WO2017098886A1

WO2017098886A1 - Rolling bearing

Info

Publication number: WO2017098886A1
Application number: PCT/JP2016/084197
Authority: WO
Inventors: 広道國米; 奈央林; 大地伊藤
Original assignee: Ntn株式会社
Priority date: 2015-12-10
Filing date: 2016-11-18
Publication date: 2017-06-15
Also published as: JP2017106559A

Abstract

The invention addresses the problem of providing a solid lubricant type rolling bearing that can be suitably used under radiation exposure and under low-temperature, low-vacuum environments, such as in outer space. A rolling bearing (1) comprises: an inner ring (2) in which a raceway (4) is formed on the outer circumferential face; an outer ring (3) in which a raceway (5) is formed on the inner circumferential face; a plurality of rolling elements (6) that are embedded between the raceways (4, 5) of the inner ring (2) and the outer ring (3); and a cage (7) that retains the rolling elements (6) at intervals in the circumferential direction and that contains a solid lubricating agent. The primary component of the cage (7) is polyethylene.

Description

Rolling bearing

The present invention relates to a rolling bearing that is suitably used under radiation exposure such as outer space and in a low-temperature and low-vacuum environment, and particularly relates to a rolling bearing that employs a solid lubrication system.

Bearings for space equipment such as rocket engines are often used in special environments such as vacuum / cryogenic environments, so lubricating oils and greases commonly used as bearing lubricants are not used. A self-lubricating film coating is applied to both or one of the wheels and rolling elements, and a solid lubrication method is adopted in which a solid lubricant is supplied to the raceway ring from the cage containing the solid lubricant via the rolling elements.

As a cage used in this solid lubrication type bearing, for example, it is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2002-130300) and the like, such as PTFE excellent in mechanical properties (strength and heat resistance). The main components are engineering plastics such as fluororesin and polyimide, and a solid lubricant such as molybdenum disulfide added thereto.

JP 2002-130300 A

However, when used in an environment that is exposed to radiation such as outer space for a long period of time, the radiation resistance of the bearing is also required, so PTFE has a problem of embrittlement against radiation. In addition, polyimide has a high molding temperature and it is not easy to add a solid lubricant, and has a problem in terms of high water absorption and dimensional change stability.

Therefore, the present invention is intended to provide a solid lubrication type rolling bearing that is suitably used under radiation exposure such as outer space and in a low temperature and low vacuum environment.

In order to solve the above problems, in the rolling bearing according to the present invention, an inner ring having a raceway surface formed on the outer peripheral surface, an outer ring having a raceway surface formed on the inner peripheral surface, and the inner ring and the outer ring are incorporated. In a rolling bearing provided with a plurality of rolling elements that are spaced apart in the circumferential direction, and a cage containing a solid lubricant,
The cage is mainly composed of polyethylene.

The solid lubricant may be molybdenum disulfide.

In the above-described configuration, it is preferable that a lubricant film of the same type as the solid lubricant is applied to at least one of the raceway surfaces of the inner ring and the outer ring and the rolling element surface. The inner ring and the outer ring are preferably made of martensitic stainless steel.

Also, the cage can be increased in strength by adding a fiber reinforcement.

The rolling bearing of this invention uses polyethylene as a main component and is composed of a cage containing a solid lubricant, realizing a solid lubrication type rolling bearing with excellent radiation resistance and dimensional stability. can do. Therefore, the rolling bearing of the present invention can be suitably used under radiation exposure such as outer space and in a low temperature and low vacuum environment.

It is sectional drawing of the rolling bearing of 1st Embodiment of this invention. It is a perspective view which shows the structure of the holder | retainer used for the rolling bearing of FIG. It is a partial expanded side view of the rolling bearing of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Hereinafter, a rolling bearing according to an embodiment of the present invention will be described with reference to the accompanying drawings. The rolling bearing according to this embodiment is a rolling bearing applied for use in a cryogenic environment such as outer space, and is used for, for example, an artificial satellite.

As shown in FIG. 1, the rolling bearing 1 includes an inner ring 2 having a raceway 4 on an outer peripheral surface 2 a, an outer ring 3 having a raceway 5 on an inner peripheral surface 3 a, a raceway 4 of the inner ring 2, and a raceway 5 of the outer ring 3. A radial deep groove ball bearing including a plurality of balls 6 which are a plurality of rolling elements interposed therebetween and a cage 7 which holds the plurality of balls 6 at intervals in the circumferential direction.

The inner ring 2, the outer ring 3, and the ball 6 can use normal bearing materials, for example, martensitic stainless steel can be used. Martensitic stainless steel is excellent in bearing applications because it has high strength and hardness and excellent wear resistance. The martensitic stainless steel preferably has a Rockwell hardness HRC of 56 or more.

The balls 6 may be ceramic balls. In the case of using ceramics, silicon nitride (Si ₃ N ₄ ), silicon carbide (SIC), alumina (AI ₂ O ₃ ), zirconia (ZrO ₂ ), sialon and the like can be mentioned.

The cage 7 is mainly composed of polyethylene resin and contains a solid lubricant. As the polyethylene resin, it is preferable to use ultrahigh molecular weight polyethylene, and it is particularly preferable to use a resin having excellent compression molding and high sliding characteristics. As an example, high-sliding special polyethylene manufactured by Mitsui Chemicals, Inc., trade name “Lubmer” (registered trademark), and ultrahigh molecular weight polyethylene “Miperon” (registered trademark) manufactured by Mitsui Chemicals, Inc. are preferably used. can do.

As the solid lubricant, graphite, tungsten disulfide or molybdenum disulfide can be used. In particular, molybdenum disulfide is gradually accelerated in a high temperature environment of 350 ° C or more, and is modified to molybdenum trioxide, which may cause loss of properties. As described later, it is blended in polyethylene with a low injection molding temperature. It can be suitably used as a solid lubricant.

Further, as shown in the following formula (1), molybdenum disulfide reacts with water to become molybdenum trioxide. Like oxidation, the reaction is accelerated in a high-temperature environment, and a material having high water absorption such as polyimide exposes the added molybdenum disulfide to water, which may further accelerate the reaction.
MoS ₂ + H ₂ O → MoO ₂ + 2H ₂ S
2MoO ₂ + O ₂ → 2MoO ₃

Further, the cage 7 can contain a fiber reinforcing material such as glass fiber or carbon fiber as a reinforcing material.

The cage 7 is made of 70 to 95% by volume of polyethylene resin, 5 to 30% by volume of solid lubricant, and 0 to 20% by volume of reinforcing material, and can be made by means such as compression molding or injection molding. The molding temperature is 300 ° C. or lower because the main component is polyethylene resin.

As shown in Table 1 below, the polyethylene resin that is the main component of the cage 7 of the present embodiment is inferior in mechanical properties (strength, heat resistance) to engineering plastics such as fluororesins such as PTFE and polyimide, but is resistant to resistance. It has radiation characteristics, low water absorption, and low molding temperature. In addition to the above properties, polyethylene is a material with self-lubricating properties, so it is made of polyethylene as the main component and solid lubricant added to bearings that are exposed to radiation and used in low-speed / low-temperature environments. Is preferably used in a vacuum / cryogenic environment and in an environment exposed to radiation.

As shown in FIG. 2, the cage 7 has a plurality of pockets 8 in which balls 6 are accommodated one by one, and in the illustrated example, 20 pockets 8 are provided at equal intervals in the circumferential direction. The ball 6 is held in contact with the pocket surface 8 a of each pocket 8 and held in the pocket 8. The cage 7 used in the rolling bearing 1 according to the present embodiment is an outer ring guide type cage whose radial position is guided by the inner peripheral surface 3 a of the outer ring 3.

Although not shown, the rolling bearing 1 is lubricated by a solid lubrication method. A solid lubricant or a lubricant is applied to at least one of the raceway 4 of the inner ring 2, the raceway 5 of the outer ring 3, and the surface of the ball 6. A solid lubrication layer is provided by the included composite. The solid lubricant is the same type of solid lubricant used in the cage, and graphite, tungsten disulfide or molybdenum disulfide is used. As described above, since the cage 7 contains a solid lubricant, an appropriate amount of lubricant is supplied to the

raceway surfaces

4 and 5 of the inner ring 2 and the outer ring 3 through the balls 6 that contact the pocket surface 8a during operation. The The surface roughness Ra of the surfaces of the

raceway surfaces

4 and 5 is preferably 0.1 μm or less.

As mentioned above, according to the ball bearing concerning this embodiment, since it is constituted using a cage containing polyethylene lubricant as a main ingredient and containing a solid lubricant, it is a solid excellent in radiation resistance performance and dimensional stability. A lubrication type rolling bearing can be realized. Therefore, the rolling bearing of the present invention can be suitably used under radiation exposure such as outer space and in a low temperature and low vacuum environment. In addition, since the polyethylene resin can be molded at a low molding temperature, the modification of the solid lubricant contained can be suppressed.

As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to the thing of embodiment shown in figure. Various modifications and variations can be made to the illustrated embodiment within the same range or equivalent range as the present invention.

In the above embodiment, the ball bearing is described. However, the present invention is not limited to the ball bearing. For example, an angular ball bearing, a four-point contact ball bearing, a self-aligning ball bearing, and a cylindrical roller bearing. It can be applied to various rolling bearings such as a tapered roller bearing and a self-aligning roller bearing.

1: Rolling bearing 2: Inner ring 2a: Inner ring outer peripheral surface 3: Outer ring 3a: Outer ring inner peripheral surface 4: Inner ring raceway 5: Outer ring raceway 6: Ball 7: Cage 8: Pocket 8a: Pocket surface

Claims

An inner ring having a raceway surface formed on the outer peripheral surface, an outer ring having a raceway surface formed on the inner peripheral surface, a plurality of rolling elements incorporated between the inner ring and the outer ring, and the rolling elements spaced circumferentially In a rolling bearing provided with a cage containing a solid lubricant,
A rolling bearing according to claim 1, wherein the cage is mainly composed of polyethylene.
The rolling bearing according to claim 1, wherein the solid lubricant is molybdenum disulfide.
The rolling bearing according to claim 1 or 2, wherein a lubricant film of the same kind as the solid lubricant is applied to at least one of the raceway surfaces of the inner ring and the outer ring and the surface of the rolling element.
The rolling bearing according to any one of claims 1 to 3, wherein the inner ring and the outer ring are made of martensitic stainless steel.
The rolling bearing according to any one of claims 1 to 4, wherein a fiber reinforcing material is added to the cage.