JP2012255552A - Rolling bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling bearing, which is capable of well maintaining lubricating condition, which has high reliability, and capable of enhancing the life of the bearing.SOLUTION: The holder 114 of the rolling bearing is formed of a resin composition containing 10 to 40 wt.% of an inorganic fiber material in which tensile strength is 2 GPa or more and tensile elastic modulus is 50 Gpa or more. Further, the inorganic fiber material is at least one selected from para aramid fiber, polyarylate fiber, polyparaphenylene benzobisoxazole (PBO) fiber and is treated with a sizing agent.

Description

  The present invention relates to a rolling bearing for an outer ring guide that supports a rotating shaft and has a cage made of synthetic resin.

  Conventionally, a cylindrical roller bearing, an angular ball bearing, or the like is generally used as a rolling bearing that supports a main shaft of a machine tool. These rolling bearing cages include cages made by cutting phenolic resin reinforced with cotton cloth, 66 nylon resin reinforced with glass fiber or carbon fiber, polyphenylene sulfide resin, and polyether ether ketone resin. A so-called synthetic resin cage is used.

  Since the synthetic resin cage is lightweight, it has a small centrifugal force during rotation and is self-lubricating, which is advantageous for high-speed rotation. In rolling bearings for high speed rotation using these synthetic resin cages, an outer ring guide type in which the cage is normally guided by a bearing outer ring is employed. In addition, grease lubrication, oil-air lubrication, jet lubrication, etc. are appropriately employed depending on the use conditions and cost as lubrication methods for these rolling bearings. However, in general, grease is lubricated because of low cost and easy maintenance. Lubrication is often used.

  Here, in recent years, in machine tools, there is a tendency to improve the cutting ability and shorten the machining time, and accordingly, the tendency to increase the rotational speed of the spindle is remarkable. For this reason, the amount of lubricating oil supplied to the rolling bearing that supports the main shaft rotating at high speed also tends to be a very small amount (minimum required amount).

  However, if the lubricating oil is not supplied from the outside to the inside of the bearing during rotation, as in grease lubrication, the lubricating oil film tends to break off temporarily or continuously due to the passage of time. End up. Under such severe lubrication conditions, it is difficult to maintain a sufficient lubrication state. For this reason, the sliding portions between the cage, the rolling elements, and the inner and outer rings generate heat and become high temperature.

  Such a problem often occurs in a sliding portion between the outer ring guide surface and the cage and a sliding portion between the cage and the rolling element. When the wear of the synthetic resin cage progresses due to this sliding, the reinforcing fiber material such as glass fiber or carbon fiber is gradually exposed on the surface, and the other outer ring guide of the other party is exposed by the exposed reinforcing fiber material. It is assumed that the wear of the surface proceeds, and there is a possibility that the rolling bearing has a problem.

  The present invention has been made to eliminate such inconveniences, and an object of the present invention is to provide a rolling bearing capable of maintaining a good lubrication state, having high reliability and improving bearing life. It is to provide.

The above object of the present invention can be achieved by the following constitution.
(1) An outer ring guide type rolling bearing that supports a rotating shaft and has a synthetic resin cage, and the cage is an organic fiber material having a tensile strength of 2 GPa or more and a tensile elastic modulus of 50 GPa or more. The organic fiber material is at least one selected from para-aramid fibers, polyarylate fibers, and polyparaphenylenebenzbisoxazal (PBO) fibers. A rolling bearing characterized by being treated with a sizing agent.
(2) The rolling bearing according to (1), wherein the sizing agent is at least one selected from a urethane resin, an epoxy resin, an acrylic resin, and a bismaleimide resin.
(3) The rolling bearing according to (1) or (2), further comprising an outer ring and an inner ring, wherein the material of the outer ring and the inner ring is SUJ2 (bearing steel).

  According to the rolling bearing of the present invention, the cage is formed of a resin composition containing 10 to 40% by weight of an organic fiber material having a tensile strength of 2 GPa or more and a tensile modulus of 50 GPa or more. Therefore, it is possible to obtain a cage that is not damaged and has flexibility. As a result, even if the reinforcing fiber material is exposed from the cage, it is possible to prevent the outer ring guide surface from being worn by the cage, so that the lubrication state of the bearing can be maintained well, and the reliability is high. The bearing life can be improved.

It is principal part sectional drawing for demonstrating 1st Embodiment of the rolling bearing which concerns on this invention. It is a perspective view for demonstrating the holder | retainer shown in FIG. It is principal part sectional drawing for demonstrating 2nd Embodiment of the rolling bearing which concerns on this invention. It is a perspective view for demonstrating the holder | retainer shown in FIG.

  Hereinafter, each embodiment of the rolling bearing according to the present invention will be described in detail with reference to the drawings.

(First embodiment)
First, with reference to FIG.1 and FIG.2, 1st Embodiment of the rolling bearing which concerns on this invention is described.

  As shown in FIG. 1, a cylindrical roller bearing 110 that is a rolling bearing of the present embodiment includes an outer ring 111 having an outer ring raceway surface 111a on an inner peripheral surface, an inner ring 112 having an inner ring raceway surface 112a on an outer peripheral surface, and an outer ring raceway. A plurality of cylindrical rollers (rolling elements) 113 disposed so as to be able to roll between the surface 111a and the inner ring raceway surface 112a, and a retainer 114 that holds the plurality of cylindrical rollers 113 at substantially equal intervals in the circumferential direction; .

  The retainer 114 is an outer ring guide type that is rotationally guided by the inner peripheral surface of the outer ring 111, and as shown in FIG. 2, a pair of annular portions 115 that are coaxially spaced apart from each other in the axial direction, and a pair of A cylindrical roller 113 is formed between a plurality of column portions 116 arranged at substantially equal intervals in the circumferential direction and the respective column portions 116 adjacent to each other in the circumferential direction so as to connect the annular portions 115. And a pocket portion 117 that can be held.

  In the present embodiment, the cage 114 is an organic fiber material having a tensile strength of 2 GPa or more and a tensile modulus of 50 GPa or more, such as para-aramid fiber, polyarylate fiber, and polyparaphenylene shown in Table 1. It is formed of a resin composition containing 10 to 40% by weight of an organic fiber material such as benzbisoxal fiber. Further, in the present embodiment, the outer ring 111 is made of ordinary bearing steel, and the guide surface 111b that guides the cage 114 that is the inner peripheral surface of the outer ring 111 is hardened to protect the guide surface 111b. Is not given.

  Specific examples of the para-aramid fiber include polyparaphenylene terephthalamide and copolyparaphenylene-3,4'-oxydiphenylene terephthalate, which is obtained by copolymerizing diamine as a third component to improve stretchability. There is phthalamide. The polyarylate fiber is a wholly aromatic polyester fiber that is a polycondensate of a dihydric phenol and an aromatic dicarboxylic acid. PBO fiber is a polyparaphenylene benzbisoxazole (or polyparaphenylene benzobisoxal) fiber.

  Organic fiber materials having a tensile strength of 2 GPa or more and a tensile modulus of 50 GPa or more include ultra high molecular weight polyethylene in addition to para-aramid fibers, polyarylate fibers, and polyparaphenylene benzbisoxal fibers shown in Table 1. There are fibers and PAN-based carbon fibers. However, since the ultrahigh molecular weight polyethylene fiber has a melting point of about 140 ° C., it may be softened during use. Further, since the PAN-based carbon fiber is rigid, the PAN-based carbon fiber may damage an iron-based mating material, and is inferior in attenuation characteristics. Furthermore, meta-aramid fibers are not preferred for application due to insufficient strength.

  On the other hand, the para-aramid fiber, polyarylate fiber, and polyparaphenylene benzbisoxal fiber shown in Table 1 have high strength and flexibility, and have excellent attenuation characteristics of the fiber itself. When the organic resin material is incorporated into the base resin, the attenuation characteristics of the entire synthetic resin reinforcing material can be remarkably improved, and sliding noise can be reduced.

  In this embodiment, the para-aramid fiber, polyarylate fiber, and polyparaphenylene benzbisoxazal fiber shown in Table 1 are made of urethane resin, epoxy on the fiber surface in order to improve adhesion to the base resin. It is treated with at least one sizing agent selected from a resin, an acrylic resin, and a bismaleimide resin.

  The fiber diameter of the organic fiber material is preferably 6 to 21 μm, more preferably 8 to 15 μm, in terms of average diameter. When the average diameter of the organic fiber material is less than 6 μm, the fiber diameter is too thin and the strength per one is low, and stable production is difficult and practicality is low. On the other hand, if the average diameter of the organic fiber material exceeds 21 μm, the strength per fiber increases, but the fibers are thicker and the number of fibers decreases, making it difficult to uniformly reinforce the entire cage 114. It is not preferable.

  It is preferable in terms of strength that the length of the organic fiber material exists as long as possible in the cage 114. In that respect, the pellets used for injection molding of the cage 114 are organic compared to short fiber pellets (pellet length: about 3 mm) in which short fibers (chopped strands) of about 1 to 3 mm of organic fiber material are randomly dispersed. In the cage 114 obtained by injection molding, the organic fiber material is present in a longer state when the long fiber pellet (the pellet length is 7 to 11 mm) in which the fiber material is oriented parallel to the pellet is used. It is possible to reduce the manufacturing cost as well as being high in strength and suitable.

  Note that a part of the organic fiber material shown in Table 1 may be mixed with a high heat-resistant organic fiber material that has no damage to the iron-based material and has low strength but excellent heat resistance. Specifically, polyphenylene sulfide (PPS) fiber, polyimide (PI) fiber, and the like.

  The content of the organic fiber material in the resin composition forming the cage 114 is 10% by weight or more and 40% by weight or less, more preferably 15% by weight or more and 30% by weight or less of the entire resin composition. When the content of the organic fiber material is less than 10% by weight, the mechanical strength cannot be improved so much and the practicality as a cage is low. On the other hand, when the content of the organic fiber material exceeds 40% by weight, it becomes difficult to sufficiently secure the fluidity of the resin composition at the time of melt molding. When molding by injection molding or the like, productivity is affected. Unfavorable.

  In addition, as the base resin of the resin composition forming the cage 114, a thermoplastic resin having a certain level of heat resistance can be used. Further, in order to satisfy the fatigue resistance required for the cage 114, a crystalline resin is suitable. Specifically, polyamide resin, polyphenylene sulfide (PPS) resin, polyether ether ketone (PEEK) resin, etc. It is.

  As the polyamide resin, in addition to the aliphatic polyamide resin containing many amide bonds in the molecular structure excellent in fatigue resistance such as polyamide 6, polyamide 66, polyamide 46, etc., when priority is given to suppressing dimensional changes due to water absorption, It is more preferable to use a lower water-absorbing aromatic polyamide resin or an aliphatic polyamide having a less amide bond in the molecular structure, so-called high nylon. As high nylon, polyamide 610, polyamide 612, etc. having a melting point of 200 ° C. can be suitably used. As the aromatic polyamide resin, modified polyamide 6T such as polyamide 6T / 6I, polyamide MXD6, polyamide 9T, polyamide 4T and the like can be used.

  In addition to the organic fiber material shown in Table 1, an additive for preventing thermal deterioration of the resin may be added separately. Examples of the additive include amine-based antioxidants, phenol-based antioxidants, copper iodide-potassium iodide-based heat stabilizers, and the like. Among these, amine-based antioxidants and copper iodide-potassium iodide-based heat stabilizers are more suitable because they have a large effect of improving heat resistance.

  As described above, according to the rolling bearing 110 of the present embodiment, the cage 114 contains 10 to 40% by weight of an organic fiber material having a tensile strength of 2 GPa or more and a tensile elastic modulus of 50 GPa or more. Since it is formed by a thing, it can obtain the holder | retainer 114 which does not have a damage property with respect to a metal material, and has a softness | flexibility. Thereby, even if the organic fiber material, which is a reinforcing fiber material, is exposed from the cage 114, wear of the guide surface 111b of the outer ring 111 by the cage 114 can be prevented, so that the lubrication state of the bearing 110 is good. Therefore, it is possible to maintain high reliability and to improve the bearing life. Further, since an organic fiber material having a density lower than that of the glass fiber is used, the weight of the cage 114 can be reduced. Further, since an organic fiber material that is softer than the outer ring 111 made of bearing steel is used, the hardening process of the guide surface 111b of the outer ring 111 can be omitted, and the manufacturing cost can be reduced.

(Second Embodiment)
Next, with reference to FIG.3 and FIG.4, 2nd Embodiment of the rolling bearing which concerns on this invention is described.

  As shown in FIG. 3, an angular ball bearing 120, which is a rolling bearing of this embodiment, includes an outer ring 121 having an outer ring raceway surface 121a on an inner peripheral surface, an inner ring 122 having an inner ring raceway surface 122a on an outer peripheral surface, and an outer ring raceway. A plurality of balls (rolling elements) 123 disposed so as to be able to roll between the surface 121a and the inner ring raceway surface 122a, and a cage 124 that holds the plurality of balls 123 at substantially equal intervals in the circumferential direction. Prepare.

  The retainer 124 is an outer ring guide type that is rotationally guided by the inner peripheral surface of the outer ring 121, and as shown in FIG. 4, a plate-shaped annular member 125 and the annular member 125 substantially in the circumferential direction. And a plurality of pocket portions 126 that are formed at equal intervals and hold the balls 123 in a rollable manner.

  And in this embodiment, the holder | retainer 124 is formed with the resin composition which contains 10 to 40 weight% of organic fiber materials whose tensile strength is 2 GPa or more and whose tensile elasticity modulus is 50 GPa or more. Further, the resin composition of the present embodiment is the same as the resin composition forming the cage 114 of the cylindrical roller bearing 110. Further, in the present embodiment, the outer ring 111 is made of ordinary bearing steel, and the guide surface 111b that guides the cage 114 that is the inner peripheral surface of the outer ring 111 is hardened to protect the guide surface 111b. Is not given.

  As described above, according to the rolling bearing 120 of the present embodiment, the cage 124 includes 10 to 40% by weight of an organic fiber material having a tensile strength of 2 GPa or more and a tensile elastic modulus of 50 GPa or more. Since it is formed by a thing, it can obtain the holder | retainer 124 which does not have a damage property with respect to a metal material, and has a softness | flexibility. Thereby, even if the organic fiber material that is the reinforcing fiber material is exposed from the cage 124, the wear of the guide surface 121b of the outer ring 121 by the cage 124 can be prevented, and the lubrication state of the bearing 120 is excellent. Therefore, it is possible to maintain high reliability and to improve the bearing life. Further, since an organic fiber material having a density lower than that of the glass fiber is used, the weight of the cage 124 can be reduced. Furthermore, since an organic fiber material that is softer than the outer ring 121 made of bearing steel is used, the hardening process of the guide surface 121b of the outer ring 121 can be omitted, and the manufacturing cost can be reduced.

  Next, in order to confirm the effect of the present invention, a rotation test was performed on the rolling bearings of Examples 1 to 4 and Comparative Examples 1 and 2. In addition, about the rolling bearing, the thing similar to the angular ball bearing shown in FIG. 3 was used.

The specifications of the angular ball bearings of Examples 1 to 4 and Comparative Examples 1 and 2 are as follows.
Test bearing: 65BNR10DBB (inner diameter φ65mm, outer diameter φ100mm, width 18mm, contact angle 18 °, 4-row combination)
Inner and outer ring materials: SUJ2 (Examples 1 to 4, Comparative Example 1), carbonitrided steel SHX (Comparative Example 2)
Cage material: See Table 2 below.
The long fiber para-aramid fiber in Table 2 is a sizing agent-treated copolyparaphenylene-3,4'-oxydiphenylene terephthalamide, fiber diameter 12 μm / fiber, fiber length 9 mm (pellet length) Therefore, the polyarylate fiber is a sizing agent-treated, Kuraray Vectran high strength type, fiber diameter of about 10 μm / fiber, and fiber length of 1 mm. The cages of Comparative Examples 4 and 5 were made of an L-PPS material containing 30% carbon fiber (Fortron 2130A1 made of polyplastics).
Rolling element: Si3N4
Built-in preload: 300N

(Test conditions)
(1) Test rotation speed: 15000 min-1
(2) Rotation time: 1000 hr
(3) Lubricating grease: MTE grease (Ba complex-ester oil grease)
(4) Measurement item: initial torque, wear state of outer ring guide surface after 1000 hr Table 3 shows the test results.

  As is clear from Table 3, Examples 1 to 4 show no wear, whereas Comparative Example 1 shows slight wear, so the cage contains the organic fiber material of the present invention. It has been found that by forming with the resin composition, the outer ring guide surface is not damaged and wear of the outer ring guide surface is prevented.

  Further, as apparent from Table 3, Examples 1 to 4 show no wear, whereas Comparative Example 2 shows little wear. Therefore, the cage is a resin containing the organic fiber material of the present invention. It has been found that by using the composition, even if an inexpensive ordinary bearing steel (SUJ2) is used for the inner and outer rings, an effect of reducing wear equivalent to that of carbonitrided steel, which is costly, can be obtained.

110 Cylindrical roller bearings (rolling bearings)
114 Cage 120 Angular contact ball bearing (rolling bearing)
124 Cage

Claims (3)

An outer ring guide type rolling bearing that supports a rotating shaft and has a cage made of synthetic resin,
The cage is formed of a resin composition containing 10 to 40% by weight of an organic fiber material having a tensile strength of 2 GPa or more and a tensile modulus of 50 GPa or more,
The organic fiber material is at least one selected from para-aramid fiber, polyarylate fiber, and polyparaphenylene benzbisoxal (PBO) fiber, and is treated with a sizing agent. bearing.   The rolling bearing according to claim 1, wherein the sizing agent is at least one selected from a urethane resin, an epoxy resin, an acrylic resin, and a bismaleimide resin. It further has an outer ring and an inner ring,
The rolling bearing according to claim 1 or 2, wherein a material of the outer ring and the inner ring is SUJ2 (bearing steel).

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