Cylinder

Abstract

A cylinder (40) includes a cylinder body (24), a ball bush (10), and a rod (22). The ball sleeve includes an outer cylinder (12), a plurality of metal balls (18), and a holder (14), the inner peripheral surface of the outer cylinder is provided with a recessed portion (12A), the holder is provided with a protruding portion (14A) which restricts the rotation of the holder with respect to the outer cylinder by being inserted into the recessed portion, and a groove portion (16) which penetrates from the outer peripheral surface to the inner peripheral surface of the holder and in which the plurality of metal balls are disposed.

Description

Technical Field

[0001] The utility model relates to a cylinder. Background Art

[0002] Prior Art Documents

[0003] In Japanese Patent Laid-Open No. 2001-116043, a cylinder formed by press-fitting a ball bushing into a bushing hole of a cylinder body is described. In addition, in Japanese Patent Laid-Open No. 2003-74512, a linear guide cylinder in which ball bushings are embedded in the inner circumferences at both ends of a cylinder barrel is described. Summary of the Utility Model

[0004] Problems to be Solved by the Utility Model

[0005] A better cylinder is expected.

[0006] The purpose of the present utility model is to solve the above problems.

[0007] The present disclosure is a cylinder, comprising: a cylinder body in which a bushing hole is formed; an annular ball bushing disposed in the bushing hole; and a rod inserted into a hole inside the ball bushing. The ball bushing includes: an outer cylinder disposed in the bushing hole; a plurality of metal balls that are in contact with the outer circumferential surface of the rod in a state of being disposed inside the outer cylinder; and a cylindrical holding member for holding the plurality of metal balls. A recess is provided on the inner circumferential surface of the outer cylinder, and on the holding member are provided: a convex portion that restricts rotation of the holding member relative to the outer cylinder by being inserted into the recess; and a groove portion that penetrates from the outer circumferential surface to the inner circumferential surface of the holding member and in which the plurality of metal balls are disposed.

[0008] According to the present utility model, a better cylinder can be obtained.

[0009] From the following description of embodiments with reference to the drawings, the above objects, features and advantages can be easily understood. Brief Description of the Drawings

[0010] Figure 1 is a partially omitted schematic view of a cylinder assembled with a ball bushing according to an embodiment of the present utility model.

[0011] Figure 2A is a front view of the ball bushing. Figure 2B is a partially cut-away side view of the ball bushing.

[0012] Figure 3 is a perspective view of the ball bushing.

[0013] Figure 4A is a front view of a retainer applicable to the ball bushing.Figure 4B It is a side view of the retainer.

[0014] Figure 5 It is a view of the state in which a ball bushing longer than the full length of the bushing hole is assembled into the cylinder body.

[0015] Figure 6A It shows Figure 1 A conceptual diagram of the state in which a load is applied to the rod in the ball bushing shown. Figure 6B It is a conceptual diagram of the state in which a load is applied to the rod in an existing thin ball bushing.

[0016] Figure 7A It is a front view of a cylindrical component applicable to a ball bushing. Figure 7B It is a side view of the cylindrical component.

[0017] Figure 8 It is a front view of an outer cylinder applicable to a ball bushing.

[0018] Figure 9A It is a view showing the cross-sectional thickness of the cylindrical component. Figure 9B It is a view showing a cylindrical part applicable to a conventional thin ball bushing.

[0019] Figure 10 It is a longitudinal sectional view of the cylinder. Detailed Description

[0020] In a cylinder obtained by press-fitting a ball bushing into a bushing hole of a cylinder body, the inner diameter accuracy of the ball bushing is maintained by the inner diameter dimension of the bushing hole. Therefore, in the case where the machining accuracy of the inner peripheral surface of the bushing hole of the cylinder body cannot be improved and precision finishing is performed, due to the relationship with the dimensions of the rod, in the state after assembling the ball bushing into the bushing hole, there is a drawback that the accuracy of the inner diameter dimension of the ball bushing is poor.

[0021] Hereinafter, the drawbacks of the conventional thin ball bushing will be specifically described. Since the outer cylinder of the thin ball bushing is formed by a shell-type stamping method generally used for thin ball bushing bearings, it is formed of a material with a wall thickness of 1 mm or less. The durability of the outer cylinder is maintained by quenching with a special heat treatment such as nitriding, so that grinding of the inner and outer diameters is not required after heat treatment, and the production efficiency of the ball bushing is improved.

[0022] However, with the adoption of an outer cylinder with a thin wall thickness for the sake of production simplification, it is difficult to maintain the accuracy of the roundness of the outer diameter dimension as a single body. Therefore, the inner diameter accuracy of the bushing hole of the cylinder body into which the ball bushing is inserted is improved. That is, since the accuracy of the ball bushing is affected by the inner peripheral surface of the bushing hole, it is necessary to machine the inner peripheral surface of the bushing hole with high precision as described above.

[0023] On the other hand, when inserting the thin ball bushing into the bushing hole, since a press-fit allowance is provided between the inner diameter of the bushing hole and the bushing is fixed by being forcibly press-fitted with a manual press, the accuracy after assembly is unstable, and the inner diameter tolerance of the ball bushing cannot maintain a high accuracy. In addition, once the press-fitted ball bushing is not easily replaceable, even if the ball bushing can be removed from the bushing hole, the press-fit allowance will disappear and it cannot be used again. The present disclosure is completed in view of such technical problems and can provide a cylinder that does not require high-precision machining of the inner diameter dimension of the bushing hole of the cylinder body.

[0024] The cylinder 40 of the present utility model will be described below with reference to the drawings. As Figure 1 shown, the cylinder 40 includes an annular ball bushing 10. The ball bushing 10 of the present embodiment is disposed between a rod 22 as a shaft member and a cylinder body 24. The ball bushing 10 guides the rod 22 to be movable relative to the cylinder body 24. A bushing hole 24A serving as a space for accommodating the ball bushing 10 is formed in the cylinder body 24. An outer cylinder 12 serving as an outer frame of the ball bushing 10 is disposed in the bushing hole 24A.

[0025] Figure 2A The outer cylinder 12 shown is formed in a cylindrical shape from a metal material such as bearing steel. As Figure 3 and Figure 8 shown, a plurality of concave portions 12A (six in the present embodiment) are provided at equal intervals in the circumferential direction of the inner peripheral surface of the outer cylinder 12. An arcuate joint surface 12B is provided in a portion between the adjacent concave portions 12A on the inner peripheral surface of the outer cylinder 12. As Figure 4A and Figure 4B shown, a synthetic resin-made retainer (holding member) 14 is disposed in the outer cylinder 12. The retainer 14 is formed in a cylindrical shape. Six convex portions 14A that cooperate with the concave portions 12A are provided on the outer peripheral surface of the retainer 14. These convex portions 14A are located at equally spaced positions in the circumferential direction of the retainer 14.

[0026] In addition, an arcuate engagement surface 14B is formed on the outer peripheral surface of the retainer 14 corresponding to the joint surface 12B of the outer cylinder 12. A groove portion 16 is provided in the retainer 14, and the groove portion 16 holds a plurality of steel balls 18 as a plurality of metal balls. Six groove portions 16 are arranged in a manner that straddles between the convex portions 14A and the engagement surface 14B. Each groove portion 16 is formed in an oval shape on the outer peripheral side in the axial direction of the retainer 14. Each groove portion 16 penetrates the inner and outer peripheral surfaces of the retainer 14.

[0027] Therefore, the joint surface 12B of the outer cylinder 12 and the engagement surface 14B of the retainer 14 are tightly fitted. The positioning of the retainer 14 in the rotational direction relative to the outer cylinder 12 is determined by the engagement of the concave portions 12A and the convex portions 14A, and relative rotation is not easy.

[0028] On the other hand, as Figure 2A and Figure 2B shown, the multiple steel balls 18 have the same outer diameter with respect to each other. When the outer diameter of the rod 22 is, for example, 16 mm, the outer diameter of the steel balls 18 is 2.381 mm. In this case, since the outer diameter of the multiple steel balls 18 is 14.88% with respect to the outer diameter of the rod 22, the outer diameter of the steel balls 18 is 18% or less with respect to the outer diameter of the rod 22.

[0029] In addition, grease or the like for smoothing the rotation of the steel balls 18 is enclosed in the multiple groove portions 16. Seals 20 for sealing the grease or the like in the groove portions 16 are respectively fitted into the annular grooves 12C formed at both end portions of the outer cylinder 12 with the retainer 14 interposed therebetween. Thus, the ball bushing 10 of the present embodiment shown in Figure 3 is completed.

[0030] In addition, as Figure 5 shown, different from the above, similar to the conventional thin ball bushing, even when the overall length L1 of the ball bushing 10 is longer than the overall length L0 of the bushing hole 24A, by respectively disposing snap rings 34 at both ends, the ball bushing 10 of the above-described embodiment can be used. In addition, the bushing hole 24A may not be used.

[0031] Next, the operation of the ball bushing 10 of the present embodiment will be described. The ball bushing 10 of the present embodiment is disposed between the rod 22 and the cylinder body 24, and guides the rod 22 so as to be movable relative to the cylinder body 24. In addition, the ball bushing 10 has a metal outer cylinder 12 in the bushing hole 24A formed in the cylinder body 24, and the outer cylinder 12 is formed in a cylindrical shape and disposed. On the inner peripheral surface of the outer cylinder 12, a plurality of concave portions 12A are formed at equal intervals in the circumferential direction of the outer cylinder 12. Between the adjacent concave portions 12A on the inner peripheral surface of the outer cylinder 12, an arc-shaped joint surface 12B is provided.

[0032] In addition, a cylindrical retainer 14 is disposed inside the outer cylinder 12. On the outer peripheral surface of the retainer 14, engagement surfaces 14B that engage with the joint surface 12B are provided at equal intervals in the circumferential direction of the retainer 14. The groove portions 16 for holding the multiple steel balls 18 are provided in the retainer 14 so as to penetrate the inner and outer peripheral surfaces. At this time, as described above, with respect to the outer diameter of these multiple steel balls 18 being 2.381 mm and the outer diameter of the rod 22 being 16 mm, the outer diameter of the multiple steel balls 18 is 18% or less with respect to the outer diameter of the rod 22.

[0033] Along with this, since the convex portions 14A that engage with the concave portions 12A on the inner peripheral surface of the outer cylinder 12 are provided between adjacent engaging portions, the engaging portions of the retainer 14 are tightly fitted to the joint surface 12B of the outer cylinder 12. Therefore, compared with conventional outer cylinders, the outer diameter can be relatively reduced, and the outer peripheral surface of the outer cylinder 12 does not need to be in contact with the inside of the bushing hole 24A of the cylinder body 24. As a result, when the ball bushing 10 is inserted into the bushing hole 24A of the cylinder body 24, press-fitting is not required either.

[0034] As described above, in the ball bushing 10 according to the present embodiment, the groove portion 16 penetrates the inner and outer peripheral surfaces of the retainer 14, so a part of the steel balls 18 protrudes from the inner peripheral surface of the retainer 14. Along with this, the inner diameter dimension D of the inscribed circle that connects the portions on the rod 22 side of the plurality of steel balls 18 in the free state Figure 2A shown is also maintained after being inserted into the bushing hole 24A of the cylinder body 24. Thus, it is not necessary to process the inner diameter of the bushing hole 24A, which is the space of the cylinder body 24, with high precision.

[0035] In addition, the outer cylinder 12 is made of metal, and the portion between adjacent concave portions 12A is an arc-shaped joint surface 12B. In addition, the engaging surface 14B of the retainer 14 in a state where the plurality of steel balls 18 are arranged in the groove portion 16 abuts against the arc-shaped joint surface 12B. Furthermore, by installing the seal 20, they can be reliably fitted together, and the small-sized ball bushing 10 is completed.

[0036] As described above, in the present embodiment, since small-sized steel balls 18 with an outer diameter of 18% or less relative to the outer diameter of the rod 22 are used, the outer diameter of the outer cylinder 12 can be more reliably reduced. As a result, not only can the miniaturization of the ball bushing 10 be achieved, but also the weight reduction can be achieved.

[0037] In addition, in a conventional ball bushing, if the outer diameter of the rod 22 is 16 mm, the outer diameter of the steel ball is 3.175 mm, and the outer diameter of the plurality of steel balls relative to the outer diameter of the rod 22 is 19.88%. That is, when it exceeds 18%, the sufficient weight reduction effect of the ball bushing cannot be achieved, and steel balls 18 with an outer diameter of 18% or less relative to the outer diameter of the rod 22 need to be used.

[0038] As a result of the above, by changing the inner diameter shape of the outer cylinder 12 or making the steel balls 18 have a small diameter, the outer diameter of the outer cylinder 12, which is the outer diameter of the ball bushing 10, is about 15% smaller than the outer diameter of the conventional ball bushing in the present embodiment.

[0039] In addition, in a conventional ball bushing, since the number of rows for holding the steel balls 18 is generally as Figure 6BAs shown, it has four columns, so sometimes the load P applied during actual use is applied to the steel balls 18 in a single column. In contrast, in the ball bushing 10 of the present embodiment, by increasing the groove portion 16 that holds a plurality of steel balls 18 to six columns, as shown in Figure 6A During actual use as shown, loads such as P1, P2, and P3 are dispersed, and thus the load can also be dispersed. Moreover, compared with the prior art, the outer cylinder 12 of the ball bushing 10 of the present embodiment not only has a thick wall and high strength, but also has no opening portion on the outer peripheral surface of the outer cylinder 12 that sometimes exists on the outer peripheral side of the outer cylinder 12 in the prior art. Therefore, there is no need to worry about garbage invading the ball bushing 10.

[0040] Next, the manufacturing method of the ball bushing 10 of the present embodiment will be described. When manufacturing the ball bushing 10 of the present embodiment, first, a cylindrical member 32 having a size matching the outer cylinder 12 of the size to be manufactured is cut to a necessary length. The cylindrical member 32 is a cylindrical special-shaped pipe member having Figure 7A The inner peripheral surface 32A of the shown polygon and is made of bearing steel.

[0041] Then, after the cut cylindrical member 32 is subjected to general oil quenching, the outer diameter is ground, and the portions protruding inward are ground and removed evenly and partially corresponding to the polygon on the inner peripheral surface side. As a result, as shown in Figure 8 The outer cylinder 12 having a plurality of concave portions 12A is individually and highly precisely machined and completed. Along with this, the inner peripheral surface portion between the mutually adjacent concave portions 12A formed into an arc shape by cutting becomes an arc-shaped joint surface 12B.

[0042] As a result, it is not necessary to improve the inner diameter accuracy of the inner peripheral surface of the bushing hole 24A, and the ball bushing 10 is not pressed into the bushing hole 24A. Therefore, the replacement of the ball bushing 10 can also be easily performed. That is, since it is not pressed into the bushing hole 24A, the ball bushing 10 can also be reused.

[0043] On the other hand, it has been found that when the cross-sectional area of the outer cylinder 12 made of a cylindrical special-shaped pipe material is less than 20% of the total cross-sectional area based on the outer diameter of the outer cylinder 12, it is affected by the inner diameter tolerance of the bushing hole 24A. Therefore, in the ball bushing 10 of the present embodiment, although the outer cylinder 12 has a cross-sectional area in a range of 20% or more, which is the limit value not affected by the inner diameter tolerance of the bushing hole 24A, the outer diameter dimension of the outer cylinder 12 is substantially the same as that of the conventional thin ball bushing. Moreover, with the determination of this limit value, the disadvantages of the conventional thin ball bushing are eliminated, which becomes a major feature of the ball bushing 10 of the present embodiment.

[0044] Specifically, due to the relationship with the inner diameter dimension of the bushing hole, two types of thin ball bushings were tested this time under the strict tight clearance K6 (tolerance when the inner diameter is 24 mm = 24.002 to 23.989 mm). First, based on the cylindrical member 32 of the present embodiment and the conventional simple annular cylindrical member 114 with substantially the same outer diameter, the A dimension of the thinnest part of the cylindrical member 32 shown in Figure 9A and the A dimension of the cylindrical member 114 shown in Figure 9B were measured respectively, and the data are shown in Table 1 below.

[0045] [Table 1]

[0046]

[0047] At this time, the total cross-sectional area of each outer diameter is 452.16 mm in the cylindrical member 32 of the present embodiment 2 (outer diameter 24.0 mm), and 455.93 mm in the cylindrical member 114 of the existing product 2 (outer diameter 24.1 mm). In addition, the respective wall thicknesses relative to each outer diameter are 2.8% in the cylindrical member 32 and 3.5% in 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 , which is larger than the cross-sectional area of the cylindrical member 114.

[0048] The ball bushing 10 of the present embodiment composed of the cylindrical member 32 and the two types of existing thin ball bushings composed of the cylindrical member 114 were respectively fitted between the bushing holes. Then, after the ball bushing 10 of the present embodiment was inserted into a bushing hole (not shown) machined and finished with an actual inner diameter of 23.989 mm in a tapping manner, the inner diameter dimension was confirmed with a go-no-go gauge. As a result, the go gauge entered and the no-go gauge could not enter, having no effect on the inner diameter of the ball bushing 10.

[0049] On the other hand, the inner diameter dimension of the conventional thin ball bushing formed by the cylindrical member 114 became smaller after being inserted into the bushing hole, and the go gauge could not enter, being unqualified as a product. That is, although the initial outer diameter of the cylindrical member 114 was 24.1 mm, as the outer diameter became smaller, the inner diameter also shrank, becoming a state that could not withstand actual use.

[0050] Regarding the above results, for the ratio of the cross-sectional area to the outer diameter, the cylindrical member 32 is 21.08%. In contrast, the cylindrical member 114 is 15.98% because the outer diameter shrank to about 24.0 mm. Only the cylindrical member 32 of the present embodiment entered the range of more than 20% which is the limit value. In addition, since the upper limit of the limit value is considered to be about 25%, the limit value can also be set to 20% to 25%.

[0051] Next, the retainer 14 is manufactured. The retainer 14 is made of synthetic resin and is produced by a forming die or the like. At this time, a plurality of convex portions 14A are formed on the outer peripheral surface of the retainer 14 in accordance with the positions of the plurality of concave portions 12A of the outer cylinder 12. In addition, corresponding to the arc-shaped joint surface 12B formed between the mutually adjacent concave portions 12A, an arc-shaped engaging surface 14B is also provided on the outer peripheral surface of the retainer 14. Further, a groove portion 16 is provided so as to straddle the arc-shaped engaging surface 14B and the convex portion 14A. A plurality of steel balls 18 are placed in the groove portion 16, and a lubricating grease or the like for smoothing the rotation of the steel balls 18 is sealed in the groove portion 16 for retention.

[0052] Then, the convex portion 14A on the outer peripheral surface of the retainer 14 holding the steel balls 18 is engaged with the concave portion 12A of the outer cylinder 12 and inserted into the outer cylinder 12. Along with this, the engaging portion of the retainer 14 formed in an arc shape corresponding to the joint surface 12B of the outer cylinder 12 is tightly fitted to the joint surface 12B. As a result, in the ball bushing 10 of the present embodiment, the convex portion 14A is engaged with the concave portion 12A to serve as a rotation stopper of the retainer 14, so that the outer diameter of the outer cylinder 12 can be reduced more reliably.

[0053] Further, the seal member 20 for sealing a lubricating grease or the like in the plurality of groove portions 16 is respectively fitted to both end portions of the outer cylinder 12 with the retainer 14 interposed therebetween. Thus, the ball bushing 10 of the present embodiment is completed as shown in Figures 2A to 3 shown. Finally, as shown in Figure 1 shown, by disposing the ball bushing 10 between the rod 22 and the cylinder body 24, the rod 22 can be guided by the ball bushing 10 so as to be movable relative to the cylinder body 24. At this time, the ball bushing 10 can also be positioned in the cylinder body 24 by a snap ring or the like.

[0054] Along with this, since the outer peripheral surface of the retainer 14 has the convex portion 14A that engages with the concave portion 12A of the inner peripheral surface of the outer cylinder 12, it is also possible that the outer diameter of the outer cylinder 12 is relatively reduced and the outer peripheral surface of the outer cylinder 12 does not contact the inside of the bushing hole 24A of the cylinder body 24. Therefore, when the ball bushing 10 is inserted into the bushing hole 24A of the cylinder body 24, press-fitting is not required.

[0055] As described above, according to the manufacturing method of the ball bushing 10 of the present embodiment, the inner diameter dimension D of the inscribed circle connecting the portions on the rod 22 side of the plurality of steel balls 18 in the free state is also maintained after being inserted into the bushing hole 24A of the cylinder body 24. Thus, a ball bushing 10 that does not require high-precision machining of the inner diameter dimension of the bushing hole 24A of the cylinder body 24 can be obtained. Figure 2A shown.

[0056] Next, the cylinder 40 assembled with the above-mentioned ball bushing 10 will be described. As Figure 10 shown, the cylinder 40 is a pneumatic cylinder driven by compressed air. Additionally, the cylinder 40 can also be an electric cylinder.

[0057] The cylinder 40 includes a cylinder main body 24, a piston 42, a piston rod 44, a plate 46, two ball bushings 10, and two rods 22.

[0058] The cylinder main body 24 is a metal main body. The cylinder main body 24 is formed in a rectangular parallelepiped shape, for example. The cylinder main body 24 extends in the Y direction. A cylinder bore 48 and two bushing holes 24A are formed in the cylinder main body 24. The cylinder bore 48 penetrates the central portion of the cylinder main body 24 in the X direction. The bushing holes 24A penetrate the cylinder main body 24 in the extending direction (X direction) of the cylinder bore 48. The two bushing holes 24A are located at positions that sandwich the cylinder bore 48 in the Y direction. A plurality of mounting holes 45 for fixing the cylinder main body 24 to a mounting target member (not shown) are formed in the cylinder main body 24.

[0059] One end portion (the end portion in the X1 direction) of the cylinder bore 48 is sealed by a top cover 50. The top cover 50 is airtightly mounted on the inner peripheral surface of the cylinder bore 48. An annular rod cover 52 is mounted at the other end portion (the end portion in the X2 direction) of the cylinder bore 48. The rod cover 52 is airtightly mounted relative to the inner peripheral surface of the cylinder bore 48.

[0060] The piston 42 is disposed in the cylinder bore 48. The piston 42 is located between the top cover 50 and the rod cover 52. The piston 42 slides along the axial direction (X direction) of the cylinder 40 relative to the inner peripheral surface of the cylinder bore 48. The piston 42 is airtightly in contact with the inner peripheral surface of the cylinder bore 48.

[0061] One end portion (the end portion in the X1 direction) of the piston rod 44 is connected to the central portion of the piston 42. The piston rod 44 passes through the central hole portion 54 of the rod cover 52. The other end portion (the end portion in the X2 direction) of the piston rod 44 is connected to the plate 46. A rod packing 56 is mounted between the outer peripheral surface of the piston rod 44 and the inner peripheral surface of the rod cover 52. The outer peripheral surface of the piston rod 44 is airtightly in contact with the rod packing 56.

[0062] A first cylinder chamber 58 is formed between the piston 42 and the top cover 50. A second cylinder chamber 60 is formed between the piston 42 and the rod cover 52.

[0063] The plate 46 extends in the extending direction (Y direction) of the cylinder main body 24. The piston rod 44 is connected to the central portion of the plate 46. The two ball bushings 10 are respectively mounted in a detachable state in the two bushing holes 24A provided in the cylinder main body 24. In other words, the ball bushings 10 are not press-fitted into the bushing holes 24A.

[0064] One end (the end in the X1 direction) of the outer cylinder 12 of the ball bushing 10 contacts or approaches a stepped portion 62 provided at one end of the bushing hole 24A. The other end (the end in the X2 direction) of the outer cylinder 12 of the ball bushing 10 contacts or approaches a retaining ring 64 mounted on the cylinder body 24. Thus, the ball bushing 10 is held relative to the cylinder body 24 in the axial direction of the cylinder 40. That is, the stepped portion 62 and the retaining ring 64 function as movement restricting portions that prevent the ball bushing 10 from moving axially along the outer cylinder 12 relative to the cylinder body 24.

[0065] Two rods 22 are respectively inserted into holes inside two ball bushings 10. The rods 22 extend in the axial direction (X direction) of the cylinder 40. A plurality of steel balls 18 of the ball bushing 10 roll along the outer peripheral surface of the rods 22. The two rods 22 are respectively connected to both end portions in the extending direction of the plate 46.

[0066] Next, the operation of the cylinder 40 will be described. When compressed air is supplied to the first cylinder chamber 58 while the second cylinder chamber 60 is open to the atmosphere, the piston 42 moves in the X2 direction. In addition, the plate 46 and the two rods 22 move in the X2 direction relative to the cylinder body 24 together with the piston 42. Thus, for example, an unillustrated workpiece can be pushed in the X2 direction by the plate 46. The rod 22 moves in the X2 direction relative to the ball bushing 10 mounted on the cylinder body 24, thereby guiding the plate 46 in the X2 direction. Thus, the plate 46 can move smoothly in the X2 direction.

[0067] When compressed air is supplied to the second cylinder chamber 60 while the first cylinder chamber 58 is open to the atmosphere, the piston 42 moves in the X1 direction. In addition, the plate 46 and the two rods 22 move in the X direction relative to the cylinder body 24 together with the piston 42. Thus, the plate 46 can be returned to its original position. The rod 22 moves in the X1 direction relative to the ball bushing 10 mounted on the cylinder body 24, thereby guiding the plate 46 in the X1 direction. Thus, the plate 46 can move smoothly in the X1 direction.

[0068] Next, the structure of the above-mentioned ball bushing 10 will be further described. As Figure 2A and Figure 2B shown, in the ball bushing 10, by inserting the convex portion 14A of the retainer 14 into the concave portion 12A of the outer cylinder 12, the rotation of the retainer 14 relative to the outer cylinder 12 is restricted. As Figure 2A shown, a plurality of concave portions 12A and convex portions 14A are provided at intervals in the circumferential direction of the outer cylinder 12. As Figure 3 shown, the concave portion 12A extends from one end of the outer cylinder 12 to the other end along the axial direction of the outer cylinder 12. The convex portion 14A extends from one end of the retainer 14 to the other end along the axial direction of the retainer 14.

[0069] As Figure 4BAs shown, a plurality of groove portions 16 are formed in the retainer 14. The plurality of groove portions 16 are formed at equal intervals in the circumferential direction of the retainer 14. A plurality of steel balls 18 are annularly arranged in the groove portions 16 so as to surround the central projection 15 provided in the groove portions 16. The groove portions 16 include a first opening portion 16a that opens to the outer peripheral surface of the retainer 14 and a second opening portion 16b that opens to the inner peripheral surface of the retainer 14. The size of the second opening portion 16b is smaller than the size of the first opening portion 16a.

[0070] The first opening portion 16a is formed to a size such that all of the plurality of steel balls 18 arranged in the groove portions 16 are in contact with the inner peripheral surface of the outer cylinder 12. The second opening portion 16b is formed to a size such that only a part of the plurality of steel balls 18 arranged in the groove portions 16 is in contact with the outer peripheral surface of the rod 22. That is, the retainer 14 has a wall portion 17 that covers a part of the plurality of steel balls 18 arranged in the groove portions 16 from the radially inner side of the retainer 14. Thus, by providing the wall portion 17 on the retainer 14, it is possible to suppress grease or the like sealed in the groove portions 16 from flowing out to the outside of the groove portions 16 via the second opening portion 16b.

[0071] In the above-described embodiment, the outer cylinder 12 and the plurality of steel balls 18 are made of metal, but for example, high-carbon chromium bearing steel can be considered. In addition, the retainer 14 is made of synthetic resin, but for example, polyoxymethylene resin can be considered. Further, as the material of the seal member 20, for example, rubber materials such as nitrile rubber can be considered. Moreover, the inner peripheral surface side of the cylindrical member 32 for manufacturing the outer cylinder 12 can be considered to be hexagonal, for example, but a cylindrical member having any shape from a triangle to a dodecagon can also be used.

[0072] On the other hand, since the diameter of the steel balls 18 is about 20% to 30% smaller than the conventional diameter, the number of the steel balls 18 is about 80% more than the conventional number. Along with this, the number of the groove portions 16 is also more than the conventional number. Further, in the present embodiment, a shaft member having an outer diameter of 16 mm of the shaft member is described, but for example, even for other outer diameters of shaft members such as 6 mm, 8 mm, 10 mm, 13 mm, 20 mm, etc., the present utility model can be applied.

[0073] In the ball bushing 10, as long as the rotation of the retainer 14 relative to the outer cylinder 12 can be restricted by inserting the convex portion 14A into the concave portion 12A, the number, shape, size, arrangement, etc. of the concave portion 12A and the convex portion 14A can be appropriately set. Specifically, for example, the length of the convex portion 14A in the axial direction of the retainer 14 may be shorter than the length of the concave portion 12A in the axial direction of the outer cylinder 12.

[0074] In the cylinder 40, the number of the bushing holes 24A and the ball bushings 10 may be one or three or more.

[0075] Regarding the above disclosure, the following remarks are also disclosed.

[0076] (Remark 1)

[0077] A cylinder includes: a cylinder main body in which a bushing hole is formed; an annular ball bushing disposed in the bushing hole; and a rod inserted into a hole inside the ball bushing. The ball bushing includes: an outer cylinder disposed in the bushing hole; a plurality of metal balls that are in contact with the outer peripheral surface of the rod in a state of being disposed inside the outer cylinder; and a cylindrical holding member for holding the plurality of metal balls. A recess is provided on the inner peripheral surface of the outer cylinder, and on the holding member are provided: a convex portion that restricts rotation of the holding member relative to the outer cylinder by being inserted into the recess; and a groove portion that penetrates from the outer peripheral surface to the inner peripheral surface of the holding member and in which the plurality of metal balls are disposed.

[0078] When the outer cylinder of the ball bushing is pressed into the bushing hole of the cylinder main body, rotation of the holding member relative to the outer cylinder is restricted by pressing the inner peripheral surface of the outer cylinder against the outer peripheral surface of the holding member. According to the cylinder described in Remark 1, since rotation of the holding member relative to the outer cylinder is restricted by inserting the convex portion into the recess, the outer cylinder of the ball bushing may not be pressed into the bushing hole of the cylinder main body. In this case, the ball bushing can be designed without considering deformation of the outer cylinder and the holding member caused by pressing the outer cylinder into the bushing hole. That is, there is no need to provide a press-fit margin on the outer cylinder. Therefore, compared with the case of pressing the outer cylinder into the bushing hole, the outer diameter of the outer cylinder can be reduced. In other words, the ball bushing can be miniaturized. In addition, since the ball bushing does not need to be pressed into the bushing hole, the inner diameter of the ball bushing can be maintained constant before and after inserting the ball bushing into the bushing hole. That is, the size (inner diameter dimension) of the inscribed circle connecting the portions of the plurality of metal balls in the free state that are in contact with the outer peripheral surface of the rod is also maintained after inserting the ball bushing into the bushing hole. Thus, there is no need to precisely machine the inner diameter dimension of the bushing hole of the cylinder main body. Furthermore, since the ball bushing does not need to be pressed into the bushing hole, in the case of damage to the ball bushing, only the ball bushing can be replaced.

[0079] (Remark 2)

[0080] In the cylinder described in Remark 1, it may also be provided with a movement restricting portion that prevents the ball bushing from moving axially along the outer cylinder relative to the cylinder main body.

[0081] According to such a structure, when the cylinder is in use, the movement restricting portion can prevent the ball bushing from coming out of the bushing hole.

[0082] (Remark 3)

[0083] In the cylinder described in Supplementary Note 1 or 2, it is also possible that a plurality of the concave portions and the convex portions are provided at intervals in the circumferential direction of the outer cylinder.

[0084] According to such a structure, it is easy to restrict the rotation of the holding member relative to the outer cylinder.

[0085] (Supplementary Note 4)

[0086] In the cylinder described in Supplementary Note 3, it is also possible that the outer cylinder is made of metal, and an arc-shaped joint surface that contacts the outer peripheral surface of the holding member is provided between the mutually adjacent concave portions in the inner peripheral surface of the outer cylinder.

[0087] According to such a structure, by bringing the joint surface of the outer cylinder into contact with the outer peripheral surface of the holding member, a cylinder having a small ball bushing can be obtained.

[0088] (Supplementary Note 5)

[0089] In the cylinder described in any one of Supplementary Notes 1 to 4, it is also possible that the concave portion extends from one end of the outer cylinder to the other end along the axial direction of the outer cylinder.

[0090] (Supplementary Note 6)

[0091] In the cylinder described in Supplementary Note 5, it is also possible that the convex portion extends from one end of the holding member to the other end along the axial direction of the holding member.

[0092] (Supplementary Note 7)

[0093] In the cylinder described in any one of Supplementary Notes 1 to 6, it is also possible that the retainer has a wall portion that covers a part of the plurality of metal balls arranged in the groove from the radially inner side of the holding member.

[0094] According to such a structure, it is possible to suppress the lubricant such as grease enclosed in the groove portion from flowing out more radially inward than the holding member.

[0095] (Supplementary Note 8)

[0096] In the cylinder described in any one of Supplementary Notes 1 to 7, it is also possible that the outer diameter of the plurality of metal balls is 18% or less relative to the outer diameter of the rod.

[0097] According to such a structure, since the outer diameter of the outer cylinder can be reduced, the ball bushing can be made small and lightweight. In addition, by making the ball bushing small and lightweight, the cylinder can also be made small and lightweight.

[0098] Although the present utility model has been described in detail, the present utility model is not limited to the above-described various embodiments. Within the scope not departing from the gist of the present utility model, or within the scope not departing from the gist of the present utility model derived from the content recited in the claimed scope and its equivalents, various additions, substitutions, changes, partial deletions, etc. can be made to these embodiments. In addition, these embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each action and the order of each process are shown as an example, but are not limited to these. Additionally, the same applies when numerical values or mathematical formulas are used in the description of the above-described embodiments.

Claims

1. A cylinder, characterized in that: have: a cylinder body, the cylinder body being formed with a bushing hole; an annular ball bushing disposed in the bushing hole; as well as a rod which is inserted into the hole on the inner side of the ball bushing, The ball bushing comprises: an outer cylinder, the outer cylinder being disposed in the bushing hole; a plurality of metal balls which are arranged in the outer tube and are in contact with the outer peripheral surface of the rod; and a cylindrical holder for holding the plurality of metal balls, A recess is provided on the inner circumferential surface of the outer cylinder. The retaining member is provided with: a convex portion that restricts rotation of the holder relative to the outer cylinder by being inserted into the concave portion; and A groove portion penetrates from the outer peripheral surface to the inner peripheral surface of the retainer and is used to arrange the plurality of metal balls.

2. The cylinder according to claim 1, characterized in that: A movement restricting portion is further provided, the movement restricting portion preventing the ball bushing from moving relative to the cylinder body in the axial direction of the outer tube.

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