Wet lubrication sliding members, bearing cages, and rolling bearings

Abstract

To provide a sliding member for wet lubrication in which a friction coefficient is small, sliding heat generation is suppressed, and durability is excellent under high-speed sliding conditions of a wet lubrication method, a holder for a bearing comprising the sliding member for wet lubrication, and a rolling bearing comprising the holder for a bearing.SOLUTION: In a sliding member for wet lubrication made of a molded body of a resin composition containing (A) a polyester aromatic ketone resin, (B) carbon fibers with an average fiber length of 1 mm or more, and (C) reinforcing fibers with an average fiber length of 300 μm or less, the surface roughness (Sz) of the sliding member is 60 μm or less, and the flexural modulus of the sliding member is 12 GPa or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sliding member for wet lubrication, a cage for a bearing, and a rolling bearing. [Background technology]

[0002] Amidst worsening environmental problems caused by greenhouse gas emissions and other factors, the widespread adoption of electric vehicles (EVs), which have a lower environmental impact, is highly anticipated. One of the key challenges to the widespread adoption of EVs is extending their driving range, which requires space to accommodate larger batteries.

[0003] In recent years, driven by the need for smaller and lighter drive systems and higher output drive motors for electric vehicles, which directly contribute to improved fuel and energy efficiency, rolling bearings for motor support are required to have performance capabilities at high rotational speeds that are even greater than before. Specifically, when high-speed rolling bearings for electric vehicle drive motors are rotated at high speeds, problems include seizure due to poor lubrication caused by heat generation from sliding, deformation and damage to components due to deformation of the bearing cage (retainer) caused by centrifugal force, and vibration and abnormal noise during sliding.

[0004] Patent Document 1 discloses an invention relating to a rolling bearing that rotatably supports the rotating shaft of a turbomachinery, characterized in that the inside of the bearing is lubricated by rolling elements guided by a wet lubrication method using an oily lubricant such as air-oil lubrication or oil mist lubrication. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-155376 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, even in the bearing described in Patent Document 1, under high-speed sliding conditions with a wet lubrication system, the coefficient of friction and heat generated by sliding were large, resulting in insufficient durability.

[0007] The object of the present invention is to provide a wet lubrication sliding member that has a low coefficient of friction, suppresses sliding heat generation, and has excellent durability under high-speed sliding conditions of a wet lubrication system, a bearing retainer equipped with the sliding member, and a rolling bearing equipped with the bearing retainer. [Means for solving the problem]

[0008] The present inventors, with the aim of solving the above problems, conducted extensive research and have found that a sliding member made of a molded article of a resin composition containing a polyether aromatic ketone resin, carbon fibers with an average fiber length of 1 mm or more, and reinforcing fibers with an average fiber length of 300 μm or less, can be obtained with a surface roughness (Sz) of 60 μm or less and a flexural modulus of 12 GPa or more, thereby providing a sliding member with a low coefficient of friction, suppressed heat generation during sliding, and excellent durability under high-speed sliding conditions using a wet lubrication system. This led to the completion of the present invention. In other words, the gist of the present invention is as follows.

[0009] Item 1 A wet lubrication sliding member comprising a molded article of a resin composition containing (A) a polyether aromatic ketone resin, (B) carbon fibers having an average fiber length of 1 mm or more, and (C) reinforcing fibers having an average fiber length of 300 μm or less, characterized in that the surface roughness (Sz) of the sliding member is 60 μm or less, and the flexural modulus of the sliding member is 12 GPa or more.

[0010] Item 2 The wet lubrication sliding member according to Item 1, characterized in that the average fiber length of the reinforcing fibers is 1 μm to 300 μm.

[0011] Item 3: The wet lubrication sliding member according to Item 1 or 2, characterized in that the Mohs hardness of the reinforcing fiber is 5 or less.

[0012] Item 4 The wet lubrication sliding member according to any one of items 1 to 3, wherein the reinforcing fiber is potassium titanate fiber or wollastonite fiber.

[0013] Item 5: A wet lubrication sliding member according to any one of Items 1 to 4, characterized in that the average fiber length of the carbon fibers is 1 mm to 30 mm.

[0014] Item 6 A wet lubrication sliding member according to any one of Items 1 to 5, characterized in that the tensile modulus of the carbon fiber is 190 GPa to 300 GPa.

[0015] Item 7 A wet lubrication sliding member according to any one of Items 1 to 6, characterized in that the carbon fiber is a polyacrylonitrile-based carbon fiber.

[0016] Item 8 A wet lubrication sliding member according to any one of Items 1 to 7, characterized in that the carbon fiber content is less than 30% by mass in 100% by mass of the resin composition.

[0017] Item 9 A bearing cage that constitutes a rolling bearing together with an inner ring, an outer ring, and rolling elements, and rotatably holds the rolling elements, characterized in that it comprises a wet lubrication sliding member as described in Items 1 to 8.

[0018] A rolling bearing characterized by comprising the bearing cage described in item 10, item 9. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a sliding member with a low coefficient of friction, suppressed heat generation during sliding, and excellent durability under high-speed sliding conditions using a wet lubrication system, a bearing cage equipped with the sliding member, and a rolling bearing equipped with the bearing cage. [Brief explanation of the drawing]

[0020] [Figure 1] Figure 1 is a schematic cross-sectional view showing a rolling bearing according to one embodiment of the present invention.

Best Mode for Carrying Out the Invention

[0021] Hereinafter, an example of a preferred embodiment of the present invention will be described. However, the following embodiments are merely illustrative, and the present invention is not limited to the following embodiments in any way.

[0022] The sliding member for wet lubrication according to the present invention is a member that slides under wet lubrication using a grease lubricant or an oil lubricant, and preferably a member that slides under wet lubrication using an oil lubricant. Examples of the oil lubricant include lubricating oils such as mineral oils such as engine oil, spindle oil, turbine oil, machine oil, cylinder oil, and gear oil; vegetable oils such as castor oil; animal oils such as whale oil; and synthetic oils such as silicone. These are used alone or in combination of two or more as necessary.

[0023] The sliding member is a molded body of a resin composition containing (A) a polyether aromatic ketone resin, (B) carbon fibers having an average fiber length of 1 mm or more, and (C) reinforcing fibers having an average fiber length of 300 μm or less. Here, in the present specification, a member molded from a resin composition containing fillers (B) and (C) in (A) a polyether aromatic ketone resin is also referred to as a "sliding member". The sliding member is generally manufactured by injection molding, but can also be manufactured by cutting or other processing methods.

[0024] In the present invention, the surface roughness (Sz) of the sliding member is 60 μm or less, preferably 25 μm or less. Also, it is preferably 12 μm or more, more preferably 16 μm or more.

[0025] In the present specification, the surface roughness (Sz) of the sliding member is the three-dimensional surface roughness defined in ISO 25178, and refers to the maximum height within the measurement target area, that is, the distance in the height direction from the highest point to the lowest point. The surface roughness (Sz) can be measured using a laser microscope, and specific operation measurement conditions are appropriately set according to the measurement object and the measurement device.

[0026] In the present invention, the flexural modulus of the sliding member is 12 GPa or more, preferably 14 GPa or more. The upper limit of the flexural modulus of the sliding member is not particularly limited, but for example, it is 17 GPa. In this specification, the flexural modulus of the sliding member is measured in accordance with JIS K7272.

[0027] By keeping the surface roughness (Sz) and flexural modulus of the sliding member within the above range, a low coefficient of friction, suppression of sliding heat generation, and excellent durability can be obtained under high-speed sliding conditions in a wet lubrication system. Furthermore, because the sliding member of the present invention has excellent sliding properties, it can be used without coating the sliding surface of the member.

[0028] The components of the wet lubrication sliding member of the present invention will be described in more detail below.

[0029] <Resin composition> The resin composition used in the present invention contains (A) a polyether aromatic ketone resin, (B) carbon fibers with an average fiber length of 1 mm or more, and (C) reinforcing fibers with an average fiber length of 300 μm or less, and may further contain (D) barium sulfate and other additives as needed.

[0030] The constituent components of the resin composition used in the present invention will be described below.

[0031] ((A) Polyether aromatic ketone resin) The polyether aromatic ketone resin contained in the resin composition used in the present invention is a thermoplastic resin whose structural units include aromatic nuclear bonds, ether bonds, and ketone bonds.

[0032] Specific examples, though not limited to them, include polyarylene ketone resins such as polyetherketone (PEK) resin, polyetheretherketone (PEEK) resin, polyetherketoneketone (PEKK) resin, and polyetheretherketoneketone (PEEKK) resin.

[0033] In particular, PEEK resin having repeating units represented by the following general formula (1) is preferably used.

[0034] [ka]

[0035] Furthermore, the PEEK resin may contain, along with the basic repeating unit (1) described above, one or more repeating units represented by the following general formula (2), as long as they do not impair the essential properties of the present invention.

[0036] [ka]

[0037] Examples of commercially available PEEK resins include those manufactured by VICTREX, such as "PEEK151G," "PEEK381G," and "PEEK450G."

[0038] In the present invention, one type of polyether aromatic ketone resin may be used alone, or two or more types may be used in combination. The polyether aromatic ketone resin has a shear rate of 1.0 × 10⁻⁶ measured at a melting temperature 57°C higher than its melting point using a capillary rheometer. 3 sec -1 The melt viscosity at is 1.0 × 10 5 mPa·s ~4.0 × 10 5 A value of mPa·s is preferred.

[0039] ((B) Carbon fiber) The carbon fibers used in the resin composition of the present invention can include, for example, polyacrylonitrile (PAN)-based, pitch-based, cellulose-based, hydrocarbon-based vapor-grown carbon fibers, graphite fibers, etc. These may be used individually or in combination of two or more types. Preferably, polyacrylonitrile-based carbon fibers are preferred from the viewpoint of further improving mechanical strength and sliding properties.

[0040] In the present invention, the average fiber length of the carbon fibers is 1 mm or more, preferably 3 mm or more. By setting the average fiber length of the carbon fibers to be above the lower limit, an even better flexural modulus (rigidity) can be obtained. Furthermore, from the viewpoint of moldability, the carbon fibers are preferably discontinuous fibers such as chopped fibers (short fibers), and the average fiber length of the carbon fibers is preferably 30 mm or less, more preferably 15 mm or less, and even more preferably 10 mm or less.

[0041] The carbon fibers contained in the resin composition used in the present invention preferably have an average fiber diameter of 1 μm to 50 μm, and more preferably 3 μm to 20 μm. When the average fiber diameter is within this range, even if the carbon fiber content in the resin composition used in the present invention is increased, the decrease in fluidity can be further suppressed. The carbon fibers may be bundled together with a consolidating agent or the like if they have the above average fiber diameter.

[0042] In this invention, the tensile modulus of the carbon fiber is preferably 190 GPa to 300 GPa, and more preferably 230 GPa to 300 GPa. If the tensile modulus of the carbon fiber is too low, the reinforcing effect of the carbon fiber on the sliding interface is small, and excessive friction powder may be generated, potentially leading to an unstable coefficient of friction. On the other hand, if the tensile modulus is too high, the detached material at the sliding interface may create significant resistance. The tensile modulus of the carbon fiber is shown as the value measured in accordance with Method A of JIS R7606 (2000).

[0043] In the resin composition used in the present invention, from the viewpoint of further improving rigidity performance such as the flexural modulus when used as a sliding member for wet lubrication, and further improving fluidity, it is preferable that the carbon fiber content be 15% by mass or more, more preferably 20% by mass or more, and even more preferably less than 30% by mass. When the carbon fiber content is 30% by mass or more, the surface smoothness deteriorates, and sufficient sliding characteristics (low coefficient of friction, suppression of sliding heat generation, durability, etc.) may not be obtained.

[0044] ((C) Reinforced Fiber) The reinforcing fibers included in the resin composition used in the present invention are not particularly limited, but are preferably inorganic fibers. From the viewpoint of further improving the sliding properties of the sliding member, inorganic fibers with a Mohs hardness of 5 or less are preferred. Mohs hardness is an index representing the hardness of a substance; substances that are scratched when rubbed against other minerals have lower hardness. Examples of inorganic fibers with a Mohs hardness of 5 or less include potassium titanate fibers, wollastonite fibers, zinc oxide, basic magnesium sulfate, alumina fibers, silicon carbide fibers, and boron fibers. These reinforcing fibers may be used individually or in combination of multiple types.

[0045] The reinforcing fibers are preferably a powder composed of fibrous particles. From the viewpoint of further reducing surface roughness (Sz) while further increasing the flexural modulus, the average fiber length is 300 μm or less, preferably 1 μm to 300 μm, more preferably 1 μm to 200 μm, even more preferably 3 μm to 100 μm, and particularly preferably 5 μm to 50 μm. The average aspect ratio is preferably 3 to 200, more preferably 3 to 100, even more preferably 3 to 50, and particularly preferably 3 to 40.

[0046] In this invention, a fibrous particle is defined as a particle in which, when the longest side of the rectangular parallelepiped with the smallest volume among the rectangular parallelepipeds circumscribed around the particle (circumscribed rectangular parallelepiped) is defined as the major axis L, the next longest side as the minor axis B, and the shortest side as the thickness T (B > T), both L / B and L / T are 3 or more, with the major axis L corresponding to the fiber length and the minor axis B corresponding to the fiber diameter.

[0047] From the viewpoint of further reducing surface roughness (Sz) and further improving sliding properties, the reinforcing fibers are preferably at least one of potassium titanate fibers and wollastonite fibers, more preferably potassium titanate fibers or wollastonite fibers, and particularly preferably potassium titanate fibers. Examples of potassium titanate fibers include single crystal fibers represented by the general formula K2O·nTiO2 (where n is an integer from 2 to 8) or the general formula K2O·nTiO2·1 / 2H2O (where n is an integer from 2 to 8). Specific examples include 4-potassium titanate fibers, 6-potassium titanate fibers, 8-potassium titanate fibers, and mixtures thereof.

[0048] The dimensions of the potassium titanate fibers are not particularly limited as long as they are within the above-mentioned range, but the average fiber length is preferably 1 μm to 50 μm, more preferably 3 μm to 30 μm, and even more preferably 3 μm to 20 μm. The average fiber diameter is preferably 0.01 μm to 1 μm, more preferably 0.05 μm to 0.8 μm, and even more preferably 0.1 μm to 0.7 μm. The average aspect ratio is preferably 10 or more, more preferably 10 to 100, and even more preferably 15 to 35. These reinforcing fibers can be commercially available products, for example, "TISMO D" (average fiber length 15 μm, average fiber diameter 0.5 μm) and "TISMO N" (average fiber length 15 μm, average fiber diameter 0.5 μm) manufactured by Otsuka Chemical Co., Ltd. can be used.

[0049] The wollastonite fibers are inorganic fibers made of calcium metasilicate, and conventionally known fibers can be widely used. The dimensions of the wollastonite fibers are not particularly limited as long as they are within the range of the dimensions of the reinforcing fibers described above, but the average fiber length is preferably 5 μm to 180 μm, more preferably 10 μm to 100 μm, and even more preferably 20 μm to 40 μm. The average fiber diameter is preferably 0.1 μm to 15 μm, more preferably 1 μm to 10 μm, and even more preferably 2 μm to 7 μm. The average aspect ratio is preferably 3 or more, more preferably 3 to 30, and even more preferably 3 to 15. These reinforcing fibers can be commercially available products, for example, "Bystal W" (average fiber length 25 μm, average fiber diameter 3 μm) manufactured by Otsuka Chemical Co., Ltd. can be used.

[0050] The average fiber length and average fiber diameter mentioned above can be measured by observation with a scanning electron microscope, and the average aspect ratio (average fiber length / average fiber diameter) can be calculated from the average fiber length and average fiber diameter. For example, by photographing multiple reinforcing fibers with a scanning electron microscope, 300 reinforcing fibers can be arbitrarily selected from the observed images, their fiber lengths and fiber diameters can be measured, and the average fiber length can be obtained by summing all the fiber lengths and dividing by the number of fibers, and the average fiber diameter can be obtained by summing all the fiber diameters and dividing by the number of fibers.

[0051] In the resin composition used in the present invention, from the viewpoint of surface smoothness, the reinforcing fiber content is preferably 0.5% by mass or more, more preferably 5% by mass or more, and from the viewpoint of rigidity, it is preferably less than 20% by mass.

[0052] The mass ratio of carbon fibers to reinforcing fibers ((B) carbon fibers / (C) reinforcing fibers) in the resin composition used in the present invention is preferably 0.75 to 60, more preferably 0.75 to 6, and even more preferably 1 to 6. By setting the mass ratio of carbon fibers to reinforcing fibers within the above range, the surface smoothness of the sliding member molded from the resin composition used in the present invention can be further enhanced while increasing the rigidity of the sliding member, thereby further improving the sliding characteristics under high-speed sliding conditions with wet lubrication.

[0053] <Optional components of the resin composition used in the present invention> (Barium(D) sulfate) The resin composition used in the present invention may optionally contain barium(D) sulfate (hereinafter sometimes referred to as "component (D)"). Component (D) includes elutriated barium sulfate (barite powder) obtained by crushing a mineral called barite, washing it to remove iron, and elutriating it, and precipitated barium sulfate which is artificially synthesized. The particle size of precipitated barium sulfate can be controlled by the conditions during synthesis, making it possible to produce fine barium sulfate with a low content of coarse particles. From the viewpoint of further reducing impurities and making the particle size distribution more uniform, it is preferable to use precipitated barium sulfate.

[0054] Component (D) is preferably in powder form, with an average particle size preferably 0.1 μm to 50 μm, more preferably 0.1 μm to 30 μm, even more preferably 0.1 μm to 5 μm, even more preferably 0.3 to 1.2 μm, particularly preferably 0.3 μm to 0.8 μm, and most preferably 0.3 μm to 0.5 μm. By setting the average particle size within the above range, the coefficient of friction during sliding can be further reduced.

[0055] The average particle diameter of component (D) can be measured by laser diffraction and scattering, and the particle diameter at 50% volume-based cumulative particle size distribution measured by laser diffraction and scattering (50% volume-based cumulative particle diameter) is D 50 This is the median diameter. This volume-based cumulative 50% particle size (D 50 ) is the particle diameter at the point where the cumulative value reaches 50%, obtained by counting the number of particles from smallest to largest on a cumulative curve where the total volume is set to 100% after determining the particle size distribution based on volume.

[0056] The particle shape of component (D) is not particularly limited as long as it is a non-fibrous particle such as spherical, columnar, plate-shaped, rod-shaped, cylindrical, block-shaped, or irregularly shaped, but is preferably spherical, plate-shaped, or irregularly shaped. The particle shape of barium sulfate can be analyzed, for example, by scanning electron microscopy (SEM) observation.

[0057] The content of component (D) in the resin composition used in the present invention is preferably 1% to 30% by mass, more preferably 1% to 20% by mass, even more preferably 1% to 15% by mass, and most preferably 1.5% to 2.5% by mass, based on 100% by mass of the total amount of the resin composition used in the present invention.

[0058] (Other additives) The resin composition used in the present invention may contain other additives, as long as they do not impair its desirable physical properties. Other additives include non-fibrous inorganic fillers (e.g., calcium carbonate, mica, sericite, illite, talc, kaolinite, montmorillonite, boehmite, smectite, vermiculite, palygorskite, pyrophyllite, hylosite, diatomaceous earth, titanium dioxide, potassium titanate, sodium titanate, magnesium potassium titanate, lithium potassium titanate, etc.); conductive fillers (e.g., metal particles (e.g., aluminum flakes), metal fibers, metal oxide particles, carbon particles (e.g., graphite, expanded graphite, flaky graphite, graphene, carbon black, graphitized carbon black), carbon nanotubes, etc.); antistatic agents; antioxidants and heat stabilizers; ultraviolet absorbers; light stabilizers; weathering agents; lightfasteners; mold release agents; lubricants; flow modifiers; plasticizers; impact modifiers; flame retardants; dripping inhibitors; nucleating agents; dispersants; vibration dampers; neutralizing agents; blocking inhibitors, etc., and one or more of these may be included.

[0059] If the resin composition used in the present invention contains other additives, the amount of such additives is not particularly limited as long as it does not impair the desirable physical properties of the wet lubrication sliding member according to the present invention. The amount of additives is 10% by mass or less, preferably 5% by mass or less, of the total amount of the resin composition (100% by mass).

[0060] <Method for producing the resin composition used in the present invention> The resin composition used in the present invention can be produced by mixing and heating (especially by melt kneading) a mixture containing (A) a polyether aromatic ketone resin, (B) carbon fibers with an average fiber length of 1 mm or more, (C) reinforcing fibers with an average fiber length of 300 μm or less, and (D) barium sulfate and other additives.

[0061] For melt mixing, known melt mixing equipment such as a twin-screw extruder can be used. Specifically, it can be manufactured by (1) pre-mixing each component in a mixer (tumbler, Henschel mixer, etc.), melt mixing in a melt mixing equipment, and pelletizing with pelletizing means (pelletizer, etc.); (2) preparing a masterbatch of the desired components, mixing in other components as needed, melt mixing in a melt mixing equipment, and pelletizing; or (3) supplying each component to a melt mixing equipment and pelletizing.

[0062] The processing temperature in melt mixing is not particularly limited as long as it is a temperature at which the (A) polyether aromatic ketone resin can melt. Typically, the cylinder temperature of the melt mixing apparatus used for melt mixing is adjusted to this range. Thus, a resin composition used in the present invention that exhibits the desired effect is produced.

[0063] <Manufacturing method and applications of sliding members for wet lubrication> The resin composition used in the present invention can be molded into various types of molded articles by known resin molding methods such as injection molding, insert molding, compression molding, blow molding, and inflation molding, depending on the type, application, and shape of the target molded article, with injection molding and insert molding being preferred. A molding method combining the above molding methods can also be employed. The sliding member obtained by molding the resin composition used in the present invention can be a member with a low coefficient of friction, suppressed sliding heat generation, and excellent durability under high-speed sliding conditions of a wet lubrication system. For this reason, the wet lubrication sliding member obtained by molding the resin composition used in the present invention is suitably used, for example, in the manufacture of sliding components constituting rolling bearings for electric vehicle drive motors used in high-speed rotation (sliding) regions.

[0064] The lubrication methods for wet-lubricated sliding members of the present invention are broadly classified into grease lubrication, which lubricates the member with a grease lubricant sealed in the internal space of the bearing (the annular space between the inner and outer rings), and oil lubrication, which lubricates the member with an oily lubricant that is successively supplied from outside the bearing into the internal space of the bearing. However, since it is necessary to improve lubrication and cooling efficiency, the oily lubrication method is preferred for the wet-lubricated sliding members of the present invention. Furthermore, oily lubrication methods are broadly classified into jet lubrication, under-race lubrication, air-oil lubrication, oil mist lubrication, etc. However, since the amount of oily lubricant supplied per unit time is significantly smaller and the amount of oily lubricant used (cost required for lubrication) can be suppressed, the oily lubrication method applied to the wet-lubricated sliding members of the present invention is preferably air-oil lubrication or oil mist lubrication.

[0065] One embodiment of the present invention is a bearing cage equipped with a wet lubrication sliding member of the present invention that constitutes a rolling bearing together with an inner ring, an outer ring, and rolling elements, and rotatably holds the rolling elements. Furthermore, the component is suitably used as a component used in the manufacture of the bearing cage.

[0066] Figure 1 is a schematic cross-sectional view showing a rolling bearing according to one embodiment of the present invention. As shown in Figure 1, the rolling bearing 1 comprises an inner ring 2, an outer ring 3, rolling elements 4, and a bearing cage 10. The bearing cage 10 is composed of the wet lubrication sliding member of the present invention described above.

[0067] The bearing cage 10 can have countless recesses for holding lubricating oil on at least one of its inner diameter surface 10a and the pocket surface 11a of the pocket portion 11. In this way, lubricating oil can be efficiently held, so even if the amount of lubricating oil supplied to the internal space of the bearing is small, the oil film formation performance on the pocket surface 11a can be improved, and wear of the bearing cage 10 can be effectively prevented.

[0068] Furthermore, since the bearing cage 10 is constructed from the wet lubrication sliding member of the present invention described above, the recess can be easily formed by providing a mold portion for the convex portion corresponding to the recess in the molding die of the bearing cage 10. The pocket surface 11a of the pocket portion 11 can be formed, for example, on a surface parallel to the center line of the pocket portion 11. Also, the contour line of the pocket portion 11 can be formed in a rectangular shape.

[0069] Another embodiment of the present invention is a rolling bearing for an electric vehicle drive motor that includes the above-mentioned bearing cage as a component. The above-mentioned rolling bearing for an electric vehicle drive motor comprises an inner ring having an inner raceway surface and mounted on the rotating shaft of the electric vehicle drive motor, an outer ring having an outer raceway surface, a plurality of rolling elements arranged to roll freely between the inner and outer raceway surfaces, and a bearing cage positioned between the inner and outer rings and having a plurality of pockets that individually hold the plurality of rolling elements, and the inside of the bearing is lubricated by a lubrication method such as air-oil lubrication or oil mist lubrication, wherein the inner and outer rings are formed from steel tempered at 400°C or higher, the rolling elements are formed from steel or ceramics tempered at 400°C or higher, and the bearing cage is formed from the wet lubrication sliding member of the present invention and is guided by the rolling elements. Note that the term "rotating shaft" is a concept that includes not only the main shaft of the electric vehicle drive motor but also a driven rotating shaft that rotates in response to the rotation of this main shaft.

[0070] As described above, forming the inner and outer rings from steel tempered at 400°C or higher minimizes strength reduction and dimensional changes within the operating temperature range of electric vehicle drive motor bearings (approximately 80°C to 350°C). Furthermore, forming the rolling elements from the same steel as the raceway rings minimizes strength reduction and dimensional changes of the rolling elements. The rolling elements may also be made of ceramics, in which case, in addition to the above characteristics, rolling elements with low heat generation and excellent resistance to smearing can be obtained. Moreover, since the wet lubrication sliding member of the present invention has excellent mechanical strength, especially rigidity, forming a bearing cage using it as a component and using rolling element guides for the bearing cage allows for avoidance of contact and sliding between the inner or outer ring and the bearing cage, even when the inner or outer ring rotates at high speed under lubrication methods where the supply of lubricating oil to the inside of the bearing is insufficient, such as air-oil lubrication or oil mist lubrication. This makes it possible to prevent as much as possible from malfunctions such as wear and seizure in the inner ring, outer ring, and bearing cage.

[0071] Combined with the above functions and effects, even when the rolling bearing of the present invention is used under severe conditions with a shortage of lubricating oil supply under the high-speed sliding conditions of the wet lubrication method, it can stably exhibit predetermined bearing performance over a long period of time and is characterized by being highly reliable.

[0072] Among the components of the rolling bearing of the present invention, it is preferable to use balls or cylindrical rollers as rolling elements.

[0073] According to the present invention, when the rolling bearing is rotated (slid) at high speed, the friction coefficient is small, sliding heat generation is suppressed, and it has excellent heat resistance and durability. In addition, the cage for bearings provided with the sliding member for wet lubrication of the present invention can be expected to reduce deformation and breakage due to the centrifugal force of the rolling elements during high-speed sliding, as well as reduce vibration and abnormal noise.

Examples

[0074] Specific descriptions will be given below based on examples and comparative examples, but it is not limited thereto as long as the gist of the present invention is not impaired. The raw materials used in the present examples and comparative examples are specifically as follows.

[0075] Polyether ether ketone (PEEK) resin: melt viscosity 3.5×10 5 mPa·s, melting point 343°C (manufactured by Victrex, trade name "PEEK450G") Carbon fiber: polyacrylonitrile (PAN) - based carbon fiber, tensile elastic modulus 294 GPa, average fiber length 6 mm, average fiber diameter 5 μm (manufactured by Nippon Polymer Co., Ltd., trade name: "CFAU3") Potassium titanate fiber: average fiber length 15 μm, average fiber diameter 0.5 μm (manufactured by Otsuka Chemical Co., Ltd., trade name "Tismo N102")

[0076] The melt viscosity of the polyether ether ketone (PEEK) resin was measured at 400°C using a melt viscosity measuring device (manufactured by Toyo Seiki Seisakusho Co., Ltd., trade name "Capillograph 1D") with a shear rate of 1.0×10 3 sec -1The melt viscosity was measured using a 1.0 mmφ × 10 mm capillary rheometer under the specified conditions.

[0077] <Examples 1-4 and Comparative Examples 1-4> Pellets were produced by melt-kneading the materials using a twin-screw extruder according to the mixing ratios shown in Table 1. The cylinder temperature of the twin-screw extruder was 380°C.

[0078] The obtained pellets were used to produce JIS test specimens (bending test specimens) and friction and wear test specimens (hollow cylinders with an outer diameter of 25.6 mm, an inner diameter of 20 mm, and a height of 15 mm) by injection molding. The cylinder temperature of the injection molding machine was 400°C, and the mold temperature was 180°C.

[0079] <Rating> (Tensile strength) The tensile strength was measured in accordance with JIS K7162.

[0080] (Bending strength, bending modulus) In accordance with JIS K7271, bending strength and bending modulus were measured using an Autograph AG-5000 (manufactured by Shimadzu Corporation) in a three-point bending test with a support distance of 60 mm. The results are shown in Table 1.

[0081] (Surface roughness) Surface roughness Sz was measured on the sliding surface of a friction abrasion test specimen before friction abrasion testing using a KEYENCE product name "Shape Analysis Laser Microscope," model number "VK-X250," with an objective lens of 10x and a measurement area of ​​1060 μm × 1425 μm. Surface roughness Sz (maximum height) was measured from the maximum height and maximum valley depth.

[0082] (Friction and wear test) For the friction and wear test specimens prepared as described above, the average value of the friction coefficient at a stable state, the temperature of the mating steel, and the distance until melt were measured using a Suzuki friction and wear tester (EFM-III-F, manufactured by A&D Company, Limited) in accordance with JIS K7218 Method A, from 10 minutes after the start of the test until the end of the test. The test conditions were as follows: the surface of the friction and wear test specimen was coated with ATF fluid oil (ATF grade: TYPE-TIV) manufactured by Toyota Motor Corporation, with a surface pressure of 0.2 MPa, a peripheral speed of 4 m / sec, and a driving distance of 300 km or more. The mating steel was carbon steel for machine structures (S45C) (the sliding surface was polished with #1000 sandpaper), and the test time was defined as the time until the sliding member (friction and wear test specimen) melted.

[0083] [Table 1]

[0084] As is clear from Table 1, in the wet lubrication sliding members of Examples 1 to 4, which are molded articles of a resin composition containing a polyether aromatic ketone resin, carbon fibers with an average fiber length of 1 mm or more, and reinforcing fibers with an average fiber length of 300 μm or less, and in which the surface roughness (Sz) of the molded article is 60 μm or less and the flexural modulus is in the range of 12 GPa or more, it can be seen that the coefficient of friction is small, the heat generation of the mating steel material is suppressed, and the durability distance to melt is increased. On the other hand, in the wet lubrication sliding members of Comparative Examples 1 to 4, in which the surface roughness (Sz) of the molded article is 60 μm or less and the flexural modulus is not in the range of 12 GPa or more, the test results for durability distance to melt were not sufficient. From these results, it was found that the sliding members of the present invention exhibit the unexpected effect of excellent durability.

[0085] Therefore, the wet lubrication sliding members molded from the resin composition used in the present invention have a low coefficient of friction, suppressed heat generation during sliding, and excellent durability, making them suitable for use in bearing cages, rolling bearings equipped with such bearing cages, and the like, which are used under high-speed sliding conditions of wet lubrication. [Explanation of symbols]

[0086] 1…Rolling bearings 2…Inner circle 3…Outer ring 4... Rolling element 10...Bearing cage 10a...Inner diameter surface 11…Pocket section 11a...Pocket side

Claims

1. A wet lubrication sliding member comprising a molded article of a resin composition containing (A) a polyether aromatic ketone resin, (B) carbon fibers with an average fiber length of 1 mm or more, and (C) reinforcing fibers with an average fiber length of 300 μm or less, The reinforcing fiber is potassium titanate fiber, The carbon fiber content is 15% by mass or more and less than 30% by mass in 100% by mass of the resin composition. The content of the reinforcing fibers is 0.5% by mass or more and less than 20% by mass in 100% by mass of the resin composition. The mass ratio of the carbon fibers to the reinforcing fibers contained in the resin composition ((B) carbon fibers / (C) reinforcing fibers) is 1 to 6. A sliding member for wet lubrication, characterized in that the surface roughness (Sz) of the sliding surface of the sliding member is 16 μm or more and 25 μm or less, and the flexural modulus of the sliding member is 12 GPa or more and 17.9 GPa or less.

2. The wet lubrication sliding member according to claim 1, characterized in that the average fiber length of the reinforcing fibers is 1 μm to 300 μm.

3. The wet lubrication sliding member according to claim 1 or claim 2, characterized in that the average fiber length of the carbon fibers is 1 mm to 30 mm.

4. A wet lubrication sliding member according to any one of claims 1 to 3, characterized in that the tensile modulus of the carbon fiber is 190 GPa to 300 GPa.

5. A wet lubrication sliding member according to any one of claims 1 to 4, characterized in that the carbon fiber is a polyacrylonitrile-based carbon fiber.

6. In a bearing cage that constitutes a rolling bearing together with an inner ring, an outer ring, and rolling elements, and which rotatably holds the rolling elements, A bearing cage characterized by comprising a wet lubrication sliding member as described in any one of claims 1 to 5.

7. A rolling bearing characterized by comprising the bearing cage described in claim 6.

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