Ball bush and method of manufacturing the same

Abstract

To provide a ball bush that eliminates the necessity to accurately process the inner diameter dimension of a housing of an apparatus in connection with retaining of the inner diameter dimension in a free state even after the ball bush is inserted into the housing of the apparatus.SOLUTION: A plurality of recesses 12A are formed in an internal peripheral face of an outer cylinder 12 at equal intervals along the axial direction of the outer cylinder 12, and internal peripheral face portions between the plurality of recesses 12A define arc-shaped joining faces 12B. A retainer 14 having protrusions 14A on an external peripheral surface to engage with the recesses 12A is arranged in the outer cylinder 12. A plurality of groove parts 16 for holding a plurality of steel balls 18 are provided in the retainer 14 on an external peripheral side while partially penetrating the internal and external peripheral faces. The positioning of the retainer 14 in the rotation direction with respect to the outer cylinder 12 is determined by engagement of the recesses 12A and the protrusions 14A, such that easy relative rotation is not allowed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a ball bushing and a manufacturing method thereof, in which the inner diameter dimension in a free state is maintained even after the ball bushing is inserted into a housing of an equipment, thereby eliminating the need to machine the inner diameter dimension of the housing of the equipment with high precision. [Background technology]

[0002] A bushing, which is a component used as a bearing and allows the device to rotate around the shaft or move along the shaft, is disposed between a shaft such as a shaft and a device such as a mechanical device supported by the shaft. Among such bushes, a ball bushing is known as a bushing that uses the rolling of steel balls placed inside to reduce friction between the shaft and the bushing.

[0003] In recent years, there has been a demand for ball bushings that are not only capable of reducing friction while still allowing equipment to move, but also that are small and lightweight, leading to the development of compact, thin ball bushings. These thin ball bushings have a smaller outer diameter and a more compact design than typical ball bushings, and are expected to be widely used between equipment and shafts in machinery and other devices.

[0004] On the other hand, the following Patent Document 1 shows that a high press-in force is required to fit the ball bush into the device, which causes the ball bush to deform due to the stress acting on the outer cylinder. Also, the following Patent Document 2 shows a linear guide air cylinder in which both ends of a linear guide inserted into a cylinder tube are supported by fixed members and are arranged so that they can move relative to each other. However, the structure is such that ball bushes A and B for moving along the linear guide are fitted into the inner periphery of both ends of the cylinder tube, respectively. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2001-116043 A [Patent Document 2] JP 2003-74512 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the above-mentioned conventional ball bushings have various problems as described below. In Patent Documents 1 and 2, the ball bushing is press-fitted into the housing or cylinder tube, which is the mounting part inside the device, so the ball bushing does not have a precise inner diameter in a free state, and the precision of the inner diameter of the ball bushing is maintained by the inner diameter of the housing or cylinder tube. Therefore, unless the machining precision of the inner periphery of the device, such as the housing or cylinder tube, is improved and finished precisely, the ball bushing has a disadvantage in that the precision of the inner diameter after installation in the device is poor in relation to the dimensions of the shaft material.

[0007] The drawbacks of the conventional thin ball bushing will be specifically described below. The outer cylinder of the thin ball bushing described above is made of a material with a thickness of 1 mm or less, as it is made using the shell-type pressing method that is generally used for thin ball bushing bearings. Furthermore, by maintaining the durability of this outer cylinder through quenching using a special heat treatment such as nitriding, polishing of the inner and outer diameters after heat treatment is no longer necessary, which has increased the efficiency of ball bushing production.

[0008] However, due to the use of a thin-walled outer cylinder to simplify production, it was difficult to maintain the accuracy of the roundness of the outer diameter dimension by itself. For this reason, the accuracy of the inner diameter of the housing of the device into which the ball bushing is inserted was increased. In other words, since the accuracy of the ball bushing depends on the inner surface of the housing, it was necessary to machine the inner surface of the housing with high accuracy as described above.

[0009] On the other hand, when inserting a thin ball bush into a housing, a press-fit allowance is provided between the housing inner diameter and the ball bush, and it is forcibly pressed in and fixed with a hand press, so the accuracy after assembly is not stable and the ball bush inner diameter tolerance cannot be maintained at a high accuracy. Furthermore, once a ball bush is pressed in, it is not easy to replace it, and even if the ball bush can be removed from the housing, the press-fit allowance disappears and it cannot be used again.

[0010] The present invention has been made in view of the above-mentioned background, and has an object to provide a ball bushing and a manufacturing method thereof, in which the inner diameter dimension in the free state is maintained even after insertion into the housing of the equipment, thereby eliminating the need to machine the inner diameter dimension of the housing of the equipment with high precision. [Means for solving the problem]

[0011] The invention described in claim 1 that solves the above problem is a ball bush that is arranged between a shaft material and a device and guides the device movably relative to the shaft material, An outer cylinder that is disposed in a housing formed in the device and has a cylindrical shape and a plurality of recesses on an inner peripheral surface thereof; a holder that is formed in a cylindrical shape, has a convex ridge on its outer peripheral surface that engages with the concave ridge, is disposed within the outer cylinder, and has grooves that hold a plurality of metal balls and are provided on the outer peripheral side while partially penetrating the inner and outer peripheral surfaces; The ball bushing includes:

[0012] A ball bush as in claim 1 is disposed between a shaft and a device to guide the device movably relative to the shaft. The ball bush has an outer cylinder formed in a cylindrical shape and disposed within a housing formed in the device, and the outer cylinder has a plurality of grooves on its inner peripheral surface. A retainer formed in a cylindrical shape and having protrusions on its outer peripheral surface that engage with the grooves is disposed within the outer cylinder, and a groove for retaining a plurality of metal balls is provided on the outer peripheral side of the retainer while partially penetrating the inner and outer peripheral surfaces.

[0013] Accordingly, since the outer peripheral surface of the holder has a convex rib that engages with the concave rib on the inner peripheral surface of the outer cylinder, the positioning of the holder in the rotational direction relative to the outer cylinder is determined by the engagement of the concave rib and the convex rib, and the holder does not easily rotate relative to the outer cylinder. Furthermore, the outer diameter of the outer cylinder can be made relatively smaller than that of a conventional outer cylinder, and the outer peripheral surface of the outer cylinder does not need to contact the inside of the housing of the device. Therefore, there is no need to press the ball bush into the housing of the device.

[0014] As described above, according to the ball bushing of the present claim, the inner diameter dimension defined by the inscribed circle connecting the shaft side portions of multiple metal balls in a free state is maintained even after the ball bushing is inserted into the housing of the equipment, thereby eliminating the need to machine the inner diameter dimension of the housing of the equipment with high precision.

[0015] According to the ball bushing of the invention of claim 2, the outer cylinder is made of metal and the portion between the multiple recesses is formed in an arc shape. Therefore, by forming the outer surface of the retainer holding the multiple metal balls so that it abuts against the inner surface of the arc-shaped outer cylinder, these are securely fitted together to complete a small ball bushing.

[0016] According to the ball bushing of the invention of claim 3, small metal balls are used, the outer diameter of which is 18% or less of the outer diameter of the shaft material. This makes it possible to more reliably reduce the outer diameter of the outer cylinder, resulting in not only a smaller ball bushing but also a lighter weight.

[0017] The invention described in claim 4 that solves the above problem is a manufacturing method of a ball bushing that is disposed between a shaft material and a device and guides the device to be movable relative to the shaft material, A cylindrical material having an inner peripheral surface formed into a polygon is cut, The polygonal protruding portion on the inner circumferential surface side is evenly and partially removed to form an outer cylinder having a plurality of recesses; This is a manufacturing method for a ball bushing in which a retainer having multiple protrusions on its outer peripheral surface and holding metal balls in grooves is inserted into an outer cylinder while engaging the protrusions with the recesses.

[0018] According to the manufacturing method of the ball bushing of the invention as set forth in claim 4, a ball bushing that is disposed between a shaft material and a device and guides the device to be movable relative to the shaft material can be manufactured and made usable. When manufacturing this ball bushing, first, a cylindrical material with an inner peripheral surface formed into a polygonal shape is cut.

[0019] After this, the polygonal inward protruding portion on the inner peripheral surface is evenly and partially removed to provide multiple concave ridges in the outer tube, and the retainer, which has convex ridges on its outer peripheral surface and holds the metal balls, is inserted into the outer tube while engaging the convex ridges on the outer tube.

[0020] Accordingly, since the outer peripheral surface of the holder has a convex rib that engages with the concave rib on the inner peripheral surface of the outer cylinder, the positioning of the holder in the rotational direction relative to the outer cylinder is determined by the engagement of the concave rib and the convex rib, and the holder does not easily rotate relative to the outer cylinder. Furthermore, the outer diameter of the outer cylinder can be made relatively smaller than that of a conventional outer cylinder, and the outer peripheral surface of the outer cylinder does not need to contact the inside of the housing of the device. Therefore, there is no need to press the ball bush into the housing of the device.

[0021] As described above, according to the manufacturing method of the ball bushing of the present claim, the inner diameter dimension defined by the inscribed circle connecting the shaft side portions of multiple metal balls in a free state is maintained even after the ball bushing is inserted into the housing of the equipment, thereby making it unnecessary to machine the inner diameter dimension of the housing of the equipment with high precision.

[0022] According to the manufacturing method of the ball bushing as claimed in claim 5, the same number of convex ridges are formed on the retainer to match the multiple concave ridges on the inner surface of the outer cylinder, and these convex ridges are fitted into the concave ridges to prevent the retainer from rotating, making it possible to more reliably reduce the outer diameter of the outer cylinder of the ball bushing.

[0023] According to the manufacturing method of a ball bush as claimed in claim 6, small metal balls are used, the outer diameter of each of the metal balls being 18% or less of the outer diameter of the shaft material. This makes it possible to more reliably reduce the outer diameter of the outer cylinder, resulting in the manufacture of a ball bush that is not only compact but also lightweight. Effect of the Invention

[0024] As described above, according to the present invention, the inside diameter dimension in the free state is maintained even after insertion into the housing of the equipment, thereby providing a ball bushing and a manufacturing method thereof that eliminate the need to machine the inside diameter dimension of the housing of the equipment with high precision. [Brief description of the drawings]

[0025] [Figure 1] 1 is a diagram showing a state in which a ball bush according to an embodiment of the present invention is incorporated into a device. [Diagram 2] 1A and 1B are views of a ball bush according to an embodiment of the present invention in a completed state, in which (A) is a front view and (B) is a partially cutaway side view (including the shaft). [Diagram 3] 1 is a perspective view of a ball bush according to an embodiment of the present invention; [Figure 4] 1A and 1B are diagrams showing a retainer that is applied to a ball bush according to an embodiment of the present invention, in which (A) is a front view and (B) is a side view. [Diagram 5] 1 is a diagram showing a state in which a ball bush according to an embodiment of the present invention, the entire length of which is longer than the entire length of a housing, is installed in a device. [Figure 6] 1A and 1B are conceptual diagrams showing a state in which a load is applied to a shaft, where (A) is a conceptual diagram showing a state in the present embodiment, and (B) is a conceptual diagram showing a state in a conventional thin ball bush. [Figure 7] 1A and 1B are diagrams showing a cylindrical material applied to a ball bush according to an embodiment of the present invention, in which (A) is a front view and (B) is a side view. [Figure 8] 1 is a front view showing an outer cylinder that is applied to a ball bushing according to an embodiment of the present invention; [Figure 9] 1A and 1B are diagrams showing the cross-sectional thickness of a cylindrical material, where FIG. 1A shows a cylindrical material according to the present embodiment, and FIG. 1B shows a cylindrical material according to a conventional thin ball bushing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a ball bush and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings. 1, ball bushing 10 according to this embodiment is disposed between shaft 22, which is an axial material, and device 24, such as a mechanical device, and is a member that guides device 24 so that it can move relative to shaft 22. A housing 24A is formed on the inner surface of device 24, which serves as a space for accommodating ball bushing 10, and an outer cylinder 12 that serves as the outer frame of ball bushing 10 is disposed within housing 24A.

[0027] The outer cylinder 12 shown in Fig. 2 is formed into a cylindrical shape from a metal material such as bearing steel, and not only does it have a plurality of grooves 12A (six in this embodiment) on its inner circumferential surface at equal intervals along the axial direction of the outer cylinder 12 as shown in Fig. 3 and Fig. 8, but also the inner circumferential surface portion between these plurality of grooves 12A forms an arc-shaped joint surface 12B. A synthetic resin retainer 14, which is a holder having six equally spaced protrusions 14A on its outer circumferential surface that engage with the grooves 12A as shown in Fig. 4, is formed into a cylindrical shape and disposed within the outer cylinder 12.

[0028] Furthermore, not only is the outer peripheral surface 14B of the retainer 14 formed in a plurality of arcs corresponding to the joint surfaces 12B between the plurality of recesses 12A, but the retainer 14 also has a plurality of grooves 16 (six in total) for holding steel balls 18, which are metal balls, each disposed between the protrusions 14A and the outer peripheral surface 14B. Each of these grooves 16 is formed on the outer peripheral side in an oval shape along the axial direction of the retainer 14, but each groove 16 also partially penetrates the inner and outer peripheral surfaces of the retainer 14.

[0029] As a result, the joint surfaces 12B of the outer tube 12 and the outer peripheral surface 14B of the retainer 14 fit tightly together, and the rotational positioning of the retainer 14 relative to the outer tube 12 is determined by the engagement between the concave ribs 12A and the convex ribs 14A, preventing easy relative rotation.

[0030] On the other hand, as shown in FIG. 2, the multiple steel balls 18 have the same outer diameter. If the outer diameter of the shaft 22 is, for example, 16 mm, the outer diameter of the steel ball 18 is 2.381 mm. Since the outer diameter of the multiple steel balls 18 is 14.88% of the outer diameter of the shaft 22, the outer diameter of the steel ball 18 is 18% or less of the outer diameter of the shaft 22.

[0031] Furthermore, grease or the like for smoothing the rotation of the steel balls 18 is filled into the multiple grooves 16, and sealants 20 for sealing the grease or the like within the grooves 16 are fitted into the annular grooves 12C formed at both ends of the outer tube 12, sandwiching the retainer 14 between them, thereby completing the ball bushing 10 of this embodiment as shown in Figure 3.

[0032] Unlike the above, as with conventional thin ball bushings, even if the overall length L1 of the ball bushing is made longer than the overall length L0 of the housing as shown in FIG. 5, it is possible to use the ball bushing 10 of the above embodiment by providing snap rings 34 on both ends, and it is also possible to use the ball bushing 10 without a housing.

[0033] Next, the operation of the ball bush 10 according to the present embodiment will be described. A ball bushing 10 as in this embodiment is disposed between a shaft 22 and a device 24, and guides the device 24 movably relative to the shaft 22. Furthermore, this ball bushing 10 has a metallic outer tube 12 formed in a cylindrical shape and disposed within a housing 24A formed in the device 24, and not only is a plurality of grooves 12A formed at equal intervals on the inner circumferential surface of this outer tube 12, but the inner circumferential surface portion between the plurality of grooves 12A forms an arc-shaped joint surface 12B.

[0034] A retainer 14 is disposed in the outer cylinder 12. The retainer 14 is cylindrical and has a plurality of equally spaced ridges 14A between a plurality of outer circumferential surfaces 14B that engage with the recesses 12A. A groove 16 for holding a plurality of steel balls 18 is provided on the outer circumferential side of the retainer 14, partially penetrating the inner and outer circumferential surfaces. As described above, the outer diameter of the plurality of steel balls 18 is 2.381 mm, while the outer diameter of the shaft 22 is 16 mm, so that the outer diameter of the plurality of steel balls 18 is 18% or less of the outer diameter of the shaft 22.

[0035] Accordingly, since the protruding stripes 14A that engage with the recessed stripes 12A on the inner peripheral surface of the outer cylinder 12 are provided between the outer peripheral surface 14B formed in an arc shape of the retainer 14, the outer peripheral surface 14B fits tightly in correspondence with the joint surface 12B formed in an arc shape between the plurality of recessed stripes 12A. Therefore, the outer diameter can be made relatively small compared to the conventional outer cylinder, and it is not necessary to contact the outer peripheral surface 14B of the outer cylinder 12 with the inside of the housing 24A of the device 24. As a result, there is no need to press-fit the ball bushing 10 when inserting it into the housing 24A of the device 24.

[0036] As described above, according to the ball bushing 10 of this embodiment, because part of the groove 16 penetrates the inner and outer circumferential surfaces of the retainer 14, part of the steel ball 18 protrudes from the inner circumferential surface of the retainer 14. Accordingly, the inner diameter dimension D shown in Fig. 2 of the inscribed circle connecting the shaft 22 side portions of the multiple steel balls 18 in a free state is maintained even after the ball is inserted into the housing 24A of the device 24, and this eliminates the need to highly accurately machine the inner diameter of the housing 24A, which serves as the space for the device 24.

[0037] Furthermore, since the outer tube 12 is made of metal and the portion between the multiple recesses 12A is formed into an arc-shaped joint surface 12B, the outer peripheral surface 14B of the retainer 14 having the multiple steel balls 18 in the grooves 16 is made to abut against this arc-shaped joint surface 12B of the outer tube 12, and by further attaching the sealing material 20, these are securely fitted together to complete the small ball bushing 10.

[0038] As described above, in this embodiment, small steel balls 18 are used, with the outer diameter of the multiple steel balls 18 being 18% or less of the outer diameter of the shaft 22, which makes it possible to more reliably reduce the outer diameter of the outer cylinder 12, and as a result, not only can the ball bush 10 be made smaller, but it can also be made lighter.

[0039] In a conventional normal ball bushing, if the outer diameter of the shaft 22 is 16 mm, the outer diameter of the steel balls is 3.175 mm, and the outer diameter of the plurality of steel balls is 19.88% of the outer diameter of the shaft 22. In other words, if it exceeds 18%, the effect of sufficiently reducing the weight of the ball bushing 10 cannot be achieved, and it is necessary to use steel balls 18 that are 18% or less of the outer diameter of the shaft 22.

[0040] As a result of the above, by changing the inner diameter shape of the outer cylinder 12 and reducing the diameter of the steel balls 18, the outer diameter of the outer cylinder 12, which is the outer diameter of the ball bushing 10, is approximately 15% smaller in this embodiment than in the conventional case.

[0041] In addition, in the conventional ball bushing, the number of rows for holding the steel balls 18 was generally four as shown in Fig. 6(B), so that the load P applied during actual use was sometimes applied to a single row of steel balls 18. In contrast, in the ball bushing 10 of this embodiment, the number of grooves 16 for holding a plurality of steel balls 18 is increased to six rows, so that the load is distributed as shown in Fig. 6(A) of the ball bushing 10 during actual use, as shown by P1, P2, and P3, and thus the load can be distributed. Furthermore, the outer cylinder 12 of the ball bushing 10 according to this embodiment is not only thicker and stronger than the conventional one, but also has no openings on the outer peripheral surface of the outer cylinder 12, which may have been present on the outer peripheral side of the outer cylinder in the conventional ball bushing, so there is no risk of dust entering the ball bushing 10.

[0042] Next, a manufacturing method of the ball bush 10 according to the present embodiment will be described. When manufacturing the ball bushing 10 of this embodiment, first, a cylindrical material 32, which is a cylindrical deformed pipe material made of bearing steel and has an inner circumferential surface 32A formed in a polygonal shape as shown in Figure 7, is cut to the required length to fit the size of the outer tube 12 to be manufactured.

[0043] After that, the cut cylindrical material 32 is subjected to general oil quenching, and the outer diameter is polished, and the part protruding inward corresponding to the polygon on the inner peripheral surface is polished evenly and partially to remove it. As a result, the outer cylinder 12 having the multiple grooves 12A is individually finished with high precision as shown in Figure 8. Accordingly, the inner peripheral surface part between the multiple grooves 12A cut into an arc shape becomes the arc-shaped joint surface 12B.

[0044] As a result, it is no longer necessary to increase the inner diameter precision of the inner peripheral surface of the housing 24A, and since the ball bushing 10 is not press-fitted into the housing 24A, it is possible to easily replace the ball bushing 10. In other words, since the ball bushing 10 is not press-fitted into the housing 24A, it is also possible to reuse the ball bushing 10.

[0045] On the other hand, it was found that if the cross-sectional area of ​​the outer tube 12 made from cylindrical shaped pipe material is less than 20% of the total cross-sectional area based on the outer diameter of the outer tube 12, it is affected by the housing inner diameter tolerance. For this reason, in ball bushing 10 according to this embodiment, outer cylinder 12 has a cross-sectional area in the range of 20% or more, which is the limit value that is not affected by the inner diameter tolerance of the housing, but the outer diameter dimension of this outer cylinder 12 is approximately the same as that of a conventional thin ball bushing. And, by identifying this limit value, the disadvantages of the conventional thin ball bushing have been eliminated, which is a major feature of ball bushing 10 according to this embodiment.

[0046] Specifically, in relation to the housing inner diameter dimension, tests were conducted using two types of thin ball bushings under strict conditions of tight clearance K6 (tolerance = 24.002 to 23.989 mm for an inner diameter of 24 mm).First, using cylindrical material 32 of this embodiment and a conventional simple ring-shaped cylindrical material 114, both of which have almost the same outer diameter, dimension A of the thinnest part of cylindrical material 32 shown in Fig. 9(A) and dimension A of cylindrical material 114 shown in Fig. 9(B) were measured, and the data are shown in Table 1 below.

[0047] [Table 1]

[0048] In this case, the total cross-sectional area of ​​each outer diameter is 452.16 mm 2 (Outer diameter 24.0 mm) compared to 455.93 mm for conventional cylindrical material 114 2 (Outer diameter 24.1 mm), and the wall thickness of each outer diameter is 2.8% for the cylindrical member 32 and 3.5% for the cylindrical member 114. However, since the inner peripheral surface of the cylindrical member 32 is hexagonal, the cross-sectional area is 95.365 mm 2 was larger than the cross-sectional area of ​​the cylindrical material 114.

[0049] Two types of ball bushings, that is, the ball bushing 10 according to the present embodiment made of the cylindrical member 32 as described above and the conventional thin ball bushing made of the cylindrical member 114, were fitted into a housing. Then, the ball bushing 10 according to the present embodiment was inserted by light tapping into a housing (not shown) that had been machined to an actual inside diameter of 23.989 mm. When the inside diameter dimension was then checked with a go / no go gauge, the go gauge went in and the stop gauge did not go in, meaning that there was no effect on the inside diameter of the ball bushing.

[0050] On the other hand, the conventional thin ball bushing made of cylindrical material 114 had a smaller inner diameter after being inserted into the housing, and the go-through gauge did not fit, so it was rejected as a product. In other words, although the original outer diameter of cylindrical material 114 was 24.1 mm, as the outer diameter became smaller, the inner diameter also shrunk, making it unsuitable for practical use.

[0051] As a result of the above, the ratio of the cross-sectional area to the outside diameter of the cylindrical material 32 was 21.08%, while that of the cylindrical material 114 was 15.98% because the outside diameter of the cylindrical material 114 had shrunk to about 24.0 mm, and only the cylindrical material 32 applied to this embodiment was within the range of 20% or more, which is considered to be the limit value. Note that since the upper limit of the limit value is considered to be about 25%, the limit value may be set to 20% to 25%.

[0052] Next, the retainer 14 is manufactured. This retainer 14 is made of synthetic resin and is manufactured using a molding die or the like. At this time, a plurality of ridges 14A are formed on the outer peripheral surface 14B in accordance with the positions of the plurality of grooves 12A of the outer cylinder 12, and the outer peripheral surface side of this retainer 14 is also made to have an arc-shaped outer peripheral surface 14B in correspondence with the joint surface 12B between the plurality of arc-shaped grooves 12A of the outer cylinder 12. Furthermore, grooves 16 are provided between each of the arc-shaped outer peripheral surfaces 14B and the ridges 14A, and a plurality of steel balls 18 are placed in these grooves 16, and grease or the like for smoothing the rotation of the steel balls 18 is filled in and held in place.

[0053] Thereafter, the retainer 14, which holds the steel balls 18, is inserted into the outer cylinder 12 while engaging the ridges 14A on the outer peripheral surface 14B with the grooves 12A of the outer cylinder 12. As a result, the outer peripheral surface 14B of the retainer 14, which is formed in an arc shape corresponding to the mating surface 12B of the outer cylinder 12, fits tightly into this mating surface 12B. As a result, in the ball bushing 10 of this embodiment, the ridges 14A are fitted into the grooves 12A to prevent the retainer 14 from rotating, so that it is possible to more reliably reduce the outer diameter of the outer cylinder 12.

[0054] Furthermore, sealants 20 for sealing grease or the like are fitted into both ends of the outer cylinder 12 with the retainer 14 sandwiched between them in the multiple grooves 16, completing the ball bushing 10 according to this embodiment as shown in Figures 2 and 3. Finally, as shown in Figure 1, by disposing the ball bushing 10 between the shaft 22 and the device 24, the device 24 can be guided by the ball bushing 10 so as to be movable relative to the shaft 22. At this time, the ball bushing 10 may be positioned within the device 24 by a snap ring or the like.

[0055] Accordingly, since the outer peripheral surface 14B of the retainer 14 has the ridges 14A that engage with the grooves 12A on the inner peripheral surface of the outer cylinder 12, the outer diameter of the outer cylinder 12 becomes relatively small, and it is not necessary for the outer peripheral surface 14B of the outer cylinder 12 to contact the inside of the housing 24A of the device 24. Therefore, when inserting the ball bushing 10 into the housing 24A of the device 24, there is no need to press it in.

[0056] As described above, according to the manufacturing method of ball bushing 10 of the present embodiment, the inner diameter dimension D shown in FIG. 2 of the inscribed circle connecting the shaft 22 side portions of multiple steel balls 18 in a free state is maintained even after the ball bushing 10 is inserted into housing 24A of device 24, so that a ball bushing 10 can be obtained that does not require highly accurate machining of the inner diameter dimension of housing 24A of device 24.

[0057] In the above embodiment, the outer tube 12 and the steel balls 18 are made of metal, but it is possible to use, for example, high carbon chromium bearing steel. Also, the retainer 14 is made of synthetic resin, but it is possible to use, for example, polyacetal resin, and it is possible to use a rubber-based material such as nitrile rubber as the material for the sealant 20. And, it is possible to use, for example, a hexagonal shape for the inner peripheral surface side of the cylindrical material 32 for manufacturing the outer tube 12, but it is possible to use any cylindrical material having a shape from a triangle to a dodecagon.

[0058] On the other hand, the diameter of the steel balls 18 is about 20 to 30 percent smaller than in the conventional case, and therefore the number of steel balls 18 is about 80 percent more than in the conventional case. Accordingly, the number of grooves 16 is also greater than in the conventional case. Furthermore, although the present embodiment has been described using a shaft material with an outer diameter of 16 mm, the present invention is also applicable to shaft materials with other outer diameters, such as 6 mm, 8 mm, 10 mm, 13 mm, and 20 mm.

[0059] Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible based on the spirit of the present invention, and these are not excluded from the scope of the present invention. [Industrial Applicability]

[0060] The ball bushing of the present invention is a linear motion mechanism for rolling guides, and is used in combination with a linear shaft to achieve infinite linear motion by utilizing the rolling of steel balls. Since it provides low-friction, highly accurate linear motion, it is ideal for use in a variety of mechanical devices, including automobiles and other vehicles, railway cars, and robots. [Explanation of symbols]

[0061] 10 Ball bushing 12 Outer cylinder 12A groove 12B Joint surface 14 Retainer 14A Convex strip 14B Outer surface 16 Groove 18 Steel ball (metal ball) 20 Encapsulating material 32 Cylindrical material

Claims

1. A ball bushing is disposed between a shaft member and a device, and guides the device movably relative to the shaft member, An outer cylinder that is disposed in a housing formed in the device and has a cylindrical shape and a plurality of recesses on an inner peripheral surface thereof; a holder that is formed in a cylindrical shape, has a convex ridge on its outer peripheral surface that engages with the concave ridge, is disposed within the outer cylinder, and has grooves that hold a plurality of metal balls and are provided on the outer peripheral side while partially penetrating the inner and outer peripheral surfaces; Including ball bushing.

2. 2. The ball bushing according to claim 1, wherein the outer cylinder is made of metal, and the portions between the plurality of grooves are formed in an arc shape.

3. 3. The ball bushing according to claim 1, wherein the outer diameter of the plurality of metal balls is set to 18% or less of the outer diameter of the shaft material.

4. A method for manufacturing a ball bushing that is disposed between a shaft material and a device and guides the device to be movable relative to the shaft material, comprising the steps of: A cylindrical material having an inner peripheral surface formed into a polygon is cut, The polygonal protruding portion on the inner circumferential surface side is evenly and partially removed to form an outer cylinder having a plurality of recesses; A manufacturing method for a ball bushing in which a retainer having multiple protrusions on its outer surface and holding metal balls in grooves is inserted into an outer cylinder while engaging the protrusions with the recesses.

5. 5. A method of manufacturing a ball bushing according to claim 4, wherein the retainer is formed with the same number of protrusions to match the plurality of recesses on the inner peripheral surface of the outer cylinder, and these protrusions are fitted into the recesses to prevent the retainer from rotating relative to the outer cylinder.

6. 6. The method for manufacturing a ball bushing according to claim 4, wherein the outer diameter of the plurality of metal balls is set to 18% or less of the outer diameter of the shaft material.

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