JP2931868B2 - Roller bearing cage - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a roller bearing retainer used in an environment where lubricating oil or grease cannot be used, such as in a vacuum, at a high temperature, at a low temperature, or under radiation.

[Conventional technology]

BACKGROUND ART Conventionally, there are the following three methods for lubricating rolling bearings of various devices operating in an environment where lubricating oil and grease cannot be used.

(1) Molybdenum disulfide (Mo) is applied to all or some of the sliding surfaces of the inner ring, outer ring, cage and rolling elements by sputtering or the like.
S _2), in a way to form a thin lubricant film, such as tungsten disulfide (WS ₂₎ and silver (Ag), JP typical examples thereof include
55-57717, JP-A-58-113629 and JP-A-61-55410.

(2) A cage made of a sintered alloy obtained by adding a solid lubricant such as MoS ₂ or WS ₂ to a metal or an alloy is used, and the material of the cage is replaced by the rolling element and the rolling element by friction between the rolling element and the cage. A method of forming a thin lubricating film by transferring to an inner ring and an outer ring through an intermediate ring, typical examples of which are disclosed in JP-A-62-151539 and JP-A-63-246507.
Is shown in

(3) A cage is formed using plastic or a polymer-based composite material obtained by adding a solid lubricant to plastic,
A method in which a cage material is transferred to an inner ring and an outer ring via a rolling element and a rolling element by friction between a rolling element and a cage to form a thin lubricating film. A typical example is a fluororesin-based Lulon E (Product name of NTN / Lulong) or Duroid
(Trade name of Barden, USA). Such a cage is formed by adding glass fiber and MoS ₂ to a polytetrafluoroethylene resin (hereinafter abbreviated as PTFE).

[Problems to be solved by the invention]

However, in the method of forming a thin lubricating film in advance as in the above (1), if the film is worn by friction, the lubricating effect is lost, and the metal of the base material is exposed and seizure occurs. It is.

The cage using a sintered metal as in (2) has poor machinability, has a large frictional noise, has a brittle defect, and has a problem that it breaks during use and wear in the atmosphere is extremely large.

In the method (3) using the polymer composite material,
When PTFE is reinforced with glass fiber, the lubricating material transferred from the cage is shaved off or the rolling element surface is roughened by the glass fiber that has protruded to the surface. There was a drawback that torque fluctuations were easily caused at times.

As a countermeasure, for example, as proposed in Japanese Patent Application Laid-Open No. 62-261718, a method of dissolving and removing glass fibers on the processing surface portion of the retainer with hydrofluoric acid has been adopted. Due to its toxicity, special care must be taken during handling. Even if such treatment is performed, if the abrasion of the PTFE progresses, glass fibers will eventually appear on the surface, which will adversely affect lubrication as before.

A cage using a polyimide having thermally stable characteristics as a polymer composite material other than PTFE has a disadvantage that a large amount of gas is released in a vacuum. Also,
As in 1989, cages composed of a composition composed of thermoplastic polyether aromatic ketone, fluororesin and aromatic polyamide fiber have the disadvantage that the friction coefficient fluctuates greatly, causing uneven wear, torque fluctuation and shaft runout. There is.

As described above, in the conventional cage made of a polymer-based composite material or a sintered material, wear of a portion to which a load is applied progresses quickly, and therefore, the supply of the lubricant to the inner and outer rings and the rolling elements is uniform. However, there is a problem that the torque is not stable, dust is increased, and the bearing life is shortened.

The present invention has been made in order to solve the above problems, and improves the lubricity by performing stable and uniform transfer, low torque, long life, low dust generation, low degassing,
An object of the present invention is to provide a low-noise, low-cost, easy-to-work rolling bearing retainer.

[Means for solving the problem]

Therefore, the present invention is a polytetrafluoroethylene resin
10 to 40% by weight, 5 to 30% by weight of aramid fiber, and one or both of molybdenum disulfide and tungsten disulfide
Roller bearing cages are made of a composite material of polyetheretherketone resin, with the balance being ~ 30% by weight.

Aramid fibers are arranged in the axial direction to reduce circumferential friction.

[Action]

Polyetheretherketone resin (hereinafter abbreviated as PEEK)
Is tough, has excellent heat resistance, and has self-lubricating properties.However, since it is difficult for the resin to transfer to the mating surface, there is little gas generation in vacuum, and low friction, low wear, and heat resistance are achieved. With PTFE, a layered solid lubricant that is easy to transfer to the mating surface
By adding one or both of MoS ₂ and WS _{2 in} an appropriate amount, transfer becomes easy and stable, and lubricity of the transferred film becomes good.

It should be noted that the hardness and strength reduction caused by the addition of these can be prevented by adding an aramid fiber which is a heat-resistant organic material. Since this aramid fiber has self-lubricating properties, it does not affect lubrication even when exposed to a friction surface like glass fiber. Although the coefficient of friction varies greatly with PTFE alone, the addition of one or both of MoS ₂ and WS ₂ can form a uniform and stable lubricating film and reduce the coefficient of friction fluctuation.

In addition, since aramid fibers are arranged in the axial direction,
Since the molded cage has no protrusion of the end face of the aramid fiber, the part where the circumferential pocket wall and the rolling element rub does not
Since the film transferred to the rolling elements is not scraped off, the bearing has a long life. Since aramid fibers are more excellent in machinability than glass fibers, the mixture can be injection-molded, extruded and compressed, and the processing cost is reduced.

Furthermore, since PEEK and the materials added to it all show low degassing properties in a vacuum, naturally the molded articles obtained also show low degassing properties.

〔Example〕

 Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

First, 60% by weight of PEEK powder, 20% by weight of commercially available PTFE powder, 10% by weight of aramid fiber having a length of 1 mm, and 10% by weight of MoS ₂ powder are each heated and dried at 150 ° C. for 3 hours, and then sufficiently mixed. And dried at 150 ° C. for 1 hour.

PEEK is a powder or pellet form sold by ICI of the United Kingdom (continuous use temperature 240 ° C, melting point 3
34 ° C) can be used.

This mixture was provided at the center of the annular outer peripheral surface of a mold (not shown) as shown in FIG. 1 under the conditions of a cylinder temperature of 360 ° C., a mold temperature of 380 ° C., an injection pressure of 1200 kg / cm ² , and a screw rotation speed of 120 rpm. Injection molding was performed from the radial runner 2 toward the cavity, and an annular molded product 1 was obtained. In this molded product, the aramid fibers 3 are arranged in the axial direction. This was taken out of the mold and heat-cured at 280 ° C. for 2 hours. Then, a pocket hole 6 was formed by machining, and an angular-type cage 5 corresponding to frame number # 608 shown in FIG. 2 was produced.

Next, the inner ring 8, the outer ring 9 and the rolling element 10 coated with a 0.5 μm MoS ₂ film by sputtering are combined to form a third
A ball bearing 7 as shown in FIG.

This ball bearing 7 was subjected to a durability test under the following conditions, and the motor torque during operation, the bearing life, and the wear amount of the cage were measured.

・ Ambient pressure (2-4) × 10 ^-7 Torr, in the air ・ Thrust load: 7kg ・ Bearing temperature: 120 ℃ ・ Rotation speed: 1800rpm Similar tests were conducted using the following six types of cage bearings as comparative examples. Was.

(B) 30% WS ₂ -MoS ₂ content of the sintered bronze alloy (b) Ekanoru resin (aromatic polyester) (c) B ₄ C-containing ceramics (d) lead bronze casting (LBC3C) (e) Rulon E ( (Fluorine resin-based) (f) PEEK-based composite material without addition of MoS _{2 The} results obtained by the measurement are shown in FIG. 4 and Table 1.

In FIG. 4, a smaller motor torque during operation is better because bearing loss is smaller. When lubrication deteriorates, the torque increases, and eventually the bearing seizes and its life is extended. L in the figure
Indicates the lifetime point.

The ball bearing using the cage of the present invention has a smaller motor torque and less fluctuation than the comparative example, and has a long life.

The wear amount in Table 1 shows the wear volume per rotation of the cage (× 10 ⁻⁸ mm ³ / rev). From this result, it can be seen that the wear amount of the cage of the present invention is smaller than that of the cage made of another material both in vacuum and in air.

In addition, although the method by injection molding was used in this embodiment,
It can also be formed by extrusion or compression molding.

FIG. 5 shows the results of measuring the dynamic friction coefficient of PEEK and composite materials in a vacuum using a pin-on-disk friction tester. For the PEEK-PTFE-aramid fiber mixture, the fifth
As shown in FIG. 5A, the dynamic friction coefficient in vacuum decreases as the friction distance increases, but the fluctuation is large. When an appropriate amount of MoS ₂ is added, the coefficient of friction is reduced and the fluctuation is small, as shown in FIG. 5 (b). Observation of the friction surface shows that the former has transfer unevenness, while the latter shows stable transfer uniformly over the entire friction surface, and the effect of adding MoS ₂ is obtained.

Instead of disulfide Morubuden MoS _2, using a tungsten disulfide WS _2, or similar results by the addition of both was obtained.

〔The invention's effect〕

As described above, the rolling bearing cage of the present invention has a polytetrafluoroethylene resin content of 10 to 40% by weight, an aramid fiber of 5 to 30% by weight, and one or both of molybdenum disulfide and tungsten disulfide having a content of 5 to 30%. Since the weight% and the balance are composed of a composite material of polyetheretherketone resin, when the bearing rotates, sliding friction occurs between the pocket wall of the cage and the rolling element. It keeps transferring thin films stably each time, keeps good lubricity, and has low friction coefficient and little fluctuation, so low wear and long life can be obtained, and operating loss can be reduced by eliminating uneven lubrication. .

In addition, there is no generation of glass in a vacuum and there is little abrasion of the cage even in the atmosphere, so it can be used in both atmospheres, and since the cage is made of synthetic resin, the friction noise is small and rolling is excellent in machinability Bearings can be provided.

In addition, by arranging the aramid fibers in the axial direction, the wear resistance in the circumferential direction can be increased, and there is an effect that the life can be prolonged and dust generation can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a cylindrical injection molding for manufacturing the cage of the present invention, FIG. 2 is a perspective view of a rolling bearing cage of the present invention, and FIG. 3 is a cage of the present invention. FIG. 4 is a cross-sectional view showing the configuration of the incorporated ball bearing, FIG. 4 is a characteristic diagram showing changes in motor torque and life of the ball bearing, and FIG. 5 is a characteristic diagram showing measurement results of the coefficient of friction. Reference numeral 1 denotes an annular molded product, 2 denotes a runner, 3 denotes an aramid fiber, 5 denotes a cage, 6 denotes a pocket hole, 7 denotes a ball bearing, 8 denotes an inner ring, 9 denotes an outer ring, and 10 denotes a rolling element.

Claims (2)

(57) [Claims] 1. A polytetrafluoroethylene resin of 10 to 40% by weight, an aramid fiber of 5 to 30% by weight, one or both of molybdenum disulfide and tungsten disulfide of 5 to 30% by weight, and a balance of polyether ether ketone resin. A cage for a rolling bearing, comprising a composite material. 2. The roller bearing retainer according to claim 1, wherein said aramid fibers are arranged in an axial direction.