Solid lubrication rolling bearing

Abstract

To provide a solid lubrication rolling bearing that can extend a wear service life of a solid lubricant.SOLUTION: A solid lubrication rolling bearing (1) includes: an outer ring (2); an inner ring (4); a plurality of rolling elements (6) interposed between the outer ring (2) and the inner ring (4); and a solid lubricant (10) for separating the rolling elements (6) in a circumferential direction. The solid lubricant (10) is made by impregnating an aluminum phosphate into an electric graphite.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a solid-lubricated rolling bearing equipped with a solid lubricant for use in environments such as high temperatures and vacuums. [Background technology]

[0002] Solid-lubricated rolling bearings are used in high-temperature atmospheres, vacuum atmospheres, and the like where grease or lubricating oil cannot be used as a lubricant. As this type of solid-lubricated rolling bearing, those described in Patent Document 1 and Patent Document 2 are conventionally known. In both configurations, parts are used to separate the rolling elements and the solid lubricant in the circumferential direction, and the solid lubricant is interposed between the two rolling elements. When the solid lubricant slides against the rolling elements or raceways, the lubricant is transferred to the rolling elements or raceways, or lubricant powder is generated on the rolling elements or raceways to lubricate the inside of the bearing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6275433 [Patent Document 2] Patent No. 3550689 Summary of the Invention [Problem to be solved by the invention]

[0004] In the bearing of Patent Document 1, a generally U-shaped restricting member is used as a component for separating the rolling elements and the solid lubricant in the circumferential direction. In the bearing of Patent Document 2, a cage is used for sandwiching and housing the rolling elements and the solid lubricant as a component for separating the rolling elements and the solid lubricant in the circumferential direction. For this reason, in Patent Documents 1 and 2, it is difficult to make the diameter of the solid lubricant larger than that of the rolling elements, and there is a risk that the wear life of the solid lubricant will be shortened.

[0005] An object of the present invention is to provide a solid-lubricated rolling bearing capable of extending the wear life of the solid lubricant. [Means for solving the problem]

[0006] The solid-lubricated rolling bearing of the present invention is a solid-lubricated rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a solid lubricant that circumferentially spaces the rolling elements, and the solid lubricant is made of electrographite impregnated with aluminum phosphate.

[0007] According to this configuration, the surface hardness of the solid lubricant is increased by impregnating the electrographite with aluminum phosphate, which results in a lower friction coefficient and wear rate on the surface of the solid lubricant, thereby extending the life of the solid lubricant rolling bearing.

[0008] In the present invention, at least one of the inner ring, the outer ring, and the rolling elements may be made of steel that has been treated with a manganese phosphate coating. With this configuration, the effect of the manganese phosphate coating is that sufficient initial lubrication is achieved (good initial running-in) and the lubricant is retained on the raceway surface. This extends the life of the solid lubricated rolling bearing.

[0009] In the present invention, the volume ratio of the solid lubricant occupying the bearing internal space between the inner ring and the outer ring may be set to 40 to 60%, and the solid lubricant may be guided to at least one of the inner diameter surface of the outer ring or the outer diameter surface of the inner ring.

[0010] According to this configuration, the solid lubricant separates the rolling elements in the circumferential direction and is guided by at least one of the inner diameter surface of the outer ring or the outer diameter surface of the inner ring. In other words, the solid lubricant separates the rolling elements in the circumferential direction and holds them against the inner and outer rings. Therefore, it is possible to omit a restricting member that separates the rolling elements and the solid lubricant in the circumferential direction and a retainer that holds the rolling elements and the solid lubricant against the inner and outer rings. In this way, by omitting the restricting member and the retainer, the solid lubricant can be made large and the optimal volume ratio can be achieved. Specifically, the volume ratio of the solid lubricant in the bearing internal space between the inner ring and the outer ring is set to 40 to 60%. The life of the solid lubricant rolling bearing corresponds to the wear life of the solid lubricant. According to the above configuration, the volume ratio of the solid lubricant in the bearing internal space is higher than that of the conventional technology, so that the life of the solid lubricant rolling bearing is extended.

[0011] In the present invention, the solid lubricant may have a ring-shaped annular portion and a plurality of columnar portions extending axially from the annular portion and disposed at equal intervals in the circumferential direction, and a pocket portion for accommodating the rolling element may be formed between adjacent columnar portions. In this case, the distance between adjacent columnar portions in the circumferential direction, i.e., the pocket clearance, may be set to 1.02 to 1.10 times the diameter of the rolling element.

[0012] In this way, by optimizing the pocket clearance, both ease of assembly and rotation in a stable position are achieved, and the wear life of the solid lubricant can be extended. In particular, at the beginning of operation when lubrication is most severe before the lubricant is transferred to the rolling elements and inner / outer rings, or before lubricant powder is generated on the rolling elements and inner / outer rings, optimizing the pocket clearance suppresses the movement of the solid lubricant inside the bearing, enabling rotation in a stable position. This extends the wear life of the solid lubricant. Effect of the Invention

[0013] In the solid-lubricated rolling bearing of the present invention, the surface hardness of the solid lubricant is increased by impregnating the electrographite with aluminum phosphate, which results in a lower friction coefficient and wear rate on the surface of the solid lubricant, thereby extending the life of the solid-lubricated rolling bearing. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view showing a solid lubricant rolling bearing according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a perspective view showing the solid lubricating rolling bearing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view showing a solid-lubricated rolling bearing 1 according to a first embodiment of the present invention, and Fig. 2 is a perspective view thereof. The solid-lubricated rolling bearing 1 is used in a high-temperature atmosphere (e.g., 300°C to 350°C) or a vacuum atmosphere where grease or lubricating oil cannot be used as a lubricant.

[0016] The solid lubricated rolling bearing 1 shown in Fig. 1 includes an outer ring 2, an inner ring 4, and rolling elements 6 interposed between the outer ring 2 and the inner ring 4. In this embodiment, balls are used as the rolling elements 6. However, the rolling elements 6 are not limited to balls. In this embodiment, the number of rolling elements 6 is eight, but the number of rolling elements 6 is not limited to this.

[0017] In the following description, the terms "axial direction," "radial direction," and "circumferential direction" refer to the "axial direction," "radial direction," and "circumferential direction" of the bearing, respectively. Specifically, the axial direction of the central axis of the outer ring 2 and the inner ring 4 is defined as the "axial direction," and the direction perpendicular to the "axial direction" is defined as the "radial direction." Furthermore, the term "circumferential direction" refers to the direction along the circumference that goes around the central axis of the central axis of the outer ring 2 and the inner ring 4. The definitions of these directions will remain the same in the following description.

[0018] The outer ring 2, the inner ring 4, and the rolling elements 6 are, for example, high carbon chromium bearing steel (SUJ2) that has been subjected to manganese phosphate coating treatment. In this embodiment, the outer ring 2, the inner ring 4, and the rolling elements 6 are all made of steel that has been subjected to manganese phosphate coating treatment, but it is sufficient that at least one of the outer ring 2, the inner ring 4, and the rolling elements 6 is made of steel that has been subjected to manganese phosphate coating treatment.

[0019] A raceway surface 2aa along which the rolling elements 6 roll is formed on the inner diameter surface 2a of the outer ring 2. The raceway surface 2aa is a surface recessed radially outward from the inner diameter surface 2a and is located at the axial center of the inner diameter surface 2a. In addition, annular outer locking grooves 2ab, 2ab are formed on both axial ends of the inner diameter surface 2a of the outer ring 2.

[0020] A raceway surface 4aa along which the rolling elements 6 roll is formed on the outer diameter surface 4a of the inner ring 4. The raceway surface 4aa is a surface recessed radially inward from the outer diameter surface 4a and is located at the axial center of the outer diameter surface 4a. In addition, annular inner locking grooves 4ab, 4ab are formed on both axial ends of the outer diameter surface 4a of the inner ring 4.

[0021] The solid-lubricated rolling bearing 1 also has shields 8, 8 at both axial ends. The shields 8, 8 block the bearing internal space SP between the outer ring 2 and the inner ring 4 from both axial ends. In other words, the shields 8, 8 prevent foreign matter from entering the bearing internal space SP. The shield 8 is, for example, a plate material made of SPTE (tinplate) that has been treated with a manganese phosphate coating. However, the material, surface treatment, etc. of the shield 8 are not limited to this.

[0022] One end (upper end in FIG. 1) 8a of the shield 8 is supported by one of the inner and outer rings 4, 2, and the other end (lower end in FIG. 1) 8b is adjacent to the other. In this embodiment, one end (upper end in FIG. 1) 8a is engaged with the outer locking groove 2ab of the outer ring 2, and the other end (lower end in FIG. 1) 8b slides within the inner locking groove 4ab of the inner ring 4.

[0023] The solid-lubricated rolling bearing 1 further includes a solid lubricant 10. When the bearing rotates, the solid lubricant 10 slides against the rolling elements 6 and the inner and outer rings 4, 2, and the lubricant 10 is transferred to the rolling elements 6 and the inner and outer rings 4, 2, or lubricant powder of the lubricant 10 adheres to the rolling elements 6 and the inner and outer rings 4, 2 and is generated to lubricate the inside of the bearing.

[0024] The solid lubricant 10 of this embodiment is a lubricant in which electrographite is impregnated with aluminum phosphate. Electrographite has superior heat resistance compared to carbon graphite, and the impregnated aluminum phosphate appropriately suppresses wear of the lubricant, contributing to a long life of the bearing.

[0025] 2, the solid lubricant 10 is a so-called comb-shaped solid lubricant having a ring-shaped annular portion 12 and a plurality of columnar portions 14 extending axially from the annular portion 12 and arranged at equal intervals in the circumferential direction. Pocket portions 16 are formed between adjacent columnar portions 14, 14, and rolling elements 6 are housed in the pocket portions 16. In other words, the pocket portions 16 are provided in the same number as the rolling elements 6. Therefore, in this embodiment, eight columnar portions 14 and eight pocket portions 16 are provided.

[0026] In this way, the rolling elements 6 are spaced apart in the circumferential direction by the columnar portions 14 of the solid lubricant 10. In addition, pocket gaps 18 exist between the columnar portions 14 and the rolling elements 6. In other words, the distance (circumferential spacing) d2 between the columnar portions 14, 14 is greater than the diameter d1 (FIG. 1) of the rolling elements 6 (d2>d1). For example, the distance d2 between the columnar portions 14, 14 adjacent in the circumferential direction is set to 1.02 to 1.10 times the diameter d1 of the rolling elements 6 (1.02≦(d2 / d1)≦1.10).

[0027] In this embodiment, as shown in FIG. 1, the solid lubricant 10 is guided by the inner diameter surface 2a of the outer ring 2 and the outer diameter surface 4a of the inner ring 4. In detail, the outer diameter surface 10a of the solid lubricant 10 is guided by the inner diameter surface 2a of the outer ring 2, and the inner diameter surface 10b of the solid lubricant 10 is guided by the outer diameter surface 4a of the inner ring 4. In other words, the rolling elements 6 are positioned relative to the outer ring 2 and the inner ring 4 by the solid lubricant 10. That is, the solid lubricant 10 also functions as a retainer that holds the rolling elements 6. In this way, the solid lubricant 10 of this embodiment has both the function of separating the rolling elements 6 in the circumferential direction and the function of holding the rolling elements 6. This makes it possible to omit the parts that separate the rolling elements and the solid lubricant in the circumferential direction (hereinafter referred to as "separating parts") and the retainer.

[0028] In this embodiment, the solid lubricant 10 is guided by both the inner diameter surface 2a of the outer ring 2 and the outer diameter surface 4a of the inner ring 4, but it may be guided by only one of the inner diameter surface 2a of the outer ring 2 or the outer diameter surface 4a of the inner ring 4.

[0029] In this way, the omission of separating parts and a cage allows the solid lubricant 10 to be made larger. The life of a solid-lubricated rolling bearing corresponds to the wear life of the solid lubricant, and the larger the solid lubricant 10, the longer the wear life of the solid lubricant 10. In this embodiment, the volume ratio of the solid lubricant 10 to the volume of the bearing internal space SP between the outer ring 2 and the inner ring 4 is set to 40 to 60%. Here, the "volume of the bearing internal space SP" refers to the radial space between the outer ring 2 and the inner ring 4, and the volume of the ring-shaped space between both axial end faces of the bearing 1.

[0030] Next, the experimental results of this embodiment will be described. The bearing used in the experiment had a bearing designation of 6002 (JIS: Japanese Industrial Standards). In the verification of the solid lubricant, the bearing of this embodiment has an inner ring 4 and an outer ring 2 made of SUS440C, a shield 8 made of SUS304, rolling elements 6 made of Si3N4, and a solid lubricant 10 made of electrographite impregnated with aluminum phosphate. On the other hand, the bearing of the comparative example has the same inner ring, outer ring, rolling elements, and shield, but the solid lubricant is made of electrographite and is not impregnated with aluminum phosphate. The bearing was forcibly heated to 350°C, subjected to a radial load of 49 N, and rotated at a speed of 1000 min -1 The durability test was carried out and the lifespan of each lubricant was compared and evaluated. The results are shown in Table 1. The test was carried out multiple times and the average value was regarded as the lifespan.

[0031] [Table 1]

[0032] As is clear from Table 1, the electrographite alone had a high friction coefficient and wear rate of the lubricant, resulting in a short lifespan. On the other hand, the electrographite impregnated with aluminum phosphate had a low friction coefficient and wear rate due to the effect of aluminum phosphate, resulting in a long lifespan.

[0033] In the verification of the manganese phosphate coating, the bearing of this embodiment has an inner ring 4, outer ring 2 and rolling elements 6 made of SUJ2 with a manganese phosphate coating applied to the entire surface, a shield 8 made of SPTE, and a solid lubricant 10 made of electrographite impregnated with aluminum phosphate. On the other hand, the bearing of the comparative example has the same shield and solid lubricant, but the inner ring, outer ring and rolling elements are made of SUJ2 and are not coated with manganese phosphate. As in the verification of the solid lubricant, the bearing was forcibly heated to 350°C and tested at a radial load of 49 N and a rotational speed of 1000 min -1 The durability test was carried out and the lifespan of each lubricant was compared and evaluated. The results are shown in Table 2. The test was carried out multiple times and the average value was regarded as the lifespan.

[0034] [Table 2]

[0035] As is clear from Table 2, without the manganese phosphate coating, there was an initial lack of lubricant, which caused the raceway surface to become rough and the lubricant could not be retained on the raceway surface, resulting in a short life. On the other hand, with the manganese phosphate coating, the coating provided sufficient initial lubrication and the lubricant was retained on the raceway surface, resulting in a long life.

[0036] Table 3 shows the evaluation results of "life of solid lubricant 10" and "rotatability of bearing" when the size of solid lubricant 10, i.e., the volume ratio of solid lubricant 10 to the bearing internal space SP, is changed. In the table, "◯" means good and "×" means bad.

[0037] [Table 3]

[0038] In the example where the volume ratio was 20%, the solid lubricant 10 was small and had a short life. In addition, the rolling elements 6 could not be held sufficiently, so vibration was large and the rotational performance was not good. In the examples where the volume ratio was 40% and 60%, the life of the solid lubricant 10 was sufficient and the rotational performance of the bearing was also good. In the example where the volume ratio was 80%, the life of the solid lubricant 10 was sufficient, but the large solid lubricant 10 was likely to interfere with other parts and the rotational performance of the bearing was not good. Therefore, the volume ratio of the solid lubricant 10 in the bearing internal space SP is preferably 40 to 60%.

[0039] Table 4 shows the evaluation results of "bearing rotation performance" when the size of the pocket clearance 18, that is, the ratio (d2 / d1) of the distance d2 between the column portions 14, 14 to the diameter d1 of the rolling element 6, is changed. In the table, "◯" means good, "△" means somewhat good, and "×" means poor.

[0040] [Table 4]

[0041] When (d2 / d1) is less than 1.00, the pocket gap 18 is a "negative gap" example. When (d2 / d1) is less than 1.00, slippage occurs between the rolling element 6 and the solid lubricant 10, and the rotation performance is not good. When (d2 / d1) is 1.00 to 1.02, the rotation performance is not poor, but the pocket gap 18 is small, so the interference between the rolling element 6 and the solid lubricant 10 is large, and the rotation performance is not good. When (d2 / d1) is 1.02 to 1.10, the rotation performance is good. When (d2 / d1) is greater than 1.10, the pocket gap 18 is large, and the rolling element 6 moves through the large pocket gap 18, so vibration increases and the rotation performance is not good. Therefore, the size (d2 / d1) of the pocket gap 18 is preferably 1.02 to 1.10.

[0042] According to the above configuration, by impregnating the electrographite with aluminum phosphate, the hardness of the surface of the solid lubricant 10 is increased. As a result, the friction coefficient and wear rate of the surface of the solid lubricant 10 are reduced, and the life of the solid lubricant rolling bearing is extended.

[0043] Furthermore, the inner ring 4, the outer ring 2, and the rolling elements 6 are made of steel that has been treated with a manganese phosphate coating. Therefore, due to the effect of the manganese phosphate coating, sufficient initial lubrication is achieved (good initial running-in) and the lubricant is retained on the raceway surface. This extends the life of the solid-lubricated rolling bearing. Note that the same effect can be obtained when at least one of the inner ring 4, the outer ring 2, and the rolling elements 6 is made of steel that has been treated with a manganese phosphate coating.

[0044] The solid lubricant 10 separates the rolling elements 6 in the circumferential direction and is guided by the inner diameter surface 2a of the outer ring 2 and the outer diameter surface 4a of the inner ring 4. In other words, the solid lubricant 10 separates the rolling elements 6 in the circumferential direction and holds them against the inner and outer rings 4, 2. Therefore, it is possible to omit a spacing member that separates the rolling elements 6 and the solid lubricant 10 in the circumferential direction and a retainer that holds the rolling elements 6 and the solid lubricant 10 against the inner and outer rings 4, 2. In this way, by omitting the spacing member and the retainer, the solid lubricant 10 can be made large and the volume ratio can be optimized. The life of the solid lubricant rolling bearing 1 corresponds to the wear life of the solid lubricant 10. In the above configuration, the volume ratio of the solid lubricant 10 in the bearing internal space SP is higher than in the conventional technology, so that the life of the solid lubricant rolling bearing is extended.

[0045] In addition, the distance between the circumferentially adjacent column parts 14, 14, i.e., the pocket clearance 18, is set to 1.02 to 1.10 times the diameter of the rolling element 6. In this way, by optimizing the pocket clearance 18, both ease of assembly and rotation in a stable posture are achieved, and the wear life of the solid lubricant 10 can be extended. In particular, by optimizing the pocket clearance 18 at the beginning of operation when lubrication is the most severe before the lubricant 10 is transferred to the rolling element 6 or the inner and outer rings 4, 2, or before lubricating powder of the lubricant 10 is generated on the rolling element 6 or the inner and outer rings 4, 2, the movement of the solid lubricant inside the bearing is suppressed, and rotation in a stable posture is possible. This extends the wear life of the solid lubricant 10.

[0046] The present invention is not limited to the above-mentioned embodiment, and various additions, modifications, and deletions are possible without departing from the scope of the present invention. For example, in the above-mentioned embodiment, the example in which balls are used as the rolling elements 6 is described, but cylindrical rollers or tapered rollers may also be used. Therefore, such things are also included in the scope of the present invention. [Explanation of symbols]

[0047] 1. Solid lubricated rolling bearings 2 Outer ring 2a Inner diameter surface of outer ring 4. Inner Circle 4a Outside diameter surface of inner ring 6 Rolling elements 10 Solid Lubricants 12 Circular Ring 14 Pillar section 16 Pocket section SP Bearing internal space

Claims

1. A solid-lubricated rolling bearing comprising an inner ring, an outer ring, a plurality of rolling elements interposed between the inner ring and the outer ring, and a solid lubricant spaced apart from the rolling elements in a circumferential direction, The solid lubricant for the solid lubricant rolling bearing is made of electrographite impregnated with aluminum phosphate.

2. 2. A solid-lubricated rolling bearing according to claim 1, wherein at least one of said inner ring, said outer ring and said rolling elements is made of steel that has been treated with a manganese phosphate coating.

3. 3. The solid-lubricated rolling bearing according to claim 1, wherein a volume ratio of the solid lubricant occupying an internal space of the bearing between the inner ring and the outer ring is set to 40 to 60%, A solid-lubricated rolling bearing, wherein the solid lubricant is guided to at least one of an inner diameter surface of the outer ring or an outer diameter surface of the inner ring.

4. 4. The solid lubricant rolling bearing according to claim 3, wherein the solid lubricant has a ring-shaped annular portion and a plurality of columnar portions extending axially from the annular portion and disposed at equal intervals in a circumferential direction, A solid-lubricated rolling bearing in which a pocket portion for accommodating the rolling elements is formed between adjacent column portions.

5. 5. A solid-lubricated rolling bearing according to claim 4, wherein the distance between adjacent column portions in the circumferential direction is set to 1.02 to 1.10 times the diameter of the rolling elements.

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