the rolling elements in the rolling element return path and the direction change path move by being pushed by the rolling elements in the loaded rolling path, and as with the loaded rolling path, competition occurs between the rolling elements, reducing operability.
In order to improve the operability of the rolling guide device, various types of spacers have been disclosed that are disposed between adjacent rolling elements.

For example, Patent Document 1 describes a linear motion device in which a cage is interposed between adjacent circulating balls. The cage has two concave ball receiving sections back to back, and a ball hole is provided in the center of the ball receiving section. A spacer ball, which has a much smaller diameter than the circulating ball, is fitted into the ball hole with both sides exposed and free to rotate. In the linear motion device described in Patent Document 1, when adjacent circulating balls come into contact with the spacer balls at the same time, the sliding resistance between the circulating balls and the ball receiving sections decreases, resulting in suppression of torque fluctuations in the linear motion device.

Patent Document 2 also discloses a rolling guide device in which the rolling elements are composed of multiple first rolling elements and multiple second rolling elements (elastic balls) made of an elastic material, improving the operability of the slider. The elastic balls are resin balls with protrusions, grooves, or holes on the surface to reduce the elastic modulus of the balls. By using the elastic balls, the pushing of the loaded balls in the circulation path is eliminated by the elastic deformation of the elastic balls, preventing malfunctions of the linear guide device, etc.

JP 2003-247619 A International Publication No. 2016/190147

In the linear motion device described in Patent Document 1, the spacer balls are normally held so as not to come into contact with adjacent circulating balls at the same time, and the adjacent circulating balls must be set in a shape such that they come into contact with the spacer balls only when the ball receiving portion is deformed by a predetermined amount due to the pressing force of the circulating balls. This makes the design of the spacer complicated, and there is a risk that the cage may collapse due to wear, resulting in malfunction.
In addition, when assembling the linear motion device, the circulating balls and spacers need to be inserted alternately into the slider, and the spacers need to be positioned so that they are accurately held by the circulating balls on both sides, which reduces work efficiency during assembly.

Furthermore, in the rolling guide device described in Patent Document 2, since protrusions, grooves, or holes are provided only on the surface of the resin ball, the elastic modulus is low only on the surface, and it is difficult to reduce the elastic modulus of the entire ball. Also, with long-term use, the ball surface deteriorates with age and oil and hardens, increasing the elastic modulus. Therefore, it is not possible to maintain a small elastic modulus for a long period of time.
The above-mentioned Patent Document 2 also proposes an elastic ball consisting of a ball body and a cover that tightly covers the surface of the ball body, and an elastic ball consisting of only this cover. However, because the cover covers the ball body without any gaps, the manufacturing method for an elastic ball consisting of only the cover is complicated and the manufacturing costs are also high.

The present invention was made in consideration of the above-mentioned problems, and its purpose is to provide a rolling guide device that is easy to assemble, has excellent operability, and can reduce manufacturing costs.

The above object of the present invention can be achieved by the following configuration.
(1) 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 rolling element rolling path including 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 and the other end of the loaded rolling path, and a plurality of rolling elements are filled in the rolling element rolling path so as to be capable of rolling;
A rolling guide device in which one of the first member and the second member moves relative to the other by the rolling body rolling,
the plurality of rolling elements are constituted by a plurality of load balls and a plurality of spacer balls having a modulus of elasticity smaller than that of the load balls,
The spacer ball has a gap provided therein and an opening provided on the outer circumferential surface thereof, the opening reaching the gap.

According to the present invention, the rolling element rolling path is filled with load balls and spacer balls whose shape is specified so that the elastic modulus is smaller than that of the load balls. This makes assembly easy, and by suppressing the rolling elements from competing with each other in the rolling path, it is possible to provide a rolling guide device that has excellent operability and can reduce manufacturing costs.

1 is a perspective view showing a rolling guide device according to an embodiment of the present invention, with a rolling body rolling path partially cut away. FIG. 2 is a cross-sectional view that illustrates the rolling guide device illustrated in FIG. 1 . 1A and 1B are diagrams showing a spacer ball of a rolling guide device according to a first embodiment of the present invention, in which (a) is a perspective view and (b) is a cross-sectional view taken along line III-III in (a). 4A and 4B are diagrams showing a schematic cross section taken along line IV-IV in FIG. 2, in which FIG. 4A shows the state before movement and FIG. FIG. 6 is a cross-sectional view showing a spacer ball of a rolling guide device according to a second embodiment of the present invention. FIG. 11 is a cross-sectional view showing a spacer ball of a rolling guide device according to a third embodiment of the present invention. FIG. 11 is a perspective view showing a spacer ball of a rolling guide device according to a fourth embodiment of the present invention.

The rolling guide device according to the present invention will be described in detail below with reference to the drawings. Note that the present invention is not limited to the embodiment described below, and can be modified as appropriate without departing from the gist of the present invention.

First, a rolling guide device according to a first embodiment of the present invention will be described with reference to Figures 1 to 3. In this embodiment, a linear guide device is used as an example of the rolling guide device.

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

Two upper and lower track grooves (first track grooves) 3 extending in the axial direction are formed on the left and right side surfaces of the guide rail 1. The slider 2 comprises a slider body 9 having sleeves 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.

Two raceway grooves (second raceway grooves) 7 facing 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 raceway grooves 3 and the raceway grooves 7 arranged opposite each other define two load rolling paths 22 on each of the left and right sides.
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 thereof, and the loaded rolling path 22 and the unloaded rolling path 21 form a rolling body rolling path 23 .

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 to have a generally U-shaped cross section similar to the slider body 9.
The end cap 5 , together with a return guide (not shown), constitutes a direction change path of the unloaded rolling path 21 .

A total of four rolling element rolling paths 23 are provided inside the slider 2, and a plurality of steel balls (load balls) 6 and a plurality of spacer balls 16 are filled in the rolling element rolling paths 23 so that they can roll freely. As shown in FIG. 3, a void 17 is provided at the center of the spacer ball 16, and openings 18a and 18b are formed on the outer circumferential surface 16a thereof, which reach the void 17 from two opposing directions. That is, in this embodiment, a cylindrical through hole 19 is formed by the void 17 and the openings 18a and 18b, and this through hole 19 has a smaller elastic modulus than the steel ball 6. The plurality of steel balls 6 and spacer balls 16 circulate endlessly while rolling in the rolling element rolling paths 23 as the guide rail 1 and the slider 2 move relative to each other.

In this embodiment, the spacer balls 16 have a specific shape to prevent deterioration of operability due to the steel balls 6 competing against each other in the unloaded rolling path. First, the deterioration of operability caused by the steel balls 6 competing against each other will be described in detail below with reference to FIG. 4. FIG. 4 shows the rolling body rolling path 23 of the linear guide device 10 shown in FIGS. 1 and 2.

The rolling element rolling path 23 is filled with only steel balls 6 as rolling elements. The unloaded rolling path 21 is a path for realizing infinite circulation of the steel balls 6, and is formed larger than the diameter of the steel balls 6, and is composed of a combination of straight and curved sections. The loaded rolling path 22 is sandwiched between the raceway groove 3 of the guide rail and the raceway groove 7 of the slider, and is a path where the steel balls 6 receive a preload load or an external load. In such a rolling element rolling path 23, the amount of movement changes between the steel balls 6 (entrance side rolling elements) that enter the unloaded rolling path 21 from the loaded rolling path 22 and the steel balls 6 (exit side rolling elements) that exit the unloaded rolling path 21 from the unloaded rolling path 21. Hereinafter, this change in amount of movement is referred to as the change in amount of entry and exit.

The steel balls 6 located in the loaded rolling path 22 rotate and revolve due to the movement of the slider. The steel balls 6 located in the unloaded rolling path 21 are pushed and moved by the steel balls 6 in the loaded rolling path 22. Figures 4(a) and 4(b) show the same rolling body rolling path 23, but show a state in which the position of the reference steel ball 6 is slightly shifted before and after the slider moves in the direction indicated by the arrow in the figure. As described above, the steel balls 6 in the unloaded rolling path 21 are pushed and moved, so they are arranged without any gaps. At this time, the number of steel balls 6 present in the unloaded rolling path 21 varies slightly depending on the position of the reference steel ball 6a. For example, in Figure 4(a), there are 10.42 steel balls 6 in the unloaded rolling path 21, and in Figure 4(b), there are 10.4 steel balls 6. In this way, when the slider moves in the direction indicated by the arrow, the number of steel balls 6 that can exist in the unloaded rolling path 21 decreases, causing a change in the amount of movement, and the steel balls 6 in the loaded rolling path 22 are unable to move at a constant speed. As a result, the steel balls 6 temporarily become difficult to rotate, and the apparent frictional force between the slider 2 and the guide rail 1 momentarily increases.

Even in the loaded rolling path 22, slight differences in speed occur between the steel balls 6 due to slight errors in the groove shape. At this time, the faster steel balls push the slower steel balls, and the steel balls 6 may compete with each other. As a result, just like in the unloaded rolling path 21, the steel balls 6 temporarily become difficult to rotate, and the apparent frictional force between the slider 2 and the guide rail 1 momentarily increases.

In this way, if only steel balls 6, which are almost rigid bodies, are used, even a slight difference in the number of balls that can exist in the unloaded rolling path 21 will hinder the movement of the steel balls 6 present in the loaded rolling path 22. Therefore, in this embodiment, spacer balls 16 with a smaller elasticity than the steel balls 6 are placed in the rolling body rolling path 23 to reduce competition between the steel balls 6, absorb changes in frictional force, and not hinder the revolution of the steel balls 6.

Even if the spacer balls have a smaller elastic modulus than the steel balls 6, such as synthetic rubber, and the material itself has a small elastic modulus, the competition between the steel balls 6 can be alleviated and the operability of the linear guide device can be improved. However, if the material of the spacer balls is selected to reduce the elastic modulus, the durability of the linear guide device will decrease. This is because materials with a small elastic modulus generally have low abrasion resistance. The spacer balls circulate together with the steel balls 6 in the rolling body rolling path 23 of the linear guide device 10, colliding with the steel balls 6 and other parts in the rolling body rolling path 23, and circulating while colliding with them and with other parts in the rolling body rolling path 23 and with contact sliding. Therefore, spacer balls made of a material with a small elastic modulus may be scraped or worn when they collide with the circulating parts that make up the rolling body rolling path 23. On the other hand, if spacer balls are made of a material that is highly resistant to scraping and abrasion, the elastic modulus will generally be large.

In this embodiment, a larger portion of the volume of the spacer balls 16 is hollowed out to provide the voids 17, thereby reducing the elastic modulus of the entire spacer ball and increasing the deformation caused by an external force (steel balls pushing against each other). In other words, by arranging the spacer balls 16 having the above-mentioned shape in the rolling element rolling path 23, slight changes in the amount of movement in and out can be absorbed by the elasticity. As a result, the movement of the steel balls 6 in the load rolling path 22 can be made smooth, and a rolling guide device with excellent operability can be obtained.
Furthermore, rather than imparting elasticity by forming irregularities on the surface of the spacer ball or by selecting the material of the spacer ball, the elastic modulus of the entire spacer ball is reduced by providing voids inside, so that the elastic modulus can be maintained low for a long period of time.
Furthermore, by appropriately selecting the shape of the spacer balls 16 and reducing the elastic modulus, it is possible to further improve the effect of the spacer balls 16 as a buffer against the collision of the steel balls 6. Therefore, it is possible to improve the durability of the linear guide device.

Here, when a through hole is formed in the spacer ball 16, a part of the outer circumferential surface of the sphere is flattened, which may hinder rotation, but in the first embodiment shown in Fig. 3(b), the spacer ball 16 is formed so that the sphericity of the spacer ball 16 does not decrease significantly. Specifically, when a cylindrical through hole having a diameter of 2 mm and passing through the center is formed in a spacer ball 16 having a diameter of 6.35 mm, the width of the part where the ball diameter is smallest is 5.84 mm, which is only about 8% smaller than the original ball diameter. Therefore, it is possible to realize a reduction in the elastic modulus and maintain the function of the spacer ball 16 rotating.
Furthermore, the through hole 19 does not necessarily have to pass through the center, and by appropriately selecting the diameter of the cylindrical through hole and the number of through holes to be formed, a spacer ball 16 can be obtained that can simultaneously reduce the elastic modulus and maintain rotational function.

The shapes of the spacer balls used in the second to fourth embodiments of the present invention will be specifically described below with reference to FIGS.
5, a gap 27 is provided in the center of a spacer ball 26, and an opening 28 is formed in an outer circumferential surface 26a of the spacer ball 26, which reaches the gap 27. That is, in the second embodiment, a cylindrical blind hole 29 is formed by the gap 27 and the opening 28, and this blind hole 29 can have a smaller elastic modulus than that of the steel ball 6.

In the third embodiment shown in Fig. 6, the spacer ball 36 is provided with a spherical gap 37, and the outer peripheral surface 36a of the spacer ball 36 is provided with an opening 38 that reaches the gap 37. The thickness t, which is obtained by dividing the difference between the outer diameter D and the inner diameter d of the spacer ball 36 in half, is formed to be uniform in the region excluding the opening 38. The spacer ball 36 having such a configuration can be easily manufactured at low cost by blow molding. Since the thickness t is uniform in the region excluding the opening 38, excellent elasticity can be obtained in any direction, and even if the diameter of the opening 38 is reduced to improve the rotation function, the desired elastic modulus can be obtained by adjusting the thickness t.
It should be noted that the thickness t does not need to be precisely uniform in the region excluding the opening 38, and any errors in thickness that may occur during manufacturing are included in the present invention.

Furthermore, in the fourth embodiment shown in FIG. 7, the spacer ball 46 has three through holes 49a, 49b, and 49c that pass through the center, and a gap 47 is formed at the center where these through holes 49a, 49b, and 49c intersect. That is, through hole 49a is formed by openings 48a and 48b and gap 47, through hole 49b is formed by openings 48c and 48d and gap 47, and through hole 49c is formed by openings 48e and 48f and gap 47. Although the mold structure of such a spacer ball 46 is complicated, it can be easily manufactured at low cost by injection molding.

As described above, the spacer balls 16, 26, 36, and 46 used in the rolling guide devices according to the first to fourth embodiments all have a smaller modulus of elasticity than the steel balls. Therefore, by being present together with the steel balls in the unloaded rolling path 21 or the loaded rolling path 22, they function as a buffer against the steel balls competing with each other, and good operability can be obtained.

In addition, the spacer balls 16, 26, 36, and 46 of the rolling guide device according to each of the above embodiments have internal gaps 17, 27, 37, and 47, so that lubricant can be filled into these gaps 17, 27, 37, and 47. Therefore, by using spacer balls 16, 26, 36, and 46 filled with lubricant, even better operability can be obtained.

In each of the above embodiments, the materials of the spacer balls 16, 26, 36, and 46 are not particularly limited, but it is preferable to select a material that is highly resistant to slippage and collisions (abrasion resistance), for example, one selected from resins (such as polyacetal) and thermoplastic elastomers. Spacer balls 16, 26, 36, and 46 made of such materials can be manufactured by injection molding, thereby reducing manufacturing costs.

If the spacer balls 16, 26, 36, 46 of the rolling guide device according to each of the above embodiments are made larger than the loaded balls, they will create resistance when moving from the unloaded rolling path 21 to the loaded rolling path 22, resulting in significantly poorer operability. Furthermore, if the diameter of the spacer balls 16, 26, 36, 46 is 90% or more of the diameter of the loaded balls, the frictional force generated at the contact points between the rolling elements in the loaded rolling path can be reduced. Therefore, it is preferable that the diameter of the spacer balls 16, 26, 36, 46 is 90% or more and 100% or less of the diameter of the loaded balls.

In addition, in the rolling guide devices according to the above embodiments, the number of spacer balls 16, 26, 36, 46 is set to multiple (two or more). This ensures that at least one spacer ball is always present in the unloaded rolling path 21, so that the effect of absorbing the competition between the steel balls 6 can be fully obtained. On the other hand, if the number of spacer balls 16, 26, 36, 46 becomes too large, the load capacity decreases, so it is preferable that the number of spacer balls 16, 26, 36, 46 is less than the number of loaded balls.

Furthermore, it is preferable that the plurality of spacer balls 16, 26, 36, 46 are arranged at approximately equal intervals between the steel balls 6. This increases the probability that at least one spacer ball 16, 26, 36, 46 is arranged in the unloaded rolling path and at least one spacer ball 16, 26, 36, 46 is arranged in the loaded rolling path. As a result, friction between the steel balls can be suppressed and competition can be reduced even in the loaded rolling path.
Note that "approximately equal intervals" refers to the number of steel balls between adjacent spacer balls 16, 26, 36, 46 being n or n+1 (n is any integer).

In the above embodiment, steel balls 6 are used as the load balls, but the load balls are not limited to being made of metal, and ceramics, etc. may also be used. In the above embodiment, a linear guide device is used as an example of a rolling guide device, but the present invention can also be applied to a ball screw.

As described above, the present specification discloses the following:
(1) 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 rolling element rolling path including 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 and the other end of the loaded rolling path, and a plurality of rolling elements are filled in the rolling element rolling path so as to be capable of rolling;
A rolling guide device in which one of a first member and a second member moves relatively to the other member as the rolling body rolls,
the plurality of rolling elements are constituted by a plurality of load balls and a plurality of spacer balls having a modulus of elasticity smaller than that of the load balls,
The spacer ball has a gap provided therein and an opening provided on the outer circumferential surface thereof, the opening reaching the gap.
According to this structure, the assembly work is easy, excellent operability is obtained, and the manufacturing cost of the rolling guide device can be reduced.

(2) The rolling guide device according to (1), wherein a lubricant is filled in the gaps of the spacer balls.
According to this configuration, the operability of the rolling guide device can be further improved.

(3) The rolling guide device according to (1) or (2), wherein the gap is provided at the center of the spacer ball.
According to this configuration, it is possible to maintain the rotation performance of the spacer balls while reducing the elastic modulus.

(4) The rolling guide device according to any one of (1) to (3), wherein the gap and the opening form a cylindrical through hole.
According to this configuration, the rolling guide device can be manufactured easily and at low cost.

(5) The rolling guide device according to (3), in which the gap and the opening form a cylindrical blind hole.
According to this configuration, the rolling guide device can be manufactured easily and at low cost.

(6) The rolling guide device according to (3), wherein the gap is spherical, and the spacer ball has a uniform thickness in a region other than the opening.
According to this configuration, it can be easily manufactured at low cost, and excellent elasticity can be obtained in any direction. By adjusting the thickness, a desired elastic modulus can be obtained.

(7) The rolling guide device according to any one of (1) to (6), wherein the spacer balls are made of one material selected from the group consisting of resin and thermoplastic elastomer.
According to this configuration, the spacer balls can be configured to have both elasticity and durability.

(8) The rolling guide device according to any one of (1) to (7), wherein the diameter of the spacer balls is 90% or more and 100% or less of the diameter of the load balls.
According to this configuration, friction between the loaded balls in the loaded rolling path can be suppressed, and the operability of the rolling guide device can be further improved.

1 Guide rail (first member)
2 Slider (second member)
3 raceway groove (first raceway groove)
4 Sleeve portion 5 End cap 6, 6a Steel ball (load ball)
7 raceway groove (second raceway groove)
9 Slider body 10 Linear guide device (rolling guide device)
16, 26, 36, 46 Spacer balls 17, 27, 37, 47 Gap portion 18a, 18b, 28, 38, 48a, 48b Opening portion 19, 49a, 49b, 49c Through hole 29 Blind hole 21 Unloaded rolling path 22 Loaded rolling path 23 Rolling body rolling path

Claims (6)

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 rolling element rolling path including 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 and the other end of the loaded rolling path, and a plurality of rolling elements are filled in the rolling element rolling path so as to be capable of rolling;
A rolling guide device in which one of the first member and the second member moves relative to the other by the rolling body rolling,
the plurality of rolling elements are constituted by a plurality of load balls and a plurality of spacer balls having a modulus of elasticity smaller than that of the load balls,
the spacer ball has a gap provided therein and an opening provided on an outer circumferential surface thereof and reaching the gap;
The gap and the opening form a cylindrical through hole . The rolling guide device according to claim 1 , wherein the gap is provided at the center of the spacer ball. 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 rolling element rolling path including 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 and the other end of the loaded rolling path, and a plurality of rolling elements are filled in the rolling element rolling path so as to be capable of rolling;
A rolling guide device in which one of the first member and the second member moves relative to the other by the rolling body rolling,
the plurality of rolling elements are constituted by a plurality of load balls and a plurality of spacer balls having a modulus of elasticity smaller than that of the load balls,
the spacer ball has a gap provided therein and an opening provided on an outer circumferential surface thereof and reaching the gap;
the gap is provided at the center of the spacer ball,
The gap and the opening form a cylindrical blind hole. 4. The rolling guide device according to claim 1, wherein a lubricant is filled in the gaps of said spacer balls. 5. The rolling guide device according to claim 1, wherein the spacer balls are made of one material selected from the group consisting of resin and thermoplastic elastomer. 6. The rolling guide device according to claim 1 , wherein a diameter of said spacer balls is 90% or more and 100% or less of a diameter of said load balls.

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