Cages for rolling bearings and rolling bearings

Abstract

To provide a holder for a rolling bearing excellent in heat resistance and capable of realizing good moldability even when the holder is thick, and a rolling bearing using the holder.SOLUTION: A holder 5 is a toric holder for a rolling bearing made by injection molding of a resin composition and having a plurality of pockets 6 for holding a rolling element, where a radial thickness at an axial end surface 5a of the holder 5 is 2.00 mm or more, the resin composition uses polyamide resin as the base resin, and the polyamide resin is a copolyamide containing hexamethylene terephthalamide units and hexamethylene adipamide units as constituent units.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cage for a rolling bearing and a rolling bearing using the cage. [Background technology]

[0002] In rolling bearings, resin cages are widely used as retainers that hold the rolling elements in a rotatable manner. Resin cages are superior to iron cages in terms of self-lubrication, low friction characteristics, and light weight. Aliphatic polyamide resins such as polyamide 6 (PA6) resin, polyamide 66 (PA66) resin, and polyamide 46 (PA46) resin are commonly used as synthetic resins for resin cages, and these are reinforced by incorporating fibrous reinforcing materials such as glass fibers as needed (see Patent Document 1).

[0003] In recent years, there has been a growing demand for higher operating speeds in bearings, particularly in EV applications, requiring resin cages to have high heat resistance. In this context, aromatic polyamide resins, which offer superior heat resistance, are increasingly being considered as an alternative to commonly used aliphatic polyamide resins. For example, polyamide 9T (PA9T) and polyamide 10T (PA10T) have higher glass transition temperatures and melting points compared to aliphatic polyamide resins, and cages using these materials have been proposed (see Patent Documents 2, 3, and 4). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-227120 [Patent Document 2] Japanese Patent Publication No. 2001-317554 [Patent Document 3] Japanese Patent Publication No. 2006-207684 [Patent Document 4] Japanese Patent Publication No. 2016-121735 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] When a rolling bearing incorporating a resin cage is rotated at high speed, the centrifugal force generated by the high-speed rotation acts on the cage, potentially causing it to deform. Deformation of the cage increases friction between the cage and the rolling elements it holds, leading to overheating of the bearing. Furthermore, deformation of the cage can cause contact with the bearing's outer ring, and the resulting frictional heat can melt the resin, potentially causing the rolling bearing to stop rotating. Therefore, resin cages incorporated into rolling bearings used in such high-speed rotation applications are required to resist deformation due to mechanical and / or thermal stresses.

[0006] In contrast, aromatic polyamide resins have high melting points and glass transition temperatures, and excellent high-temperature strength, making them suitable for conditions such as high-speed rotation. However, on the other hand, aromatic polyamide resins tend to have inferior moldability compared to aliphatic polyamide resins due to their high melting point and viscosity. Specifically, due to the high melt viscosity during injection molding and the different volume shrinkage behavior during solidification compared to aliphatic polyamide resins, they are more prone to internal defects (such as cracks and voids) than aliphatic polyamide resins. In particular, when the retainer has a complex shape and is thick-walled, differences in volume shrinkage behavior between the inside and outside are likely to occur, resulting in concerns about the occurrence of internal defects.

[0007] This invention has been made in view of these circumstances, and aims to provide a cage for a rolling bearing that has excellent heat resistance and can achieve good formability even when the cage is thick-walled, and a rolling bearing using the cage. [Means for solving the problem]

[0008] The present invention relates to a rolling bearing cage, which is formed by injection molding a resin composition and has a plurality of pockets for holding rolling elements, wherein the rolling bearing cage has a radial thickness of 2.00 mm or more at the axial end face of the cage, and the resin composition is based on a polyamide resin, and the polyamide resin is a copolymer polyamide containing hexamethylene terephthalamide units and hexamethylene adipamide units as constituent units.

[0009] In this invention, "radial thickness at the axial end face of the retainer (also simply called radial thickness)" refers to half the difference between the inner diameter and outer diameter at the axial end face of the retainer, and if there are multiple such values, the largest of those values ​​is referred to.

[0010] The above-mentioned retainer is characterized by having a radial thickness of 3.00 mm or more at its axial end face.

[0011] In the plan view of the outer diameter surface of the above-mentioned retainer, the diameter of the inscribed circle of the region enclosed by the adjacent pocket and the axial end face is 5.00 mm or more.

[0012] The above polyamide resin is characterized by having a glass transition temperature of 80°C to 110°C and a melting point of 300°C or higher.

[0013] The above resin composition is characterized by containing glass fibers or carbon fibers in an amount of 10% to 50% by mass relative to the entire resin composition.

[0014] The rolling bearing of the present invention is a rolling bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage that holds the rolling elements, wherein the cage is a rolling bearing cage of the present invention.

[0015] The above rolling bearing has a dm·n value of 80 × 10 4 ~300×10 4 It is characterized by being a bearing used in the rotation range. [Effect of the Invention]

[0016] The rolling bearing cage of the present invention has a relatively thick portion with a radial thickness of 2.00 mm or more (particularly 3.00 mm or more), and there is a concern about the generation of internal defects in injection molding. As a polyamide resin which is a base resin, by using a copolymer polyamide containing hexamethylene terephthalamide units and hexamethylene adipamide units as constituent units, it is possible to achieve both the heat resistance of aromatic polyamide resin and the high moldability of aliphatic polyamide resin, resulting in a rolling bearing cage with excellent heat resistance and suppression of the generation of internal defects. Thereby, good moldability can be realized.

[0017] Even when the diameter of the inscribed circle of the region surrounded by adjacent pockets and the axial end face in the plane development view of the outer diameter surface of the cage is 5.00 mm or more, the use of the above polyamide resin can preferably suppress the generation of internal defects.

[0018] Since the above polyamide resin has a melting point of 300 °C or higher, it has higher heat resistance compared to PA66 (melting point: about 260 °C) and PA46 (melting point: about 295 °C), which are generally used as cage materials. Also, it has comparable heat resistance compared to PA9T (melting point: about 305 °C) and PA10T (melting point: about 315 °C). Therefore, for example, the deformation of the cage can be reduced even under high-temperature conditions or high-speed rotation conditions. Furthermore, since the above polyamide resin has a glass transition temperature of 80 °C to 110 °C, for example, even when used under high-speed rotation conditions, the deformation of the cage can be suppressed, and the heat generation due to the sliding friction between the rolling elements and the cage can be reduced.

[0019] Since the resin composition contains 10% to 50% by mass of glass fiber or carbon fiber with respect to the whole resin composition, the rigidity of the cage can be increased, and for example, the deformation of the cage can be made smaller even under high-speed rotation conditions.

[0020] The rolling bearing of the present invention comprises an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage of the present invention that holds these rolling elements, so for example the dm·n value is 80 × 10 4 ~300×10 4 Even when used in high rotational speed ranges, cage deformation can be suppressed, resulting in a bearing with superior durability. [Brief explanation of the drawing]

[0021] [Figure 1] This is an axial cross-sectional view showing an example of a rolling bearing of the present invention. [Figure 2] This is a perspective view showing an example of a cage for a rolling bearing according to the present invention. [Figure 3] This is a diagram illustrating the radial thickness of the retainer. [Figure 4] This is a plan view of the outer diameter surface of the retainer. [Figure 5] This is a partially enlarged perspective view showing another example of a cage for a rolling bearing of the present invention. [Figure 6] This figure shows the measurement locations for evaluating internal defects in the embodiment. [Figure 7] This figure shows the neutral plane and the scope of binarization for evaluating internal defects. [Figure 8] This is an observation image of the holder of Example A. [Figure 9] This is an observation image of the holder of Comparative Example A. [Figure 10] This is an observation image of the holder of Comparative Example B. [Modes for carrying out the invention]

[0022] The rolling bearing cage of the present invention is a resin cage formed by injection molding of a resin composition. This cage is an annular member having a plurality of pockets for holding rolling elements. The resin composition used as the resin material is based on a predetermined polyamide resin, to which a predetermined amount of fibrous reinforcing material (such as glass fiber or carbon fiber) is added as needed.

[0023] The present invention is characterized by using a copolymerized polyamide containing hexamethylene terephthalamide units and hexamethylene adipamide units as constituent units for the retainer polyamide resin. The hexamethylene terephthalamide unit is a constituent unit of PA6T, which is obtained by polymerizing terephthalic acid, a dicarboxylic acid, and 1,6-hexanediamine, a diamine. The hexamethylene adipamide unit is a constituent unit of PA66, which is obtained by polymerizing adipic acid, a dicarboxylic acid, and 1,6-hexanediamine, a diamine.

[0024] In injection-molded resin parts, internal defects such as cracks and voids occur due to differences in shrinkage behavior between the inside and outside caused by the temperature difference between the inside and outside during the cooling and solidification process. For example, aromatic polyamide resins such as PA9T and PA10T exhibit significant differences in shrinkage behavior between the inside and outside, as seen in the PVT diagram, which shows the volume shrinkage behavior during cooling and solidification of the resin, under high pressure differs greatly from that under low pressure. On the other hand, aliphatic polyamide resins tend to exhibit less difference in shrinkage behavior between the inside and outside because their shrinkage behavior is less pressure-dependent. The polyamide resin used in this invention ensures heat resistance with the aromatic polyamide resin PA6T, while the aliphatic polyamide resin PA66 reduces the difference in shrinkage behavior between the inside and outside compared to aromatic polyamide resins, thus making it less prone to internal defects and deformation due to shrinkage.

[0025] As the polyamide resin used in the present invention, for example, a binary copolymer polyamide substantially composed only of PA6T units and PA66 units can be used.

[0026] Furthermore, the polyamide resin may also contain other monomer units. For example, it may be a ternary copolymer polyamide composed of three monomer units including PA6T units and PA66 units, or a quaternary copolymer polyamide composed of four monomer units including PA6T units and PA66 units.

[0027] Other dicarboxylic acid components used in monomer units include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanediic acid, and dodecanediic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid. In addition, diamine components used in other monomer units include aliphatic diamines such as 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11-undecanediamine, and 1,12-dodecanediamine; alicyclic diamines such as cyclohexanediamine; and aromatic diamines such as xylylenediamine. Furthermore, the polyamide resin may be copolymerized with lactams such as caprolactam.

[0028] Examples of ternary copolymer polyamides include copolymer polyamides of PA6T units, PA66 units, and tetramethylene terephthalamide units (the constituent units of PA4T) (PA4T / 6T / 66), and copolymer polyamides of PA6T units, PA66 units, and hexamethylene isophthalamide units (the constituent units of PA6I) (PA6T / 6I / 66).

[0029] The above polyamide resin preferably has a melting point of 300°C or higher, more preferably 300°C to 330°C, and even more preferably 300°C to 320°C. It has a higher melting point and superior heat resistance than PA66 resin and PA46 resin, which are commonly used as retainer materials, making it suitable for high-temperature environments, and for example, for a dm·n value of 80 × 10⁻⁶. 4 Even when used at such high rotational speeds, deformation of the retainer can be prevented. The melting point can be measured using a differential scanning calorimeter (DSC) in an inert gas atmosphere. The endothermic peak temperature (Tm) is measured when the polyamide resin is cooled from a molten state to 25°C at a rate of 20°C / min, and then heated at a rate of 20°C / min.

[0030] The above polyamide resin preferably has a glass transition temperature of 80°C to 110°C, and more preferably 90°C to 110°C. Since its glass transition temperature is higher than that of PA66 resin (glass transition temperature: approximately 60°C) and PA46 resin (glass transition temperature: approximately 78°C), which are commonly used as cage materials, deformation of the cage can be suppressed even when used at high rotation speeds, and heat generation due to sliding friction between the rolling elements and the cage can be reduced. The glass transition temperature can be measured using a differential scanning calorimeter (DSC) in an inert gas atmosphere, by taking the temperature (Tg) at the midpoint of the stepwise endothermic peak that appears when the above polyamide resin is rapidly cooled and then heated at a heating rate of 20°C / min (JIS K7121).

[0031] Various polycondensation methods can be used to produce the polyamide resin used in the present invention, such as melt polymerization, solid-phase polymerization, bulk polymerization, solution polymerization, or combinations thereof.

[0032] The amount of polyamide resin blended is preferably 50% by mass or more, and more preferably 60% to 90% by mass, relative to the total resin composition. The resin composition may also consist solely of polyamide resin (100% by mass).

[0033] The above polyamide resin can be compounded with fibrous reinforcing materials, such as glass fibers or carbon fibers. The amount of fibrous reinforcing material is not particularly limited, but is typically 10% to 50% by mass relative to the total resin composition. By using this range for the fibrous reinforcing material, molding fluidity is ensured and the rigidity of the retainer is increased, so that deformation of the retainer can be reduced even when used at high rotational speeds. Furthermore, if the shape of the retainer is to be forcibly removed during injection molding, or if sufficient strength (tensile strength) of the weld area is to be ensured, the amount of fibrous reinforcing material is preferably 20% to 40% by mass relative to the total resin composition.

[0034] The resin composition in the present invention may contain additives other than the fibrous reinforcing material described above, as necessary, provided that they do not impair the retainer function or injection moldability. Other additives that can be included include, for example, solid lubricants, inorganic fillers, antioxidants, antistatic agents, and release agents.

[0035] The materials constituting the above resin composition can be mixed using a Henschel mixer, ball mixer, ribbon blender, etc., as needed, and then melt-kneaded in a melt extruder such as a twin-screw compounding extruder to obtain molding pellets. Note that side-feeding may be used for adding the filler material when melt-kneading in a twin-screw extruder. The retainer is then molded by injection molding using these molding pellets. During injection molding, the resin temperature should be above the melting point of the polyamide resin, and the mold temperature should be maintained above the glass transition temperature of the polyamide resin.

[0036] The cage for rolling bearings and the rolling bearing of the present invention will be described with reference to Figures 1 and 2. Figure 1 is an axial cross-sectional view of an angular contact ball bearing, which is an example of a rolling bearing of the present invention, and Figure 2 is a perspective view of the cage (machined type) in the rolling bearing of Figure 1.

[0037] As shown in Figure 1, the angular contact ball bearing 1 comprises an inner ring 2, an outer ring 3, a plurality of balls (rolling elements) 4 interposed between the inner ring 2 and the outer ring 3, and a cage 5 that holds these balls 4 at regular intervals in the circumferential direction. The cage 5 is the rolling bearing cage of the present invention described above. The inner ring 2 and outer ring 3 and the balls 4 are in contact with each other at a predetermined angle θ (contact angle) with respect to the radial centerline, and can withstand radial loads and unidirectional axial loads. In Figure 1, the cage 5 is an outer ring guide type, and has an outer ring guide portion on a part of its outer circumferential surface that is guided by the outer ring 3. Note that the guide type of the cage is not limited to the outer ring guide type, but may also be an inner ring guide type. In addition, if necessary, lubricants such as grease are sealed around the balls 4 to provide lubrication.

[0038] The rolling bearing of the present invention is particularly suitable for use under high-temperature and high-speed rotation conditions. The above rolling bearing has a dm·n value of, for example, 80 × 10⁻⁶.4 ~300×10 4 is used in the rotation range of. This dm·n value may be 150×10 4 or more, and may be 200×10 4 or more.

[0039] In FIG. 1, the angular ball bearing 1 uses, as the cage 5, an injection molded body of a resin composition based on a polyamide resin having a high melting point and excellent moldability. Therefore, deformation of the cage can be suppressed even under high-speed rotation conditions. In particular, as shown in the examples described later, since internal defects are suppressed even when the cage is thick-walled, it is considered to be excellent in terms of suppressing breakage of the cage under the load of high-speed rotation and fatigue characteristics. Further, since the above-mentioned polyamide resin is also excellent in self-lubricating properties and low friction characteristics, the amount of heat generated due to friction between the balls 4, the outer ring 3 and the cage 5 can be reduced, and the temperature rise can be suppressed. For this reason, the bearing can be operated for a long time even under high-speed rotation conditions.

[0040] As shown in FIG. 2, the cage 5 is a carded cage, and a plurality of pockets 6 for holding balls are provided at regular intervals in the circumferential direction on an annular cage body. A column portion 7 is formed between the pockets 6 adjacent in the circumferential direction. The cage 5 can be obtained by forming the pocket portion by injection molding with a mold having a slide core using the above resin composition, or by processing the pocket portion by cutting after forming a blank.

[0041] In the cage 5, the direction parallel to the central axis O is referred to as the axial direction, the direction orthogonal to the central axis O in a plan view seen from the axial direction is referred to as the radial direction, and the direction that circulates around the central axis O in the plan view is referred to as the circumferential direction.

[0042] In Figure 2, the axial end face 5a of the retainer 5 is formed as an annular flat surface and has a certain thickness (constant in Figure 2) in the radial direction of the retainer 5. The present invention targets retainers with a radial thickness of 2.00 mm or more. The radial thickness of the retainer 5 may be 3.00 mm or more, or 5.00 mm or more. As this radial thickness increases, internal defects tend to occur more easily in aromatic polyamide resins such as PA9T and PA10T, so the retainer of the present invention is particularly suitable for thick-walled retainers. The radial thickness of the retainer 5 may be, for example, 20.00 mm or less, or 15.00 mm or less.

[0043] The radial thickness of the retainer will be further explained with reference to Figure 3. Figure 3(a) is a partial plan view of the axial end face of the retainer, and Figure 3(b) is a cross-sectional view of the same face along line AA. The radial thickness d at the axial end face 5a of the retainer 5 can be determined as half the difference between the inner diameter dimension r and the outer diameter dimension R of the axial end face 5a at any circumferential position. The inner and outer diameter dimensions at the axial end face of the retainer can be measured using a ruler or caliper. In the retainer 5 shown in Figure 3, a rib portion 7a is provided on the inner diameter side of the column portion 7, but in this case, the rib portion 7a is not formed extending to the axial end face 5a, and the thickness of the rib portion 7a is not included in the radial thickness d of the retainer 5.

[0044] Here, depending on the shape of the axial end face of the retainer, the radial thickness d may not be constant. For example, as shown in Figure 3(b), a step 5d, such as a material removal, may be provided on the outer or inner diameter side of one of the axial end faces (5a') of the retainer 5. In such cases, half the difference between the inner diameter dimension r and the outer diameter dimension R can take on multiple values, and the largest of these values ​​is taken as the radial thickness d. For example, in the case of Figure 3(b), the dimension on the axial end face 5a side becomes the radial thickness d. In this way, the inner diameter dimension and outer diameter dimension can be measured at the points where the inner diameter shape and outer diameter shape of the axial end face change according to the shape of the retainer, and the radial thickness d can be determined based on these measurements.

[0045] Next, Figure 4 shows a plan view of the outer diameter surface of the retainer. Figure 4 is a diagram showing one unit of the repeating structure of the outer diameter surface. In the retainer 5, half-portions 6, 6 are arranged on both sides of the central column 7.

[0046] When a retainer is injection molded, the cooling and solidification rate of the molten resin differs significantly between the portion near the surface of the cavity that is in contact with the molding die and the portion further away from the surface. In a retainer, the portion near the base of the column is particularly likely to be the furthest from the cavity surface, and is therefore prone to internal defects. In the present invention, by using the polyamide resin described above, internal defects in such portions can be effectively suppressed.

[0047] Specifically, even in a retainer where the diameter φ of the inscribed circle 8 in the region enclosed by adjacent pockets 6, 6 and the axial end face 5a is 3.00 mm or more, internal defects in that portion can be suitably suppressed. The diameter φ of the inscribed circle 8 may be 5.00 mm or more. On the other hand, the diameter φ of the inscribed circle 8 may be, for example, 15.00 mm or less, or 10.00 mm or less. When setting the inscribed circle 8, the shape of the pocket 6 in the plan view is set as a circle without considering shapes such as the material removal 7b formed around the pocket 6. The diameter φ of the inscribed circle 8 can be calculated from the following formula (1) when the pockets 6 are arranged equally and the center of the pocket is in the center of the width (axial length) L of the retainer 5.

[0048]

number

[0049] In equation (1) above, W represents the unit width of the retainer (outer circumference length / number of pockets), L represents the width of the retainer, and D represents the pocket diameter.

[0050] In the cage for rolling bearings of the present invention, the width L of the cage is, for example, 5.00 mm to 40.00 mm, preferably 10.00 mm to 35.00 mm. Furthermore, the ratio of the width L to the thickness d (L / d) is preferably 3.00 to 6.00, as this makes it easier to reduce the occurrence of voids and the like.

[0051] Furthermore, the pocket diameter D and unit width W (circumferential length / number of pockets) in the retainer are not particularly limited and can be set as appropriate. For example, the pocket diameter D is 5.00 mm to 40.00 mm, preferably 10.00 mm to 35.00 mm. For example, the unit width W is 10.00 mm to 40.00 mm, preferably 10.00 mm to 30.00 mm.

[0052] In Figures 1 and 2, an angular contact ball bearing is used as an example of a rolling bearing according to the present invention. However, the bearing types to which the present invention can be applied are not limited to this, and it can also be applied to other ball bearings, tapered roller bearings, cylindrical roller bearings, self-aligning roller bearings, needle roller bearings, and the like.

[0053] As another example of a cage for rolling bearings of the present invention, a crown-type cage will be described with reference to Figure 5. Figure 5 is a partially enlarged perspective view of a crown-type cage obtained by injection molding the above-described resin composition. As shown in Figure 5, the cage 9 has a pair of opposing retaining claws 10 formed on the upper surface of an annular cage body at a constant pitch in the circumferential direction, and each of the opposing retaining claws 10 is curved in a direction toward each other, and pockets 11 for holding balls as rolling elements are formed between the retaining claws 10. In addition, a flat portion 12 is formed between the back surfaces of mutually adjacent retaining claws 10 in adjacent pockets 11, which serves as a reference surface for the rise of the retaining claws 10.

[0054] In the case of a crown-type retainer, the radial thickness of the axial end face 9a opposite to the retaining claw 10 is 2.00 mm or more. This radial thickness can be determined in the same way as explained in Figure 3. The same considerations apply to the inscribed circle. Furthermore, this method can also be applied to other types of retainers.

[0055] The rolling bearing cage of the present invention can suppress internal defects even in relatively thick cages where aromatic polyamide resins are prone to internal defects, by using a polyamide resin copolymerized with a specific aromatic polyamide resin and an aliphatic polyamide resin. Furthermore, it can reduce internal defects compared to conventionally widely used aliphatic polyamide resins.

[0056] Conventionally, to suppress internal defects and deformation caused by shrinkage behavior, methods such as creating a thickness reduction in thicker sections are employed, and mold structures that minimize the temperature difference between the inside and outside are sometimes used. However, depending on the shape of the retainer, it may be difficult to create a thickness reduction, or the thickness of the thickness reduction may need to be increased. The present invention is effective in addressing internal defects and deformation without requiring such measures. [Examples]

[0057] The present invention will be further described below with reference to examples, but the present invention is not limited thereto.

[0058] Retainers of various dimensions were fabricated using various resin materials, and the occurrence of internal defects (cracks and voids) was investigated. The resin compositions used in the examples and comparative examples are shown below. Each resin composition consisted of 100% by mass of polyamide resin. Example A: PA6T / 66 Comparative example A: PA10T Comparative example B: PA66 Comparative example C: PA9T Comparative example D: PA6T / 6I

[0059] First, using PA6T / 66 (Example A) and PA10T (Comparative Example A), the cages No. 1 to 10 shown in Table 1 were manufactured by injection molding. The cage shape was a machined mold as shown in Figure 2. For each manufactured cage, the radial thickness d and the diameter of the inscribed circle φ were measured. The radial thickness d was determined as half the difference between the inner and outer diameters of the axial end face. The diameter of the inscribed circle φ was determined using the above formula (1). The ratio of width L to thickness d (L / d) was in the range of 3.00 to 6.00 for cages No. 1 to 8, and less than 3.00 for cages No. 9 to 10. The results are shown in Table 1.

[0060] For each retainer, internal defects were evaluated based on CT cross-sectional images of the neutral plane of the thickest wall section where defects are most likely to occur. Figure 6 shows the measurement area (region B) of internal defects in retainer 13, and Figures 8 and 9 show CT cross-sectional images of Example A and Comparative Example A of No. 7. Cracks were evaluated based on the presence or absence of cracks based on the CT cross-sectional images (3: no cracks, 2: cracks present). Voids were evaluated by calculating the defect area ratio based on the CT cross-sectional images (3: no defects, 2: defect area ratio less than 10%, 1: defect area ratio 10% or more). The defect area ratio was calculated by extracting CT cross-sectional images of the neutral plane (see Figure 7(a)) for thickness d where voids and cracks are likely to form within the observation range shown in Figure 6, and binarizing the range where voids are observed as shown in Figure 7(b). The results are shown in Table 1.

[0061] [Table 1]

[0062] As shown in Table 1, in Example A using PA6T / 66, no cracks occurred, and voids were only slightly observed in extremely thick materials with a thickness d of 10.00 mm or more, indicating a favorable result. As shown in Figure 8, no cracks or voids were observed in retainer No. 7.

[0063] In contrast, in comparative example A using PA10T, although the results were good when the thickness d was thin, a tendency for internal defects such as cracks and voids to occur was observed when the radial thickness d was 3.00 mm or more. Furthermore, even when the radial thickness d was the same, differences in void occurrence were observed. In the case of a complex-shaped retainer, the diameter φ of the inscribed circle is suitable for representing the wall thickness, and it was confirmed that the diameter φ of the inscribed circle in the planar unfolded view of the outer diameter surface of the retainer also affects the amount of voids.

[0064] Next, retainers No. 4, 7, and 10 were fabricated by injection molding using PA66 (Comparative Example B), PA9T (Comparative Example C), and PA6T / 6I (Comparative Example D). The retainer shape was a machined mold as shown in Figure 2. Internal defects were evaluated for these retainers in the same manner as described above. Figure 10 shows a CT cross-sectional image of Comparative Example B of No. 7. The results are shown in Table 2.

[0065] [High-speed endurance test] High-speed durability tests were conducted using cage No. 4 in Example A and Comparative Examples A-D. Using angular contact ball bearings, a dm·n value of 80 × 10⁻¹ was achieved. 4 dm·n value 160 × 10 4 dm·n value 240 × 10 4 dm·n value 280 × 10 4 Each was subjected to a 100-hour durability test. Comparative tests were conducted using angular contact ball bearings that incorporated each cage of Example A and Comparative Examples A-D, filled with grease as a lubricant, and sealed with non-contact seals on both sides. After the test, a rating of "3" was given if there was no damage to the cage, a rating of "2" if vibration occurred or the cage was damaged, and a rating of "1" if the cage melted, the maximum temperature limit was reached, or the motor output was excessive. The results are shown in Table 2.

[0066] [Table 2]

[0067] As shown in Table 2, aromatic polyamide resins such as PA10T and PA9T (Comparative Examples A and C) exhibited high melting points and glass transition temperatures, and showed high durability in high-speed durability tests. However, cages made from these resins had internal defects such as cracks and voids, which may lead to cage fracture or reduced fatigue properties when stress increases due to changes in operating conditions (lubrication conditions). In the case of the aliphatic polyamide resin PA66 (Comparative Example B), voids occurred, but no cracks occurred. However, because PA66 has a low melting point and glass transition temperature, its durability decreased under higher rotational conditions. Furthermore, cracks and other defects were also observed in another aromatic polyamide resin, PA6T / 6I (Comparative Example D), which is a PA6T-based material.

[0068] In contrast, Example A, which used PA6T / 66, showed reduced internal defects such as cracks and voids, as well as higher melting and glass transition temperatures compared to PA66, and demonstrated sufficient durability even under high-speed rotation test conditions.

[0069] In this way, by using a predetermined polyamide resin obtained by copolymerizing aromatic polyamide resin and aliphatic polyamide resin, it is possible to manufacture resin retainers that combine the high moldability of aliphatic polyamide resin with the heat resistance of aromatic polyamide resin. As a result, even in the case of thick-walled retainers, for example, internal defects and deformation of the retainer can be suppressed without creating material loss, and internal defects and deformation of the retainer can be addressed without processing complex mold shapes. [Industrial applicability]

[0070] The cage for rolling bearings of the present invention offers excellent heat resistance and good formability even when the cage is thick-walled, and in particular can suppress the occurrence of internal defects such as cracks and voids. Therefore, it can withstand high-temperature atmospheres (e.g., temperatures above 80°C) and high-speed rotation conditions (e.g., when the dm·n value is 80 × 10⁻⁶). 4 It is suitable for use in the above applications and can be used as a cage for various rolling bearings used in automobiles, motors, machine tools, etc. [Explanation of Symbols]

[0071] 1. Angular contact ball bearing (rolling bearing) 2 Inner ring 3 Outer ring 4 balls 5 Cage 6 pockets 7 Pillar part 8. Inscribed Circle 8 retaining claws 9 Cage 10 retaining claws 11 pockets 12 Flat area 13 Cage

Claims

1. A cage for a rolling bearing, formed by injection molding of a resin composition and having a plurality of pockets for holding rolling elements, The aforementioned rolling bearing cage has a radial thickness of 3.00 mm or more at its axial end face, and in a plan view of the outer diameter surface of the cage, the diameter of the inscribed circle of the region enclosed by adjacent pockets and the axial end face is 5.00 mm or more. The aforementioned resin composition is a polyamide resin, and the polyamide resin is a copolymer polyamide containing hexamethylene terephthalamide units and hexamethylene adipamide units as constituent units, characterized in that it is a cage for rolling bearings.

2. The cage for a rolling bearing according to claim 1, characterized in that the polyamide resin has a glass transition temperature of 80°C to 110°C and a melting point of 300°C or higher.

3. The cage for a rolling bearing according to claim 1 or 2, characterized in that the resin composition contains glass fibers or carbon fibers in an amount of 10% to 50% by mass relative to the entire resin composition.

4. A rolling bearing comprising an inner ring and an outer ring, a plurality of rolling elements interposed between the inner and outer rings, and a cage that holds the rolling elements, A rolling bearing characterized in that the cage is a rolling bearing cage according to any one of claims 1 to 3.

5. The aforementioned rolling bearing has a dm·n value of 80 × 10 ４ ~300 x 10 ４ The rolling bearing according to claim 4, characterized in that it is a bearing used in the rotation range.

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