JP2525490B2 - Plastic cage for bearing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a cage for various bearings used under severe conditions. More specifically, the present invention relates to various bearing cages made of a thermoplastic resin composition having excellent heat resistance, oil resistance, chemical resistance, moldability, and the like.

[Conventional technology]

Generally, rolling bearings are classified into ball bearings and bearings depending on the type of rolling elements. To further classify cages of rolling bearings in more detail and to cite typical ones, examples of ball bearings include cages such as general type cages, crown type cages, and thrust ball bearings for angular bearings. On the other hand, as for the roller bearing, for example, a roller bearing retainer such as a tapered roller bearing retainer, a spherical roller bearing retainer, a cylindrical roller bearing retainer, a thrust roller bearing retainer, and a thrust spherical bearing retainer. There is.

As a cage for rolling bearings made of plastic (hereinafter, abbreviated as a cage), a so-called polyamide resin having excellent mechanical properties such as moldability and flexibility and productivity such as raw material cost is used. Nylon cages have been widely used. As an example of the cage, a main part of a crown type cage is shown in FIG. This cage 1 has a claw portion 2 on its upper portion, and a rolling element 4 such as a steel ball is incorporated in a pocket portion 3 having a narrow entrance and exit to rotatably retain the rolling element 4.

However, the cage made of nylon deteriorates under the conditions of continuous use temperature of 100 ° C. or higher, or under the condition that extreme pressure additives are added and it comes into contact with oils and other acidic chemicals. Since the desired properties are lost,
Not very suitable for use under such conditions.

Polyphenylene sulfide resin (hereinafter referred to as PPS resin) is a material that can be used under high temperature conditions and is a relatively inexpensive material that can replace nylon, and it has heat resistance and chemical resistance. It also has excellent moldability. This PPS resin has the following general formula It is a polymer comprising a repeating unit represented by: Such a polymer is obtained, for example, by reacting sodium sulfide and P-dichlorobenzene in an amide solvent such as N-methylpyrrolidone or dimethylacetamide or a sulfone solvent such as sulfolane. The resin is polymerized. There are two types of PPS resins, a crosslinkable PPS resin (also called a branched PPS resin) and a linear PPS resin. The former crosslinkable PPS resin has a low viscosity and a low molecular weight P, for example, a melt viscosity after polymerization of about 20 to 100 poise.
The PS resin is heated to a temperature below its melting point in air to oxidize and crosslink to increase the melt viscosity, or by intentionally adding a crosslinking agent or branching agent to introduce a crosslink or branch structure to increase the melt viscosity. are doing.

However, the crosslinkable PPS resin thus obtained is
The melt viscosity is increased, that is, the heat resistance is improved, but it is considerably brittle and lacks flexibility. Therefore, it is unsuitable as a material for a cage that requires flexibility when the rolling element 4 is assembled in the pocket 3.

On the other hand, the linear PPS resin is a PPS resin in which the molecular chain is linearly grown to a high molecular weight in the polymerization stage, and is characterized by being extremely flexible and tough as compared with the above-mentioned crosslinkable PPS resin. is there. Focusing on this point, a proposal of using a linear PPS resin as a bearing retainer is disclosed in Japanese Patent Laid-Open No. 64-79419. However, the bearing cage made of this linear PPS resin is excellent in assembling at the time of assembly, but it has thermal stability and mechanical characteristics such as creep resistance at high temperature (150 ° C or higher). Inferior Therefore, the cage may be deformed by the centrifugal force and contact with the outer ring to generate abnormal frictional heat. As a result, the lubricant may be deteriorated and the performance of the bearing may be deteriorated.

Polyethersulfone (hereinafter referred to as PES) is a relatively stable material at high temperatures above 150 ° C.
, Polyetherimide (hereinafter referred to as PEI),
Examples include super engineering plastics such as polyamide-imide (hereinafter referred to as PAI) and polyether ether ketone (hereinafter referred to as PEEK). However, none of these is sufficient for use in a bearing cage as described below.

PES has a high glass transition temperature (about 225 ° C),
For example, there is no resistance to polar compounds such as ketones, esters, ethers, etc., and there is a risk of being immersed by the extreme pressure additive contained in the grease.

Since PEI and PEEK are inflexible, there is a problem of rolling element assembling. In addition, the impact from the rolling element may cause chipping of the nail or the like.

PAI tends to swell and foam due to rapid heating due to the high water absorption characteristic of this resin. Further, there is a risk of hydrolysis due to the alkali component in the extreme pressure additive contained in grease or the like.

Further, there is a liquid crystal polymer (hereinafter referred to as LCP) as a resin that can be injection-molded and has a heat resistance of 300 ° C. But,
This LCP is strong in the force in the direction perpendicular to the alignment direction due to the peculiar resin orientation, but is very weak in the force parallel to the alignment direction. In the case of a cage having a complicated shape, there is a sufficient risk of applying a force parallel to the orientation direction, and therefore it is not appropriate to use the LCP for the cage.

Also, as a polyimide material, there is Vespel SP 21 (manufactured by DuPont) having heat resistance of 350 ° C. or higher, but this cannot be injection-molded, so in the case of molding, cutting after compression molding is required.

[Problems to be Solved by the Invention]

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a plastic cage for bearings having all of various characteristics such as heat resistance, oil resistance, chemical resistance, injection moldability, and heat distortion resistance.

[Means for solving the problem]

This invention comprises a polyimide resin composition comprising a polyimide resin, a lubricant and a fibrous reinforcing agent, wherein the polyimide resin has the following general formula: A thermoplastic polyimide resin consisting of repeating units represented by 100 g of the thermoplastic polyimide resin powder 0.5 g
of p-chlorophenol / phenol mixed solvent (mixing weight ratio: 90:10) having a solution viscosity at 35 ° C. of 0.35 to 0.80 dl / g, and in the total amount of the polyimide resin composition. And (i) 5 to 50% by weight of a fluororesin, at least one lubricant selected from graphite and molybdenum disulfide, and (ii) 0 to 50% by weight of glass fiber, carbon fiber, boron fiber, silicon carbide. An additive comprising at least one fibrous reinforcing agent selected from fibers, carbon whiskers, asbestos, metal fibers and rock wool, and the total amount of the additives (i) and (ii) is 5 to 60% by weight. Is a plastic retainer for bearings.

Regarding the thermoplastic polyimide resin in the present invention,
The manufacturing method is not particularly limited. However, normally, It can be obtained by reacting 4,4'-bis (3-aminophenoxy) biphenyl represented by and pyromellitic dianhydride to generate a polyamic acid, and dehydrating and cyclizing the polyamic acid.

The solution viscosity of thermoplastic polyimide resin is 0.35-0.80dl
/ g. The optimum value cannot be unequivocally determined because the degree of physical properties required depends on the use of the cage, but it is preferably 0.45 to 0.55 dl / g.

In addition to the above thermoplastic polyimide resins, additives widely used in ordinary resin compositions may be blended within a range that does not impair the object of the present invention. It is difficult to express the addition rate in parts by weight because the specific gravities are different from each other, but in volume part, 5 to 50 parts by volume, and preferably 15 to 35 parts by volume, relative to 100 parts of the polyimide resin are preferable. Particularly, in the present invention, as an additive, 5 to 50% by weight (preferably 10 to 40% by weight) is used.
Wt%) lubricant (at least one selected from the lubricants listed below) and 0 to 50 wt% (preferably 0 to 40 wt%) fibrous replenisher (selected from the fibrous reinforcing agents listed below). The total amount of additives is 5 to 60% by weight (preferably 10 to 50% by weight). The additives that can be used are listed below.

Lubricant: Fluororesin, graphite, molybdenum disulfide Fibrous reinforcing agent: Glass fiber, carbon fiber, boron fiber, silicon carbide fiber, carbon whiskers, asbestos, metal fiber, rock wool Flame retardant: Antimony trioxide, carbonic acid Magnesium, calcium carbonate, etc. Electric property improver: Clay, mica, etc. Tracking resistance improver: Asbestos, silica, graphite etc. Thermal conductivity improver: Metal powder such as iron, zinc, aluminum, copper etc. Others: Glass beads, glass balls , Calcium carbonate, alumina, talc, diatomaceous earth, hydrated alumina, shirasu balloon, various metal oxides, natural or synthetic compounds that are stable at 500 ° C or higher with various inorganic contents. Use the above thermoplastic polyimide resin composition. The cage of the present invention can be easily molded by a normal injection molding method. Can. Therefore, a complicated molding method such as cutting after compression molding is not required. Further, the type of the cage of the present invention is not particularly limited, and various types of cages such as the general type cage and the crown type cage as exemplified above can be used.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Synthesis Example 1 (Production of Polyimide Resin) 4,4′-bis (3-aminophenoxy) biphenyl was placed in a reaction vessel equipped with a stirrer, reflux cooling and a nitrogen introducing tube.
3.68 kg (10 mol) and N, N-dimethylacetamide 32.9 k
g was added, and 2.125 kg (9.75 mol) of pyromellitic dianhydride was added at room temperature under a nitrogen atmosphere while paying attention to the rise in solution temperature, and the mixture was stirred at room temperature for about 20 hours to obtain a polyamic acid solution.

In this polyamic acid solution at room temperature under nitrogen atmosphere 2.
02 kg (20 mol) triethylamine and 2.55 kg (25 mol) acetic anhydride were added dropwise. This was stirred at room temperature for about 20 hours to obtain a pale yellow slurry. The slurry was filtered, washed with methanol, then filtered, and dried under reduced pressure at 180 ° C. for 8 hours to obtain 5.28 kg (yield about 97%) of polyimide powder.
The solution viscosity of this polyimide powder was 0.50 dl / g. The solution viscosity is a value measured by dissolving 0.5 g of polyimide powder in 100 ml of a solvent (p-chlorophenol: phenol = 90: 10 weight ratio) by heating, and cooling to 35 ° C. after the dissolution.

Examples 1 to 3 The formulations shown in Table 1 were dry mixed with a Henschel mixer. The raw materials shown in Table 1 are listed below. The blending ratios in Table-1 are all shown in parts by weight.

Thermoplastic Polyimide Polyimide resin produced in Synthesis Example 1 (commercially available,
Mitsui Toatsu Chemicals: New-TPI PAI Polyamideimide resin (Amoco, trade name: Torlon
4203) PPS (Cross-linking type) Polyphenylene sulfide resin (Torprene Co., trade name: T-4) PPS (Linear type) (Kureha Chemical Industry Co., Ltd., trade name: KSP- # 214) PTFE L169 Tetrafluoroethylene resin (Asahi Glass Company, product name: Lubricant L169) Graphite Kanebo, product name: Bell Pearl C2000 glass fiber (Nippon Electric Glass, product name: ECSO3T747DE) Carbon fiber (Toho Rayon, product name: HTA-C6X603) Dry type After mixing, extrude at 370 ℃ ~ 400 ℃ using a twin-screw extruder and granulate, the obtained pellets are injection molding machine (cylinder temperature 370 ~ 400 ℃, injection pressure 1000 kg / cm ² , mold temperature
150 to 200 ° C.), the test pieces defined in each test method described later were molded, and the friction and wear characteristics, bending strength, bending elastic modulus, and softening temperature were measured. Table 1 shows the obtained results. In addition, each test method is as follows.

(1) Assembling test at the time of assembly As shown in FIG.
The degree of damage by the rolling element 4 (steel ball) in the portion of the claw portion 2 of the cage 1 and the assembling property of the steel ball are examined, and the determination is made according to the following criteria.

Degree of damage to the claw part of the cage: ○ …… No damage at all △ …… Slight damage × …… Severe damage Assembleability of steel ball: ○ …… Easy to mount during assembly △ …… Slight resistance during assembly Yes × There is considerable resistance when assembled (2) Durability test of cage claws As shown in Fig. 3, a steel ball with a diameter of ball 6 in pocket 3 of cage 1 is 7.16 mm. A rod 7 equipped with a tester 8
The number of times of withdrawal and withdrawal until the claw portion 2 of the retainer 1 was damaged was measured by taking out and withdrawing at a speed of 50 times / min, and the value is shown in Table-1. The higher the number of times of taking in and out, the cage 1
It can be said that the claw portion 2 has a large fatigue strength and a safety factor when the rolling element 4 of the cage 1 is incorporated in the manufacturing process is high.

(3) Deformation rate measurement test of cage Use lubricant (Nippon Oil Co., Ltd .: urea grease, U295)
A bearing 6203 sealed with 0.8 g and sealed with fluororubber was operated for 200 hours under the conditions of a rotational speed of 15000 rpm, a thrust load of 6.8 kgf, and a temperature of 220 ° C with an operating tester to measure the dimensional deformation rate of the cage outer diameter. The results are shown in Table-1. A smaller dimensional deformation rate indicates that the cage is not deformed.

(4) Cage Deterioration Degree Judgment Test Deterioration degree of the lubricant (Urea grease, U295 manufactured by Nippon Oil Co., Ltd.) after 200 hours of continuous operation was judged under exactly the same conditions as in Test (3), and Table 1 was used. Also described in.

○ …… Discoloration, no deterioration △ …… Discoloration, little deterioration × …… Discoloration, considerably deteriorated (5) Thermal deformation temperature Using a mechanical analyzer (TM-30 manufactured by Shimadzu Corporation) It was determined from the penetration start temperature by the TMA penetration method with a temperature rising rate of 5 ° C./min and a pressure of 18.6 kgf / cm ² (based on ASTM D 648).

Comparative Examples 1 to 3 Dry mixing was performed using a Henschel mixer in the proportions shown in Table 1 in the same manner as in Examples except that PAI was used as the base resin instead of the thermoplastic polyimide, and the mixture was supplied to the twin-screw extruder. Melt mixing and granulation were performed under the conditions of a cylinder temperature of 340 to 350 ° C and a screw rotation speed of 50 to 100 rpm. After that, the cylinder temperature is 340-360 ℃, the mold temperature is 160-210 ℃,
The cage 1 of the bearing 6203 as shown in FIG. 1 was injection-molded under the condition of injection pressure of 500 to 1000 kg / cm ² , and the same test as the example was conducted.

Comparative Examples 4 to 5 In the same manner as in Example except that PPS was used as the base resin instead of the thermoplastic polyimide, dry mixing was performed using a Henschel mixer in the proportions shown in Table-1, and the mixture was supplied to the twin-screw extruder. Melt mixing and granulation were performed under the conditions of a cylinder temperature of 270 to 330 ° C. and a screw rotation speed of 50 to 100 rpm. After that, cylinder temperature 280-340 ℃, mold temperature 100-150 ℃,
The cage 1 of the bearing 6203 was injection-molded as shown in FIG. 1 under the condition of injection pressure of 500 to 1000 kg / cm ² , and the same test as in the example was conducted.

Comparative Example 6 Thermosetting Polyimide Resin (manufactured by DuPont, trade name: VES
A bar material of PEL SP 21) was purchased and cut by cutting this to obtain a retainer 1 of a bearing 6203 as shown in FIG. 1, and the same test was performed.

Comparative Examples 7-8 Table 1 based on the thermoplastic polyimide resin of Synthesis Example 1
The same test was carried out by injection molding in the same manner as in Example 1 except that potassium titanate fiber (manufactured by Otsuka Chemical Co., Ltd., trade name TISMO) was blended in the proportion shown in. The results are shown in Table 1.

As is clear from the results shown in Table 1, the cages of Examples 1 to 3 made of thermoplastic polyimide have excellent assemblability at the time of assembly and durability of the claw portion, and are in a bearing operated at high temperature. The deformation rate is low, which may deteriorate the lubricant,
The cage itself does not deteriorate.

In comparison, the cage of Comparative Examples 1 to 3 made of PAI, P
The cages of Comparative Examples 4 and 5 made of PS all had a large deformation rate after the operation test, and the lubricant and the cage themselves were deteriorated.
Further, the cage of Comparative Example 6 produced by cutting was inferior in assembling property and nail durability.

The nails were inferior in durability. Further, the cages of Comparative Examples 7 to 8 containing a large amount of potassium titanate fibers also showed damage to the nails,
It tended to be inferior in terms of ease of installation, durability, deformation and deterioration of the cage itself.

〔The invention's effect〕

As is clear from the above description, the cage of the present invention has flexibility and is easily incorporated into the bearing, and the deformation rate is low even when used at high temperatures, so the bearing is not damaged,
Moreover, it also has heat resistance, chemical resistance, and injection moldability. The field of use of the cage of the present invention is extremely wide,
It is most suitable as a bearing retainer used in a number of fields such as automatic machinery related industries, general equipment related industries, electrical and electronic related industries and many other fields.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating a main part of a rolling bearing cage,
FIG. 2 is a cross-sectional view showing the relationship between the rolling bearing cage and the bearing for investigating the assemblability of steel balls, and FIG. 3 is the plane of a testing machine for explaining the durability test of the claw portion of the rolling bearing cage. It is a figure. 1 ... Roller bearing cage 2 ... Claws, 3 ... Pockets 4 ... Rolling elements, 5 ... Bearing body

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Claims (1)

(57) [Claims] 1. A polyimide resin composition comprising a polyimide resin, a lubricant and a fibrous reinforcing agent, wherein the polyimide resin has the following general formula: A thermoplastic polyimide resin consisting of repeating units represented by 100 g of the thermoplastic polyimide resin powder 0.5 g
of p-chlorophenol / phenol mixed solvent (mixing weight ratio: 90:10) having a solution viscosity at 35 ° C. of 0.35 to 0.80 dl / g, and in the total amount of the polyimide resin composition. And (i) 5 to 50% by weight of a fluororesin, at least one lubricant selected from graphite and molybdenum disulfide, and (ii) 0 to 50% by weight of glass fiber, carbon fiber, boron fiber, silicon carbide. An additive comprising at least one fibrous reinforcing agent selected from fibers, carbon whiskers, asbestos, metal fibers and rock wool, and the total amount of the additives (i) and (ii) is 5 to 60% by weight. A plastic retainer for bearings, characterized in that