WO2017022794A1 - Holder for rolling bearing and rolling bearing - Google Patents

Abstract

Provided are a rolling bearing and a holder, the rolling bearing having a sliding surface with excellent slidability even under conditions of high slip velocity and high surface pressure lubricating oil. The holder holds the rolling element of the rolling bearing used in a lubricating oil environment, and the holder has a base material and a sliding layer formed on the surface of the base material. The sliding layer is a fluororesin layer in which either: (1) the fluororesin has a three-dimensional structure in the sliding layer surface where the fluororesin layer does not make contact with the base material and in layers proximal thereto, the fluororesin has a two-dimensional structure in the surface where the fluororesin layer makes contact with the base material and in layers proximal thereto, and the content ratio of the three-dimensional structure of the fluororesin continuously decreases from the sliding layer surface toward the surface in contact with the base material; or (2) the three-dimensional structure of the fluororesin is continuous from the sliding layer surface toward the surface in contact with the base material.

Description

Roller bearing cage and rolling bearing

TECHNICAL FIELD The present invention relates to a rolling bearing cage and a rolling bearing, and in particular, has excellent wear resistance and seizure resistance on the cage surface, and can maintain the excellent wear resistance and seizure resistance for a long period of time, The present invention relates to a rolling bearing using the cage.

¡Sliding surfaces such as rolling bearings and cages are supplied with lubricating oil or lubricating grease to reduce rolling friction or sliding friction. Further, a surface treatment for improving the slidability is applied to the sliding surface. One of the surface treatments is a method of forming a fluorine resin film. For example, a method of improving wear resistance and adhesion to a substrate by irradiating a polytetrafluoroethylene (hereinafter referred to as PTFE) coating formed on a sliding portion of a sliding member with a dose of 50 to 250 kGy. Is known (Patent Document 1).

A fluororesin film is formed on the surface of a base material excellent in heat resistance selected from metal materials such as polyimide resin, copper, aluminum and alloys thereof, ceramics, and glass, and at a temperature equal to or higher than the melting point of the fluororesin. A method for producing a modified fluororesin coating material that emits ionizing radiation is known (Patent Document 2).

As a sliding member made of fluororesin used for non-lubricated bearings, dynamic seals, etc., the fluororesin is heated above its crystalline melting point, and ionizing radiation is emitted within the range of irradiation dose of 1 kGy to 10 MGy in the absence of oxygen. Irradiated fluororesins are known (Patent Document 3).

A film or sheet-like product in which a film or sheet-like gradient material composed of PTFE and a substrate selected from the group consisting of aluminum, iron, stainless steel, polyimide and ceramics are laminated, One surface that is not in contact with the base material and the polymer existing in the neighboring layer have a three-dimensional structure, and the other surface that is in contact with the base material of the material and the polymer existing in the neighboring layer have a two-dimensional structure. A film or sheet-like product in which the content of the three-dimensional structure of the polymer existing between the one surface and the other surface varies continuously, and the thickness of the material is 5 to 500 μm Is known (Patent Document 4).

On the other hand, there are rolling bearings used for engines such as automobiles and motorcycles, in particular needle roller bearings with a cage, and the cage surface is silver-plated to prevent seizure of the cage surface. This needle roller bearing with a cage is composed of a pressed metal cage that holds the needle rollers at regular intervals, and the entire surface of the cage is silver-plated (Patent Document 5).

JP 2010-155443 A JP 2002-225204 A JP-A-9-278907 Japanese Patent No. 5454903 Japanese Patent No. 5189427

However, the manufacturing method shown in Patent Document 1 is a method for improving adhesion to a base material because it is used under non-lubricated and low surface pressure conditions. Lubricating oil required for sliding surfaces of various machines It is difficult to apply in the case of medium, high slip speed and high surface pressure.
The fluororesin coating described in Patent Document 2 is intended to simultaneously cause a cross-linking reaction of a fluororesin and a chemical reaction between the fluororesin and a substrate surface, thereby achieving strong adhesion between the two. In the case of an iron substrate such as a cage or a cage, it is difficult to generate a chemical reaction with the surface of the substrate, and there is a problem that strong adhesion cannot be achieved.
The sliding member described in Patent Document 3 is used for a non-lubricated bearing, a dynamic seal, and the like, and relates to a sliding member made of a fluororesin rather than a film shape. Therefore, the characteristics as a coating material are unknown, and it is difficult to apply to rolling bearing applications that require high slip speed and high surface pressure in lubricating oil.
Similar to the coating produced by the method described in Patent Literature 1, the coating described in Patent Literature 4 is evaluated with a flat plate test piece, a low surface pressure, a low sliding speed, and no lubrication. It is not known whether it can be used under pressure, high slip speed and oil lubrication.
In the cage that has been subjected to silver plating described in Patent Document 5, a cage that requires less change with time in the amount of wear on the sliding surface is required, and a sliding material that replaces silver plating is required. . Further, silver plating has a problem that it is sulfided by a sulfur component contained in engine oil. When the silver plating applied to the surface of the cage is sulfided, peeling or dropping occurs from the cage, and the base material of the cage is exposed.

The present invention has been made to cope with such a problem, and is a rolling bearing holding having a sliding surface excellent in slidability even under conditions of high sliding speed and high surface pressure in lubricating oil. It is an object of the present invention to provide a rolling bearing using the cage and the cage.

The rolling bearing cage of the present invention holds a rolling element of a rolling bearing used in an oil lubricated environment, and has a base material and a sliding layer formed on the surface of the base material. This sliding layer is a fluororesin layer, and the fluororesin present on the surface of the sliding layer that is not in contact with the base material of the fluororesin layer and its neighboring layers has at least a three-dimensional structure. That the surface of the sliding layer and its neighboring layers have at least a three-dimensional structure is not limited to the fact that the entire portion of the sliding layer is made of only a three-dimensional fluoropolymer, and does not impair the characteristics of the three-dimensional structure. Of these, a part of the fluororesin having a two-dimensional structure may be included in this part. Similarly, the fact that the surface on the substrate side and the vicinity thereof have an uncrosslinked two-dimensional structure is not limited to the fact that this entire portion of the sliding layer is made of only a two-dimensional structure fluororesin, As long as the characteristics are not impaired, a part of the fluororesin having a three-dimensional structure may be included in this part. In the present invention, the vicinity means a layer less than 2.5 μm from the target surface.

In the first aspect of the sliding layer, the surface of the sliding layer that is not in contact with the base material and the fluororesin existing in the neighboring layer have a three-dimensional structure, and the surface in contact with the base material and the vicinity thereof. The fluororesin present in the layer has a two-dimensional structure. In particular, the content of the three-dimensional structure of the fluororesin continuously decreases from the surface of the fluororesin layer toward the surface in contact with the base material. In the second aspect of the sliding layer, the three-dimensional structure of the fluororesin present on the surface of the sliding layer that is not in contact with the base material and in the vicinity thereof is continuous toward the surface in contact with the base material. ing.

The fluororesin is a PTFE resin, and the thickness of the sliding layer is 5 μm or more and less than 40 μm.
The base material is an iron-based metal material.

The rolling bearing of the present invention is a rolling bearing using the cage of the present invention.

In the rolling bearing retainer of the present invention, the fluororesin present on the surface of the sliding layer that is not in contact with the base material and its neighboring layers has at least a three-dimensional structure. Therefore, the lubricating oil has a high sliding speed and a high surface pressure. Wear can be suppressed even under conditions, and the life of the bearing can be maintained for a long time. Moreover, the rolling bearing using this cage is excellent in slidability in lubricating oil.

It is sectional drawing of the sliding layer from which a cross section becomes a gradient material. It is sectional drawing of the sliding layer from which a cross section becomes a uniform material. It is an enlarged view of the NMR chart of Experimental example A1. It is an enlarged view of the NMR chart of Experimental example A2. It is an enlarged view of the NMR chart of Experimental example A3. The normalized signal intensity ratio of -82 ppm associated with crosslinking. It is a perspective view of the cage for rolling bearings which uses a needle roller as a rolling element. It is a perspective view which shows a needle roller bearing. It is a longitudinal cross-sectional view of a 4-cycle engine. It is a figure which shows the outline | summary of an abrasion amount test apparatus.

The rolling bearing cage of the present invention has a sliding layer formed on a substrate. An example of a sectional view of the sliding layer is shown in FIG. FIG. 1 shows an example in which the cross section is a gradient material. The sliding layer 21 is composed of a cross-linked fluororesin layer formed on the surface of the metal substrate 22. The cross-linked fluororesin layer has a cross-linked structure in which the fluororesin layer has a three-dimensional structure in which the surface 23 of the fluororesin layer that is not in contact with the metal substrate and the fluororesin present in the vicinity thereof. Further, the surface 24 of the fluororesin layer in contact with the metal substrate 22 and the fluororesin present in the vicinity thereof have an uncrosslinked structure having a two-dimensional structure. The content of the three-dimensional structure of the fluororesin existing between the surface 23 and the surface 24 in contact with the substrate is continuous from the surface 23 of the fluororesin layer toward the surface 24 in contact with the substrate. It has become less.

FIG. 2 shows a cross-sectional view of another sliding layer formed on the substrate. FIG. 2 shows an example in which the cross section of the sliding layer is a uniform material. The sliding layer 21 consists of a crosslinked fluororesin layer formed on the surface 22 of the iron-based metal substrate. The sliding layer 21 made of a crosslinked fluororesin has a crosslinked structure consisting of a three-dimensional structure from the surface 24 in contact with the metal substrate to the surface 23 of the sliding layer.

Examples of the base material that can be used for the rolling bearing cage of the present invention include an aluminum material, an iron-based metal material, a polyimide material, or a ceramic material. Among these, a ferrous metal material is preferable as the rolling bearing cage.
Examples of the iron-based metal material include bearing steel used for rolling bearings, carburized steel, carbon steel for machine structure, cold rolled steel, hot rolled steel, and the like. The ferrous metal material is adjusted to a predetermined surface hardness by quenching and tempering after processing into the shape of the cage. For example, in the case of a ferrous metal material cage using chromium molybdenum steel (SCM415), it is preferable to use an ferrous metal material whose Hv value is adjusted to 484 to 595.

The sliding layer is made of a fluororesin layer formed on the surface of the iron-based metal material.
Examples of fluororesins include PTFE, tetrafluoroethylene-perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as PFA), tetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referred to as FEP), ethylene-tetrafluoroethylene copolymer. Examples include polymers, polyvinylidene fluoride, and polyvinyl fluoride. These resins can be used alone or as a mixture. Of these, PTFE which is excellent in heat resistance and slidability is preferable.

The fluororesin layer before cross-linking can be produced by applying and drying, followed by baking using an aqueous dispersion in which PTFE resin particles are dispersed. Examples of the aqueous dispersion in which PTFE resin particles are dispersed include, for example, Polyflon = PTFE enamel manufactured by Daikin Industries, Ltd. The aqueous dispersion may contain a nonionic surfactant such as polyoxyethylene alkyl ether, an inorganic pigment such as carbon black, and water as a main solvent. Moreover, an antifoamer, a desiccant, a thickener, a leveling agent, a repellency inhibitor, etc. can be mix | blended.
The cross-linked fluororesin layer is a cross-linked fluororesin layer in which at least the surface and the vicinity thereof are cross-linked.

A method for forming the sliding layer on the surface of the iron-based metal material will be described below.
(1) Surface treatment of iron-based metal materials For iron-based metal materials, the roughness (Ra) of the metal material surface is adjusted in advance to 1.0 to 2.0 μm using shot blasting before forming the sliding layer. Thereafter, it is preferably immersed in an organic solvent such as petroleum benzine and subjected to ultrasonic degreasing for about 5 minutes to 1 hour.

(2) Application of aqueous coating solution for forming the fluororesin layer Before the aqueous coating solution for forming the fluororesin layer, in order to improve the dispersibility of the aqueous dispersion, it is rotated for 1 hour at, for example, 40 rpm using a ball mill. Redistribute. The re-dispersed aqueous coating solution is filtered using a 100 mesh wire net and painted using a spray method.
(3) Drying of aqueous coating solution for forming the fluororesin layer The aqueous coating solution is applied and then dried. As drying conditions, for example, drying in a thermostat at 90 ° C. for about 30 minutes is preferable. The layer thickness of the fluororesin layer after drying is 5 μm or more and less than 40 μm, preferably 15 to 30 μm. If the thickness is less than 5 μm, the metal substrate may be exposed due to peeling or initial wear due to poor adhesion of the coating. If it is 40 μm or more, cracks during film formation or peeling during operation may deteriorate the lubrication state.
As a method for coating the fluororesin layer, any coating method can be used as long as it can form a film such as a dipping method and a brush coating method in addition to the spray method. The spray method is preferable in view of making the surface roughness and coating shape of the coating as small as possible and considering the uniformity of the layer thickness.

(4) Firing After drying the fluororesin layer, in the heating furnace, in air, at a temperature higher than the melting point of the fluororesin, preferably (melting point (Tm) + 30 ° C.) to (melting point (Tm) + 100 ° C.), 5 to 40 minutes Firing within the range of. When the fluororesin is PTFE, it is preferably fired in a heating furnace at 380 ° C. for 30 minutes.

(5) Crosslinking of fluororesin layer From the temperature lower than the melting point of the fluororesin layer to an irradiation temperature of 30 ° C lower than the melting point of the fluororesin layer, preferably 50 ° C lower than the melting point, preferably 10 ° C lower than the melting point of the fluororesin layer. The fluororesin layer is cross-linked by irradiating with radiation at a temperature not higher than 20 ° C. above the melting point and with an irradiation dose of more than 250 kGy and 750 kGy or less. Examples of radiation include α rays (particle beams of helium-4 nuclei emitted from radionuclides that undergo α decay), β rays (negative electrons and positrons emitted from nuclei), and electron beams (almost constant kinetic energy). Particle beam such as electron beam, generally generated by accelerating thermionic electrons in vacuum; gamma ray (emitted and absorbed by transitions between energy levels of nuclei and elementary particles, pair annihilation of elementary particles, pair production, etc.) Ionizing radiation such as an electromagnetic wave having a short wavelength). Among these radiations, from the viewpoint of crosslinking efficiency and operability, electron beams and γ rays are preferable, and electron beams are more preferable. In particular, an electron beam has advantages such as easy availability of an electron beam irradiation apparatus, simple irradiation operation, and the ability to employ a continuous irradiation process.

The cross-linking of the fluororesin layer does not proceed sufficiently except in the temperature range where the irradiation temperature is 30 ° C. lower than the melting point of the fluororesin layer to 50 ° C. higher than the melting point. In addition, in order to efficiently perform crosslinking in the irradiation atmosphere, it is necessary to lower the oxygen concentration in the irradiation region by evacuation or inert gas injection. The range of oxygen concentration is preferably 0 to 300 ppm. In order to maintain the oxygen concentration in the above concentration range, an inert atmosphere by nitrogen gas injection is preferable from the viewpoint of operability and cost.
When the irradiation dose is 250 kGy or less, crosslinking is insufficient, the wear amount is large, and the metal substrate may be exposed. In addition, when the irradiation dose exceeds 750 kGy, crosslinking proceeds more than necessary, and the hardness of the coating increases, so that the coating becomes brittle and damage to the coating such as peeling may easily occur.

In the case of a gradient material in which the content of the three-dimensional structure of the fluororesin continuously decreases from the surface of the sliding layer to the surface in contact with the base material, the acceleration voltage upon irradiation is 40 kV or more and 500 kV Less than, preferably 50 to 100 kV. If it is less than 40 kV, the penetration of the electron beam into the vicinity of the surface layer of the fluororesin layer becomes shallow, and if it is 500 kV or more, the entire fluororesin layer is cross-linked. When radiation is applied to the fluororesin layer, the intensity of the radiation attenuates inside the polymer, so that the radiation can reach the irradiated surface sufficiently, but the other surface cannot be tilted. Form material.

When the fluororesin is a uniform material in which the three-dimensional structure of the fluororesin is continuous from the surface of the sliding layer toward the surface in contact with the base material, the acceleration voltage when irradiated is preferably 500 kV or more, preferably 800 to 1200 kV. When the fluororesin layer is irradiated with radiation at this acceleration voltage, the radiation reaches all layer surfaces from the irradiated surface to the substrate surface, and a crosslinked fluororesin layer crosslinked from the surface to the substrate surface is obtained.

The layer thickness of the sliding layer obtained by the method described above is 5 μm or more and less than 40 μm, preferably 15 μm or more and less than 30 μm. If the layer thickness is less than 5 μm, the metal substrate may be exposed due to peeling due to poor adhesion of the coating or due to initial wear. If it is 40 μm or more, cracks during film formation or peeling during operation may deteriorate the lubrication state. By setting the layer thickness in the range of 5 μm or more and less than 40 μm, it is possible to prevent the metal substrate from being exposed due to initial wear and to prevent peeling during operation over a long period of time.

Next, it will be described that the fluororesin layer used in the present invention has a crosslinked structure. In general, a fluorine-based resin, particularly a PTFE resin, is chemically very stable and extremely stable against an organic solvent, so that it is difficult to identify the molecular structure or molecular weight. Furthermore, since the PTFE resin forms a three-dimensional structure by cross-linking, it becomes more difficult to dissolve in a solvent, and structural analysis becomes more difficult. However, the measurement and analysis by ¹⁹ F Magical Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) Method (High Speed Magnetic Nuclear Resonance) makes it possible to identify the three-dimensional structure of PTFE resin.

In order to confirm the formation of a three-dimensional structure by crosslinking, the following Experiment A and Experiment B were performed. The experiment A is for confirming the formation of the gradient material, and the experiment B is for confirming the formation of the uniform material.
[Experiment A]
(1) Preparation of test piece Test piece: A PTFE resin layer was formed on a metal flat plate of 30 mm × 30 mm and 2 mm thickness made of SPCC. As the PTFE resin layer, a top coating (model number: EK-3700C21R) manufactured by Daikin was used. The drying time was 30 minutes in a constant temperature bath at 90 ° C., followed by baking in a heating furnace at 380 ° C. for 30 minutes.
Thereafter, the specimen was irradiated with an electron beam from the surface of the PTFE resin layer under the following conditions.
Equipment used: EB engine manufactured by Hamamatsu Photonics Co., Ltd. Acceleration voltage: 70 kV
Irradiation dose: Experimental example A1 is 0 kGy (unirradiated), Experimental example A2 is 500 kGy, Experimental example A3 is 1000 kGy
Film temperature during irradiation: 340 ° C
Chamber atmosphere during irradiation: Nitrogen

(2) Test piece coating test example A1: PTFE coating (irradiation dose: 0 kGy, layer thickness: 20 μm)
Experimental Example A2: PTFE coating (irradiation dose: 500 kGy, layer thickness: 20 μm)
Experimental Example A3: PTFE coating (irradiation dose: 1000 kGy, layer thickness: 20 μm)

(3) NMR measurement The measurement was performed using an NMR device JNM-ECX400 manufactured by JEOL Ltd., using a suitable measurement nuclide ( ¹⁹ F), resonance frequency (376.2 MHz), MAS (Magic Angle Spinning) rotation speed (15 and 12 kHz), sample amount (about 70 μL in a 4 mm solid state NMR tube), waiting time (10 seconds) and measurement temperature (about 24 ° C.).

(4) Results The results are shown in FIGS. 3 shows NMR of Experimental Example A1, FIG. 4 shows NMR of Experimental Example A2, and FIG. 5 shows an enlarged view of the NMR chart of Experimental Example A3. 3 to 5, the upper row represents the MAS rotational speed 15 kHz, and the lower row represents the MAS rotational speed 12 kHz. FIG. 6 is a graph obtained by normalizing the signal intensity at −82 ppm, the intensity of which increases with crosslinking, with the signal intensity at −122 ppm as the main signal. In FIG. 6, the upper part represents the measured value, and the lower part represents the graph. It is considered that the higher the signal intensity ratio is, the more the degree of crosslinking proceeds.

When a PTFE resin layer not subjected to radiation irradiation (Experimental Example A1, 0 kGy) was measured under the above conditions, signals of -82 ppm, -122 ppm, and -162 ppm, which are chemical shift values (δ ppm), were obtained at a MAS rotational speed of 15 kHz. Observed (the upper part of FIG. 3). Similarly, signals of −58 ppm, −82 ppm, −90 ppm, −122 ppm, −154 ppm, and −186 ppm were observed at the MAS rotational speed of 12 kHz (lower part of FIG. 3). It is known that −122 ppm is the signal of the F atom in the —CF ₂ —CF ₂ — bond, and −82 ppm is the signal of the F atom of —CF ₃ in the —CF ₂ —CF ₃ bond. Therefore, the signals of −82 ppm and −162 ppm at a MAS rotational speed of 15 kHz, and −58 ppm, −90 ppm, −154 ppm and −186 ppm at a MAS rotational speed of 12 kHz are spinning side bands (SSB). A broad signal is observed in the range of −122 ppm to −130 ppm hidden by the −122 ppm signal. This signal is the signal of the F atom of —CF ₂ — in the —CF ₂ —CF ₃ bond that should be observed at −126 ppm. Therefore, the uncrosslinked PTFE resin layer not irradiated with radiation is an NMR chart having signals of −122 ppm attributed to —CF ₂ —CF ₂ — bonds, −82 ppm and −126 ppm attributed to —CF ₂ —CF _3. expressed.

A solid ¹⁹ F MAS NMR of a PTFE resin layer (Experimental Example A2, 500 kGy) irradiated with a radiation dose of 500 kGy was measured under the same conditions as those for the uncrosslinked PTFE resin layer, and −68 ppm and −70 ppm except for the spinning sideband. , −80 ppm, −82 ppm, −109 ppm, −112 ppm, −122 ppm, −126 ppm, −152 ppm, and −186 ppm were observed (FIG. 4 top and FIG. 4 bottom). Signals of −68 ppm, −70 ppm, −80 ppm, −109 ppm, −112 ppm, −152 ppm, and −186 ppm newly appeared upon irradiation, and the intensity of the −82 ppm signal increased from that of unirradiated.

When a solid ¹⁹ F MAS NMR of a fluororesin layer (Experimental Example A3, 1000 kGy) irradiated with a radiation dose of 1000 kGy was measured under the same conditions as those of an uncrosslinked PTFE resin layer, −68 ppm and −70 ppm except for the spinning sideband. , -77 ppm, -80 ppm, -82 ppm, -109 ppm, -112 ppm, -122 ppm, -126 ppm, -152 ppm, and -186 ppm were observed (the upper part of FIG. 5 and the lower part of FIG. 5). -68ppm, -70ppm, -77ppm, -80ppm, -109ppm, -112ppm, -152ppm, and -186ppm new signals appear by irradiation, and the signal intensity of -82ppm is higher than that at 500kGy irradiation. It was.

In the above signal, if the assigned F atom is underlined, for example, -70 ppm is = CF-C F ₃ , -109 ppm is -C F ₂ -CF (CF ₃ ) -C F _2- , -152 ppm is = C F -C F =, -186 ppm is known to be assigned to ≡C F (Beate Fuchs and Ulrich Scheler., Branching and Cross-Linking in Radiation-Modified Poly (tetrafluorethylene) Int. Macromolecules, 33, 120-124.2000).

These signals indicate the presence of chemically non-equivalent fluorine atoms and at the same time indicate that the PTFE resin layer forms a three-dimensional structure due to crosslinking. Further, according to the above document, the signal intensity of the observed signal is stronger at the irradiation dose of 1000 kGy than the irradiation dose of 500 kGy, and the signal intensity of the signal increases as the irradiation dose increases at least up to the irradiation dose of 3000 kGy. It is known to be. For signals that are not described in the above document, the structure of the fluororesin layer is considered to be different depending on the irradiation conditions of the radiation. However, the formation of a crosslinked structure means that = CF—C F ₃ and -C F ₂ -CF (CF ₃ ) -C F _2- , = C F -C F =, ≡C F and so on are clearly present.

As shown in FIG. 6, the normalized signal intensity ratio increases as the irradiation dose increases. When the irradiation dose was 500 kGy, a clearly crosslinked structure appeared, and when the irradiation dose was doubled to 1000 kGy, the normalized signal intensity ratio was about three times, indicating that the crosslinking was more advanced.

From the above, the PTFE resin gradient material has a chemical shift value (δ ppm) appearing in a solid ¹⁹ F Magic angle Spinning (MAS) nuclear magnetic resonance (NMR) chart as compared with the uncrosslinked PTFE resin. In addition to −82 ppm, −122 ppm, and −126 ppm of the resin, at least one chemical shift value selected from −68 ppm, −70 ppm, −77 ppm, −80 ppm, −109 ppm, −112 ppm, −152 ppm, and −186 ppm appears. Alternatively, it can be said that the surface layer has a three-dimensional structure in which the signal intensity of the chemical shift value appearing at −82 ppm is increased as compared with the signal intensity of the uncrosslinked PTFE resin.

After applying the aqueous coating liquid for forming the fluororesin layer used in Experimental Example A1 in a 90 ° C. constant temperature bath under drying conditions of about 30 minutes, drying, followed by baking in air at 380 ° C. for 30 minutes. Thus, an uncrosslinked fluororesin film having a thickness of 4 μm was produced. Five films were laminated in close contact, and electron beam irradiation was performed from one side under the experimental conditions of A2. After irradiation, the fluororesin film on the side opposite to the irradiated surface was separated, and NMR measurement was performed according to the above experimental example using an NMR device JNM-ECX400 manufactured by JEOL Ltd. As a result of the measurement, the signal accompanying crosslinking was in a trace state. From this, it was found that the electron beam did not reach the surface opposite to the irradiated surface but was attenuated from the irradiated surface toward the inside. From the above, it is understood that a gradient material that changes from a three-dimensional structure to a two-dimensional structure from the surface of the sliding layer toward the base material side can be obtained.

[Experiment B]
(1) Preparation of test piece Test piece: A PTFE resin layer was formed on a metal plate having a thickness of 30 mm × 30 mm and a thickness of 2 mm made by SPCC using a top coating made by Daikin (model number: EK-3700C21R). The drying time was 30 minutes in a constant temperature bath at 90 ° C., followed by baking in a heating furnace at 380 ° C. for 30 minutes.
Thereafter, the specimen was irradiated with an electron beam from the surface of the PTFE resin layer under the following conditions.
Equipment used: EPS-3000 manufactured by NHV Corporation
Acceleration voltage: 1.16MV
Irradiation dose: Experimental example B1 is 0 kGy (unirradiated), Experimental example B2 is 85 kGy, Experimental example B3 is 250 kGy, Experimental example B4 is 500 kGy, Experimental example B5 is 750 kGy, Experimental example B6 is 1000 kGy
Dose rate: Experimental example B2 is 3.9 kGy / s, Experimental example B3, Experimental example B4, Experimental example B5 and Experimental example B6 are 6.1 kGy / s
Conveyor speed: 3 m / min for experimental example B2, 2 m / min for experimental example B3 and experimental example B5, 1 m / min for experimental example B4 and experimental example B6 Coating temperature at irradiation: 310 ° C.
Atmosphere in chamber at the time of irradiation: heated nitrogen Electron flow: 8.1 mA for Experimental Example B2, 12.7 mA for Experimental Example B3, Experimental Example B4, Experimental Example B5, and Experimental Example B6
Irradiation width (conveyor moving direction): 27.5cm

(2) Test piece coating experiment example B1: PTFE coating (irradiation dose: 0 kGy, layer thickness: 20 μm)
Experimental Example B2: PTFE coating (irradiation dose: 85 kGy, layer thickness: 20 μm)
Experimental Example B3: PTFE coating (irradiation dose: 250 kGy, layer thickness: 20 μm)
Experimental Example B4: PTFE coating (irradiation dose: 500 kGy, layer thickness: 20 μm)
Experimental Example B5: PTFE coating (irradiation dose: 750 kGy, layer thickness: 20 μm)
Experimental Example B6: PTFE coating (irradiation dose: 1000 kGy, layer thickness: 20 μm)

(3) NMR measurement and result NMR measurement was carried out under the same conditions as in Experiment A using the apparatus used in Experiment A for Experimental Examples B1, B4, and B6. As a result of NMR measurement, the same NMR chart was obtained as in Experimental Example B1, Experimental Example B1, Experimental Example B4 in Experimental Example A2, and Experimental Example B6 in Experimental Example A3.
From the NMR measurement results, also in Experiment B, the cross-linked PTFE resin has a chemical shift value (δ ppm) appearing in the solid ¹⁹ F Magic angle Spinning (MAS) nuclear magnetic resonance (NMR) chart as compared to the non-cross-linked PTFE resin. In addition to -82 ppm, -122 ppm, and -126 ppm of the uncrosslinked PTFE resin, at least one chemical shift selected from -68 ppm, -70 ppm, -77 ppm, -80 ppm, -109 ppm, -112 ppm, -152 ppm, and -186 ppm It can be said that it has a three-dimensional structure in which the value appears or the signal intensity of the chemical shift value appearing at −82 ppm is increased compared to the signal intensity of the uncrosslinked PTFE resin.

In addition, after applying the aqueous coating liquid for forming the fluororesin layer used in Experimental Example B1 in a 90 ° C. constant temperature bath under drying conditions of about 30 minutes, drying in the air, in a heating furnace at 380 ° C. for 30 minutes. Firing was performed to produce an uncrosslinked fluororesin film having a thickness of 4 μm. Five films were laminated in close contact, and electron beam irradiation was performed from one surface under the conditions of Experimental Example B4. After irradiation, the fluororesin film on the side opposite to the irradiated surface was separated, and NMR measurement was performed according to the above experimental example using an NMR device JNM-ECX400 manufactured by JEOL Ltd. As a result of the measurement, a signal accompanying crosslinking was observed in the same manner as on the irradiated surface. From this, it was found that the cross-linked fluororesin layer was cross-linked from the surface to the substrate surface.

FIG. 7 shows the structure of a rolling bearing cage having the sliding layer. FIG. 7 is a perspective view of a ferrous metal cage for a rolling bearing using needle rollers as rolling elements.
The cage 1 is provided with pockets 2 for holding needle rollers, and each needle is composed of a column portion 3 positioned between the pockets and both side annular portions 4 and 5 for fixing the column portion 3. Maintain the distance between the rollers. In order to hold the needle roller, the column portion 3 is bent into a mountain fold or a valley fold at the center portion of the column portion, and has a complicated shape of a flat plate having a circular bulge in a plan view at the joint portion with both annular portions 4 and 5. It is said that. The manufacturing method of this cage is a method in which an annulus is cut out from a base material and a pocket 2 is formed by stamping by pressing, a flat plate is pressed, cut into an appropriate length, and then rolled into an annular shape. A method of joining by welding can be employed. A sliding layer of PTFE resin film is formed on the surface portion of the cage 1. The surface portion of the cage that forms the sliding layer is a portion that contacts the lubricating oil or grease, and the sliding layer is formed on the entire surface of the cage 1 including the surface of the pocket 2 that contacts the needle roller. Is preferred.

FIG. 8 is a perspective view showing a needle roller bearing which is an embodiment of a rolling bearing. As shown in FIG. 8, the needle roller bearing 6 includes a plurality of needle rollers 7 and a cage 1 that holds the needle rollers 7 at regular intervals or at unequal intervals. In the case of an engine connecting rod part bearing, no bearing inner ring and bearing outer ring are provided, and a shaft such as a crankshaft or a piston pin is directly inserted into the inner diameter side of the cage 1, and the outer diameter side of the cage 1 is a housing. It is used by being fitted into the engagement hole of a certain connecting rod. Since the needle roller 7 having no inner and outer rings and having a smaller diameter than the length is used as a rolling element, the needle roller bearing 6 is more compact than a general rolling bearing having inner and outer rings. Become.

Fig. 9 shows a longitudinal sectional view of a four-cycle engine using the needle roller bearing. FIG. 9 is a longitudinal sectional view of a four-cycle engine using a needle roller bearing as an example of the rolling bearing of the present invention. In the four-cycle engine, the intake valve 8a is opened, the exhaust valve 9a is closed, and an air-fuel mixture obtained by mixing gasoline and air is sucked into the combustion chamber 10 through the intake pipe 8, and the intake valve 8a is closed and the piston 11 is closed. And a compression stroke in which the air-fuel mixture is compressed, an explosion stroke in which the compressed air-fuel mixture is exploded, and an exhaust stroke in which the exploded combustion gas is exhausted through the exhaust pipe 9 by opening the exhaust valve 9a. The piston 11 that performs linear reciprocating motion by combustion in these strokes, the crankshaft 12 that outputs rotational motion, the connecting rod 13 that connects the piston 11 and the crankshaft 12, and converts linear reciprocating motion into rotational motion, Have The crankshaft 12 rotates about the rotation center shaft 14 and balances rotation by a balance weight 15.

The connecting rod 13 is formed by providing a large end 16 below the linear rod and a small end 17 above. The crankshaft 12 is rotatably supported via a needle roller bearing 6 a attached to the engagement hole of the large end portion 16 of the connecting rod 13. The piston pin 18 that connects the piston 11 and the connecting rod 13 is rotatably supported via a needle roller bearing 6b attached to the engagement hole of the small end portion 17 of the connecting rod 13.
By using a needle roller bearing with excellent slidability, even a two-cycle engine or a four-cycle engine reduced in size or increased in output has excellent durability.

Although FIG. 8 illustrates a needle roller bearing as the bearing, the rolling bearing of the present invention is a cylindrical roller bearing, a tapered roller bearing, a self-aligning roller bearing, a needle roller bearing, a thrust cylindrical roller bearing, or a thrust cone other than those described above. It can also be used as a roller bearing, a thrust needle roller bearing, a thrust spherical roller bearing, a foil bearing and the like. In particular, it can be suitably used for a rolling bearing that is used in an oil-lubricated environment and uses a ferrous metal material cage.

Example 1 and Comparative Example 1
A needle bearing cage (base surface hardness Hv: 484 to 595) made of chromium molybdenum steel (SCM415) φ44 mm × width 22 mm, which has been quenched and tempered, was prepared and used for the formation of the PTFE resin layer used in Experimental Example A1. The PTFE surface sliding layer was coated, dried, and fired under the same conditions as in Experimental Example A1, except that the coating liquid was the same as the coating liquid and the thickness of the coating layer was changed to the thickness shown in Table 1. Using the electron beam irradiation apparatus used in Experimental Example A2, the electron beam irradiation is performed with the irradiation dose shown in Table 1, and the PTFE inclination of the three-dimensional structure to the two-dimensional structure is directed from the surface of the coating layer to the surface on the substrate side. Material was used. In the material column of the sliding layer in Table 1, “two-dimensional → three-dimensional PTFE” represents a PTFE structure from the surface on the substrate side to the surface. Comparative Example 1 was not irradiated as in Experimental Example A1.

The surface treated needle bearing cage was evaluated by the following method. An outline of the wear amount test apparatus is shown in FIG.
In a state where a concave mating member 19 made of SUJ2 and quenched and tempered HRC62 and having a concave surface roughness of 0.1 to 0.2 μmRa is pressed from the vertical direction to the cage 1 attached to the rotary shaft with a predetermined load 20, together with the rotary shaft The friction characteristics of the coating applied to the surface of the cage 1 were evaluated by rotating the cage 1, and the amount of wear was measured. The measurement conditions are load: 440 N, lubricating oil: mineral oil (10W-30), sliding speed: 930.6 m / min, measurement time: 100 hours. Moreover, the adhesiveness of the PTFE coating was also evaluated by visually observing the amount of peeling at that time. The peeling amount is “large” when the peeling area at the maximum peeling location is 1 mm ² or more, and the “small” is when the peeling area at the maximum peeling location is less than 1 mm ² . The radius of the concave R portion was set to a size 20 to 55 μm larger than the cage radius. Lubricating oil was used in an amount soaking up to half the height of the cage. The results are shown in Table 1.

The cage for rolling bearings of the present invention can suppress wear even under conditions of high sliding speed and high surface pressure in lubricating oil, and is particularly used in lubricating oil using a ferrous metal material cage. And can be used in the field of rolling bearings using this cage.

DESCRIPTION OF SYMBOLS 1 Cage 2 Pocket 3 Column part 4 Ring part 5 Ring part 6 Needle roller bearing 7 Needle roller 8 Intake pipe 9 Exhaust pipe 10 Combustion chamber 11 Piston 12 Crankshaft 13 Connecting rod 14 Rotation center axis 15 Balance weight 16 Large End 17 Small end 18 Piston pin 19 Concave mating material 20 Load 21 Sliding layer 22 Metal base 23 Surface not in contact with metal base 24 Surface in contact with metal base

Claims (8)

1. A rolling bearing retainer for holding rolling elements of a rolling bearing used in an oil lubricated environment,
   The rolling bearing retainer has a base material and a sliding layer formed on the surface of the base material,
   A rolling bearing, wherein the sliding layer is a fluororesin layer, and the fluororesin present on the surface of the sliding layer that is not in contact with the base material of the fluororesin layer and in the vicinity thereof has at least a three-dimensional structure. Retainer.
2. The rolling bearing retainer according to claim 1, wherein the surface of the fluororesin that is in contact with the base material and the fluororesin present in the vicinity thereof have a two-dimensional structure.
3. The rolling bearing holding according to claim 2, wherein the content of the three-dimensional structure of the fluororesin continuously decreases from the surface of the sliding layer toward the surface in contact with the base material. vessel.
4. The rolling bearing cage according to claim 1, wherein the three-dimensional structure of the fluororesin is continuous from the surface of the sliding layer toward the surface in contact with the base material.
5. The rolling bearing retainer according to claim 1, wherein the fluororesin is a polytetrafluoroethylene resin.
6. The rolling bearing cage according to claim 1, wherein the sliding layer has a thickness of 5 μm or more and less than 40 μm.
7. The rolling bearing retainer according to claim 1, wherein the base material is a ferrous metal material.
8. A rolling bearing using the rolling bearing cage according to claim 7.

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