JP3076444B2 - Cage for rolling bearing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cage for a rolling bearing requiring heat resistance, chemical resistance and the like.

[0002]

2. Description of the Prior Art Conventionally, cages for rolling bearings used under severe conditions requiring heat resistance, chemical resistance and the like are mainly made of nylon 66, nylon 46 or the like. A polyamide resin is used. However, recently, there has been a demand for a cage that can be used under even more severe conditions, and it is becoming difficult for polyamide resins to sufficiently meet this demand. For example, when a polyamide resin is used for a retainer of a bearing for a main shaft of a distributor (distributor) in an automobile engine or the like,
The resin cannot withstand the NOx gas, the ozone generated by the spark of the distributor, or the high heat of the engine, and the resin deteriorates rapidly.

[0003] Therefore, polyphenylene sulfide (PP) having better heat resistance and chemical resistance than polyamide resin
Attempts have been made to use S) for cages. PPS
Is a linear thermoplastic resin in which a benzene ring and a sulfur atom are alternately bonded as shown in the following general formula. When used as it is (linear PPS), it is used after being crosslinked by heat treatment or the like. (Crosslinked PPS).

[0004]

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[0005] The crosslinked PPS is obtained by heat-treating linear PPS having a relatively small molecular weight of several thousands to 20,000 at a temperature of about 250 ° C. for about 1 to 24 hours, and showing a degree of crosslinking showing a degree of crosslinking. Is about 30 to 40% and apparent molecular weight is 10
It is manufactured by crosslinking to several tens of thousands to several hundreds of thousands. When a cage is manufactured using this cross-linked PPS as a raw material, the cross-linking is further advanced by heating during molding or the like, and the cross-linking rate is increased to about 50 to 60%. become.

However, as described above, the crosslinked PPS having a high crosslinking rate has a problem that it lacks flexibility and toughness, and is brittle and easily broken. The toughness of the crosslinked PPS can be improved by reinforcing it with a fibrous filler such as glass fiber, but a large amount of the fibrous filler must be blended to achieve the required toughness of the cage.

Further, a crosslinked type P reinforced with a fibrous filler
PS has improved toughness but lacks flexibility,
In particular, as shown in FIG. 2, in the case of a cage for a crown-type ball bearing in which the diameter A of the entrance of the pocket is smaller than the maximum diameter B of the pocket by about 10% and is undercut, the molded product is formed of gold. When the mold is removed from the mold, cracks or cracks may occur in the undercut. For this reason, there is also a problem that the conventional crosslinked PPS cannot form a complicated shape such as a cage having an undercut.

On the other hand, since linear PPS is more flexible than crosslinked PPS, a cage having an undercut can be formed. In order to maintain heat resistance and chemical resistance, a cage using a linear PPS having a relatively high molecular weight (molecular weight of about 80,000 to several hundred thousand) has been proposed (for example, Japanese Patent Application Laid-Open No. Sho 64-79419). JP, JP-A 1-1
No. 20423).

However, even if the linear PPS has a high molecular weight as described above, heat resistance and chemical resistance are inferior to cross-linked PPS, so that high heat resistance and high chemical resistance required for the cage are required. There is a problem that can not achieve the nature. As described above, in the conventional technology, molding is difficult when using a cross-linked PPS, and high heat resistance and high chemical resistance cannot be achieved when a linear PPS is used. At present, rolling bearing retainers that can be used under various conditions have not yet been put to practical use.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a roller bearing retainer that uses PPS as a resin and can be used under more severe conditions. .

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a rolling bearing cage according to the present invention has a molecular weight of 7%.
It is composed of a molding material containing partially crosslinked PPS obtained by partially crosslinking 10,000 to 600,000 linear PPS, and the crosslink rate of the partially crosslinked PPS after molding, which indicates the degree of crosslinking, is 25 to 45.
%.

[0012] The cage for a rolling bearing of the present invention having the above-mentioned structure contains a partially crosslinked PPS having a relatively low crosslinking ratio as a resin component, mainly composed of a linear PPS having a relatively large molecular weight. Has the same flexibility as a cage made of linear PPS. Therefore, according to the present invention, it is possible to manufacture a cage having a complicated shape having an undercut, which cannot be formed by a conventional cross-linked PPS.

Since the partially crosslinked PPS has a partially crosslinked structure as the name implies, the cage for a rolling bearing of the present invention has high heat resistance, which cannot be obtained by the conventional linear PPS. It has high chemical resistance and can be used under more severe conditions. In the cage for a rolling bearing according to the present invention, the cross-linking rate of the partially cross-linked PPS after molding is limited to 25 to 45% as described above. If the cross-linking ratio after molding is less than 25%, it becomes close to that of conventional linear PPS, and high heat resistance and high chemical resistance cannot be achieved. Conversely, when the cross-linking ratio after molding exceeds 45%, the cross-linking type becomes close to the conventional cross-linking type PPS, and the flexibility becomes insufficient, so that a cage having a complicated shape with undercut cannot be obtained.

Linear PP as a raw material of partially crosslinked PPS
The molecular weight of S is limited to 70,000 to 600,000. Linear PPS
If the molecular weight is less than 70,000, a crosslinked product having a moldable viscosity is inevitably increased in crosslinking rate, lacks flexibility and toughness, and becomes brittle and fragile. A similar problem arises. Conversely, if the molecular weight of the linear PPS exceeds 600,000, a sufficient cross-linking rate cannot be obtained if the cross-linked product is to be kept in a moldable viscosity range.
The same problems as the conventional linear PPS occur, such as insufficient heat resistance and chemical resistance.

The partially crosslinked PPS is a conventional crosslinked PPS.
Similarly to the above, it is produced by crosslinking linear PPS by heat treatment or the like. The partially crosslinked PPS produced in this manner can be further crosslinked by heating at the time of producing a molding material such as pellets by blending various additives or at the time of molding a cage using the molding material. Is increased, so that the cross-linking ratio after molding falls within the range of 25 to 45%,
It is necessary to set the crosslinking ratio before molding in a lower range.

The crosslinking ratio of the partially crosslinked PPS before molding is not particularly limited in the present invention, but is preferably 5 to 25%. If the cross-linking ratio before molding is less than 5%, the cross-linking ratio after molding falls below the above range, and the obtained cage for rolling bearings has insufficient heat resistance and chemical resistance.
The same problem may occur. Conversely, if the cross-linking ratio before molding exceeds 25%, the cross-linking ratio after molding exceeds the above range, and the obtained rolling bearing cage lacks flexibility, toughness, and becomes brittle and fragile. Crosslinked PPS
The same problem may occur.

In order to adjust the cross-linking ratio of the partially cross-linked PPS before molding within the above range, the heat treatment time for heat-treating the linear PPS to partially cross-link the PPS or lowering the processing temperature may be used. However, since the crosslinking of the linear PPS is promoted by oxygen, the crosslinking rate of the partially crosslinked PPS can be adjusted even if the oxygen content in the heat treatment atmosphere is reduced. In actual production, the above three methods may be appropriately combined to adjust the cross-linking ratio of the partially cross-linked PPS before molding.

The cage for a rolling bearing according to the present invention may contain a fibrous filler and various additives in addition to the above partially crosslinked PPS. The content ratio of the fibrous filler is not particularly limited, but is preferably 50% by weight or less based on all components. When the content of the fibrous filler exceeds 50% by weight,
The fluidity at the time of heating and melting may be reduced to deteriorate the moldability, and the reinforcing effect of the fibrous filler may be saturated.

Examples of the fibrous filler include glass fiber, carbon fiber, fibrous wollastonite (wollastonite), silicon carbide fiber, boron fiber, alumina fiber, Si-Ti-CO fiber, and metal fiber (copper). , Steel, stainless steel, etc.), aromatic polyamide (aramid) fiber, potassium titanate whisker, graphite whisker, silicon carbide whisker,
Examples include silicon nitride whiskers and alumina whiskers.

In the present invention, a part of the fibrous filler can be replaced with a conventionally known filler. As the filler, powder of heat-resistant resin such as phenol resin, silicone resin, fluorine resin, polyamide imide resin, polyimide resin, aromatic polyamide resin, graphite, alumina, silica, silicon carbide, silicon nitride, carbon black, disulfide Examples include molybdenum, talc, diatomaceous earth, asbestos, magnesium carbonate, calcium carbonate, glass beads, and inorganic powders such as silica balloons.

The cage of the present invention is prepared by melting and kneading the above-described components into a shape usable as a molding material, such as a pellet or a powder, and then using an injection molding machine or the like as in the prior art. It is manufactured by molding. The configuration of the present invention can be applied to all types of cages for various rolling bearings such as ball bearings, needle roller bearings, cylindrical roller bearings, tapered roller bearings, and in particular, those having a shape having an undercut. It can be suitably applied to a retainer.

[0022]

The present invention will be described below based on examples and comparative examples. Formulation Example 1 A partially cross-linked PPS (trade name: SASTIL, product number: GS-30, manufactured by Tosoh Corporation) obtained by partially cross-linking a linear PPS having an average molecular weight of 500,000, and glass fibers, and a glass fiber content of 30 The resin composition was prepared by melt-kneading so as to have a weight%.

Formulation Example 2 A resin composition was prepared in the same manner as in Formulation Example 1 except that the glass fiber content was changed to 40% by weight. Formulation Example 3 Crosslinked PPS obtained by crosslinking linear PPS having an average molecular weight of 10,000
(Product name SUSTIL, product number GS-40 manufactured by Tosoh Corporation)
And use a glass fiber content of 40% by weight.
A resin composition was prepared in the same manner as in Formulation Example 1 except that the above.

Formulation Example 4 Resin was prepared in the same manner as in Formulation Example 1 except that linear PPS having an average molecular weight of 700,000 (manufactured by Polyplastics Co., Ltd.) was used and the glass fiber content was 40% by weight. A composition was made. For the resin composition of each of the above formulation examples,
The following tests were performed.

Tensile test ASTM D 638-82a "Standard Test Method
For each of the above resin compositions, the tensile strength at break (kgf / cm ² ) and the tensile elongation at break (%) were measured according to “for TENSILE PROPERTIES OF PLASTICS”. A Type I test piece prepared from each resin composition was used for the measurement.

Bend test ASTM D 790-81 "Standard Test Method f
or FLEXURAL PROPERTIES OF UNREINFORCED AND REINFOR
CED PLASTICS AND ELECTRICAL INSULATING MATERIALS
(Test Method for Bending Properties of Reinforced or Unreinforced Plastic and Electrical Insulator) ", the bending strength (kgf / cm ² ) of each of the above resin compositions was measured. For the measurement, a test piece having a length of 5 inches, a width of 1/2 inches and a height of 1/4 inch, which was produced from each resin composition, was used.

Also, the above-mentioned ASTM D 790 of 11.
The flexural modulus (kgf / cm ² ) was calculated by the equation described in section 11. Izod impact test ASTM D 256-81 "Standard Test Method f
or IMPACT RESISTANCEOF PLASTICS AND ELECTRICAL INS
The Izod impact strength (kgf · cm / cm) of each of the above resin compositions was measured in accordance with ULATING MATERIALS (test method for impact resistance of plastics and electrical insulators). For the measurement, a test piece having a notch of 1/8 inch produced from each resin composition was used.

Heat Deformation Temperature Measurement ASTM D 648-82 "Standard Test Method f
or DEFLECTION TEMPERATURE OF PLASTICS UNDER FLEXUR
AL LOAD (Plastic load deflection temperature test method) "
The heat deformation temperature (° C.) of each resin composition was measured by applying a stress of 18.6 kgf / cm ² to the test piece in accordance with the following. For the measurement, a length of 5 inches prepared from each resin composition
A test piece having a width of 1/4 inch and a height of 1/2 inch was used.

Table 1 shows the above results.

[0030]

[Table 1]

From the results shown in Table 1 above, the resin compositions of Formulation Examples 1 and 2 containing the partially crosslinked PPS as a resin component, which are the raw materials of the cage of the present invention, are all the conventional crosslinked PP.
Compared with the resin composition of Formulation Example 3 containing S as a resin component and the resin composition of Formulation Example 4 containing a conventional linear PPS as a resin component, the resin composition has higher tensile elongation at break and higher flexural strength. When the resin compositions of Formulation Examples 2, 3, and 4 having the same glass fiber content are compared, the resin composition of Formulation Example 2 has a large tensile strength at break. Regarding the flexural modulus and Izod impact strength, the resin compositions of Formulation Examples 1 and 2 show values equal to or higher than those of Formulation Examples 3 and 4,
From this, the partially crosslinked PPS is different from the conventional crosslinked PPS.
It was found that S had the excellent points of S and linear PPS.

Examples 1 and 2, Comparative Examples 1 and 2 The resin compositions of the above Formulation Examples 1 to 4 were pelletized, and the pellets of each of the Formulation Examples were molded using an injection molding machine.
A pocket-shaped ball bearing retainer having a pocket shape shown in FIG. 2 having a diameter of 0.1 mm, an inner diameter of 15.5 mm, a number of pockets of 7, and a pitch circle diameter (PcD) of 17.65 mm was formed.

The following tests were carried out on the cages for crown type ball bearings of the above Examples and Comparative Examples. Evaluation of Formability The cages for crown-type ball bearings manufactured in the above Examples and Comparative Examples were observed for the occurrence of cracks or cracks in the undercut portion. If no cracks or cracks occurred, ○ (good moldability), and if it occurred, × (poor moldability)
Was evaluated.

Cage strength measurement (initial value) Cage H in which no cracks or cracks were observed was placed in FIG.
(a) As shown in (b), the projections 11 and 12 of the pair of jigs 1 and 2
1 and the jigs 1 and 2 were measured for breaking strength (kgf) when pulled up and down as indicated by arrows in the figure. Cage strength measurement (after heat resistance) After the cage was heated at 150 ° C. for 1000 hours with grease applied to the surface of the cage where no cracks or cracks were observed, the breaking strength (kgf) was determined in the same manner as above. Measured.

Cage strength measurement (after chemical resistance) After the cage in which no cracks or cracks were observed was immersed in a 10% nitric acid solution at room temperature for 1000 hours, the breaking strength (kgf) was measured in the same manner as described above. It was measured. The above results are shown in Table 2 together with the cross-linking ratio of PPS after molding in the cage for crown type ball bearings of each of the examples and comparative examples.

[0036]

[Table 2]

From the results in Table 2 above, it can be seen that the conventional crosslinked PPS
Of the crown ball bearing of Comparative Example 1, which is molded from the resin composition of Formulation Example 3 containing as a resin component, the cross-linking ratio after molding is significantly larger than 45%. Cracks were generated, which proved to be inflexible. In addition, conventional linear P
The crown ball bearing retainer of Comparative Example 2 molded from the resin composition of Formulation Example 4 containing PS as a resin component and having a cross-linking ratio after molding of significantly less than 25% was obtained after heat resistance and chemical resistance. The strength was remarkably reduced, which indicates that the heat resistance and the chemical resistance were poor. Comparative Example 2 above
No cracks or cracks were observed during molding of the cage for crown type ball bearings, but burrs occurred.

On the other hand, each of the cages for crown ball bearings of Examples 1 and 2 molded from the resin compositions of Formulation Examples 1 and 2 containing the partially crosslinked PPS as a resin component cracked during molding. No cracks or cracks were observed, indicating excellent flexibility, and little deterioration in strength after heat resistance and chemical resistance, indicating excellent heat resistance and chemical resistance. Moreover, since no burr was generated when the cage for the crown type ball bearings of Examples 1 and 2 was formed, it was also found that the partially crosslinked PPS was excellent in overall formability.

[0039]

As described above, according to the present invention, a partially crosslinked PPS obtained by partially crosslinking a linear PPS having a relatively high molecular weight is used as a resin component, so that a conventional crosslinked PPS can be molded. It is possible to mold a cage that has a complicated shape that was impossible and requires high dimensional accuracy, especially a cage with an undercut, and the molded cage uses linear PPS. It has excellent heat resistance and chemical resistance as compared to those that have been used. Therefore, according to the present invention, it is possible to put into practice a rolling bearing cage that has been impossible to realize conventionally and that can be used under more severe conditions.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are diagrams for explaining a method of measuring the strength of a cage for a crown type ball bearing manufactured in an example and a comparative example.

FIG. 2 is an enlarged side view of a pocket of a cage for a crown type ball bearing.

Continuation of front page (56) References JP-A-3-96716 (JP, A) JP-A-4-29617 (JP, A) JP-A-3-117722 (JP, A) JP-A-1-120423 (JP) , A) JP-A-64-79419 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16C 33/44 F16C 33/56

Claims (3)

(57) [Claims] 1. A molding material containing a partially crosslinked polyphenylene sulfide obtained by partially crosslinking a linear polyphenylene sulfide having a molecular weight of 70,000 to 600,000. A retainer for a rolling bearing, wherein the cross-linking ratio shown is 25 to 45%. 2. The rolling bearing cage according to claim 1, further comprising a fibrous filler. 3. The rolling bearing cage according to claim 1, wherein the cross-linking ratio of the partially cross-linked polyphenylene sulfide before molding is 5 to 25%.