Jade Axis

Abstract

To provide a ball bearing which can suppress the leakage of grease at low torque even if a sealing amount of the grease into the ball bearing is increased while being simple in a manufacturing process.SOLUTION: A ball bearing 1 comprises: an inner ring 2 having an inner ring raceway groove 2a at an external periphery; an outer ring 3 having an outer ring raceway groove 3a at an internal periphery; a plurality of balls 4 assembled between the inner ring raceway groove 2a and the outer ring raceway groove 3a; a cage 6 for holding the plurality of balls 4; and a seal member 5 fixed to an outer ring seal groove 3b formed at the outer ring 3 at one end part, and contacting with an inner ring seal groove 2b formed at the inner ring 2 at the other end part. Grease is sealed into the ball bearing 1, and the ball bearing 1 has an oil repellent coating layer on only a surface of a shoulder part 2c arranged between the inner ring raceway groove 2a and the inner ring seal groove 2b out of an outside-diameter face of the inner ring 2, and an inside-diameter face 6c of the cage opposing the outside-diameter face of the inner ring 2 out of the cage 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ball bearing, and more particularly to a ball bearing used in home appliances, industrial equipment, automotive electrical components, etc., that has a function to prevent grease leakage. [Background technology]

[0002] Ball bearings generally consist of an inner ring, an outer ring, balls (rolling elements), and a cage. A seal is provided at the open end to prevent the intrusion of foreign matter from the outside and to prevent leakage of the grease sealed within the bearing space. In sealed ball bearings, grease can leak if it adheres to the seal grooves at both axial ends of the inner or outer ring (the bearing ring). Grease leakage can be prevented by increasing the contact force between the seal lip of the seal and the bearing ring. However, this also increases frictional resistance, which is known to cause increased torque and heat generation. Various technologies have been proposed to reduce frictional resistance while maintaining sealing performance.

[0003] In conventional sealed ball bearings, when the bearing rotates, grease adhering to the balls is scraped off by the cage due to rotation and adheres to the cage. When grease adhering to the inner diameter side of the cage accumulates, it adheres to the surface of the shoulder located between the inner ring raceway groove and the inner ring seal groove on the outer diameter surface of the inner ring. As the bearing rotates, the amount of grease adhering to the shoulder surface of the inner ring increases, and when it collides with the pocket in the cage, grease can adhere from the seal groove of the inner ring to the pocket, causing a grease leak.

[0004] Patent Documents 1 and 2 describe bearings in which the shape of the cage is changed from the conventional shape to suppress grease leakage. In Patent Documents 1 and 2, recesses are provided in the pockets of the cage, which increases the amount of grease that can adhere to the cage and makes it easier for the grease to move to the outer diameter side of the cage, reducing the amount of grease that can remain on the inner diameter side. This prevents grease from adhering to the surface of the shoulder of the inner ring, thereby suppressing grease leakage.

[0005] Furthermore, Patent Document 3 proposes a method for suppressing grease leakage by surface processing of the seal contact area. In Patent Document 3, in a sealing device in which a seal lip slides in a seal groove, shot peening is performed on the sliding contact surface of the seal groove where the seal lip slides. With this configuration, the bearing is fluid-sealed to ensure sealing performance, and the seal lip does not stick, resulting in stable rotational torque. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5465297 [Patent Document 2] Patent No. 5507837 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-69404 Summary of the Invention [Problem to be solved by the invention]

[0007] As automotive electrical accessories become smaller, the rotation speed of bearings is also increasing. Furthermore, the bearings installed in electric vertical take-off and landing aircraft, which have been developed in recent years, are also expected to operate at high speeds. When bearings are used at high speeds, good grease lubrication and low torque are required. Increasing the amount of grease packed in ensures lubrication, but the larger the amount packed in, the more grease adheres to the surface of the shoulder of the inner ring, which can lead to grease leakage.

[0008] The cages described in Patent Documents 1 and 2 actively utilize the centrifugal force acting on the cage to reduce torque and prevent grease leakage without increasing the contact force between the seal lip and the bearing ring. Bearings equipped with these cages are particularly effective in preventing grease leakage under high-speed rotation. However, bearings are not limited to high-speed rotation; they are also used under low-speed rotation, and the rotational speed of the bearing fluctuates. Therefore, if a large amount of grease is packed into the bearing and it is often used at low speeds, the bearing may not be able to perform to its full potential. Therefore, there is a demand for bearings that are even more effective at preventing grease leakage, even when a large amount of grease is packed into the bearing.

[0009] In Patent Document 3, even if the fluid seal has a sealing effect, the contact area between the seal lip and the seal groove is reduced by shot peening, and therefore, if a large amount of grease is filled, it is expected that the effect of suppressing grease leakage will be insufficient.

[0010] Furthermore, compared to conventional cages, the cages described in Patent Documents 1 and 2 require additional processing to create recesses on the inner surface of the pocket, and the bearing described in Patent Document 3 requires shot peening, a type of blasting, on the surface of the seal groove in the inner ring. Therefore, it is preferable that grease leakage can be suppressed even with a cage manufactured using a simpler manufacturing process. In particular, there is a demand for bearings that can improve sealing performance and reduce torque without significantly changing the shape of existing products.

[0011] The present invention has been made to address such problems, and aims to provide a ball bearing that can be manufactured simply and that can suppress grease leakage at low torque even when the amount of grease sealed inside the ball bearing is increased. [Means for solving the problem]

[0012] The ball bearing of the present invention comprises an inner ring having an inner ring raceway groove on its outer circumference, an outer ring having an outer ring raceway groove on its inner circumference, a plurality of balls assembled between the inner ring raceway groove and the outer ring raceway groove, a retainer that holds the plurality of balls, and a seal member having one end fixed to an outer ring seal groove provided in the outer ring and the other end contacting an inner ring seal groove provided in the inner ring, and is characterized in that grease is sealed inside the bearing, and an oil-repellent coating layer is formed only on the surface of a shoulder portion of the outer diameter surface of the inner ring that is positioned between the inner ring raceway groove and the inner ring seal groove, and on the inner diameter surface of the retainer that faces the outer diameter surface of the inner ring.

[0013] The ball bearing further comprises the oil-repellent coating layer on an abutment surface of the inner diameter surface of the outer ring that is abutted against in the axial direction by the seal member.

[0014] The ball bearing is characterized in that the oil-repellent coating layer is not provided on the surface of the seal member.

[0015] The oil-repellent coating layer is characterized by being a film made of a fluorine-based coating agent.

[0016] The retainer is characterized in that it is a crown-shaped ball bearing retainer consisting of an annular body having a plurality of pocket portions, one of which is open on one side to hold the balls, and a connecting plate portion that connects adjacent pocket portions.

[0017] The ball bearing is characterized in that it is mounted on an electric vertical take-off and landing aircraft that has multiple drive units each having a rotor and a motor that rotates the rotor, and that flies by rotating the rotor, and is a bearing that supports the rotating shaft in the drive unit. [Effects of the Invention]

[0018] The ball bearing of the present invention includes an inner ring, an outer ring, balls, a cage, and a seal member. The bearing is filled with grease, and the outer diameter surface of the cage is coated only on the shoulder surface of the inner ring, which is located between the inner ring raceway groove and the inner ring seal groove, and on the inner diameter surface of the cage, which faces the outer diameter surface of the inner ring. Therefore, the grease has a higher affinity for the shoulder surface of the outer ring, which is located between the outer ring raceway groove and the outer ring seal groove and the outer diameter surface of the cage, which are relatively less oil-repellent, than the shoulder surface of the inner ring and the inner diameter surface of the cage, which are highly oil-repellent. Therefore, the grease is less likely to accumulate on the inner ring side. This facilitates migration of the grease from the inner ring side to the outer ring side of the bearing, even when the bearing rotates at low speeds and centrifugal force is relatively weak. As a result, grease is less likely to adhere to the seal groove of the inner ring, where grease leakage is likely to occur. Therefore, even if the amount of grease packed inside the ball bearing is increased, grease leakage can be suppressed at low torque without increasing the contact force between the seal lip of the seal member and the raceway. Furthermore, predetermined locations within the bearing can be made oil-repellent simply by forming an oil-repellent coating layer, without the need to process the cage into a special shape, further simplifying the manufacturing process.

[0019] Furthermore, if the grease migrates to the outer ring side and is more likely to accumulate, there is the possibility that base oil may leak from the outer diameter side (fixed part side) of the sealing member. However, the ball bearing further has an oil-repellent coating layer on the abutment surface of the inner diameter surface of the outer ring that abuts against the sealing member from the axial direction, thereby preventing base oil leakage from the outer diameter side of the sealing member.

[0020] Because the ball bearing does not have an oil-repellent coating layer on the surface of the sealing member, the number of parts on which the oil-repellent coating layer must be formed is reduced, further simplifying the manufacturing process. In addition, the amount of coating agent used to form the oil-repellent coating layer can be reduced, which also reduces raw material costs.

[0021] The oil-repellent coating layer is a film made of a fluorine-based coating agent, and therefore has an excellent effect of suppressing grease leakage.

[0022] The cage is a crown-shaped ball bearing cage made of an annular body having multiple pockets with openings on one side to hold the balls and connecting plates that connect adjacent pockets, so that the amount of grease scraped off by the cage as the balls rotate and accumulated on the cage is reduced, and the movement of grease from the inner ring to the outer ring is promoted, resulting in an even more effective suppression of grease leakage.

[0023] Furthermore, the ball bearing of the present invention has low torque and can suppress grease leakage even when the amount of grease sealed inside the bearing is increased, making it suitable for use in electric vertical take-off and landing aircraft, which are expected to be used at high speeds. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view of a first embodiment of a ball bearing according to the present invention. [Figure 2] FIG. 10 is a perspective cross-sectional view of a cage with an oil-repellent coating. [Figure 3] FIG. 1 is a perspective cross-sectional view of an inner ring with an oil-repellent coating. [Figure 4] FIG. 1 is a perspective cross-sectional view of an outer ring with an oil-repellent coating. [Figure 5] FIG. 3 is a cross-sectional view of a second embodiment of a ball bearing according to the present invention. [Figure 6] 1 is a perspective view of an electric vertical take-off and landing aircraft in which a ball bearing according to the present invention is mounted. [Figure 7] FIG. 1 is a partial cross-sectional view of a motor in a drive unit of an electric vertical take-off and landing aircraft. DETAILED DESCRIPTION OF THE INVENTION

[0025] (First embodiment) A first embodiment of a ball bearing according to the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 is an axial cross-sectional view of the upper side of a deep groove ball bearing filled with grease, as viewed vertically. As shown in FIG. 1, ball bearing 1 comprises an inner ring 2 having an inner ring raceway groove 2a on its outer periphery and an outer ring 3 having an outer ring raceway groove 3a on its inner periphery, which are arranged concentrically. A plurality of balls 4 are fitted between the inner ring raceway groove 2a and the outer ring raceway groove 3a. These balls 4 are held at equal intervals in the circumferential direction by a cage 6. Ball bearing 1 is provided with seal members 5 at openings at both axial ends of the inner and outer rings. Ball bearing 1 is lubricated by grease (not shown) sealed in the bearing space defined by the inner ring 2, outer ring 3, and seal member 5. The grease is sealed around at least the balls 4.

[0026] FIG. 2 is a perspective cross-sectional view of the cage. As shown in FIG. 2, the cage 6 is a crown-shaped ball bearing cage consisting of an annular body having a plurality of pockets 6a, each of which is partially open on one side to hold the balls, and a connecting plate 6b connecting adjacent pockets 6a. As a result, compared to a typical stamped cage, the rotation of the balls scrapes off grease, reducing the amount of grease accumulated on the cage and promoting the movement of grease from the inner ring to the outer ring. As a result, it is effective in suppressing grease leakage. The cage 6 is made of resin. Note that the cage is not limited to being made of resin, but may also be made of metal. The shape of the cage is not limited to the above-mentioned crown-shaped ball bearing cage, but may also be a stamped cage, etc.

[0027] Fig. 3 is a perspective cross-sectional view of the inner ring. As shown in Fig. 3, the inner ring 2 has, on its outer diameter surface, an inner ring raceway groove 2a with which the balls contact, an inner ring seal groove 2b with which one end of the seal member contacts, and a shoulder 2c located between the inner ring raceway groove 2a and the inner ring seal groove 2b. The inner ring seal groove 2b is provided at both axial ends of the outer diameter surface of the inner ring 2.

[0028] Figure 4 is a perspective cross-sectional view of the outer ring. As shown in Figure 4, the outer ring 3 has, on its inner diameter surface, an outer ring raceway groove 3a with which the balls come into contact, an outer ring seal groove 3b to which one end (fixed portion) of the seal member is fixed, and a shoulder 3c located between the outer ring raceway groove 3a and the outer ring seal groove 3b. The outer ring seal groove 3b is provided on both axial ends of the inner diameter surface of the outer ring 3.

[0029] As shown in Fig. 1, the seal member 5 is fixed by having its fixed portion fitted into the outer ring seal groove 3b, and its other end contacts the inner ring seal groove 2b. The fixed portion of the seal member 5 comes into close contact with an abutment surface 3d, which is part of the inner diameter surface of the outer ring 3 and abuts against it in the axial direction, over the entire circumference, preventing grease from leaking out. In Fig. 1, the abutment surface 3d is the side wall surface on the axially inner side of the seal groove 3b.

[0030] The sealing member 5 is composed of an elastic member made of rubber or synthetic resin and a metal plate embedded in the elastic member. The sealing member 5 may be a composite of a rubber molded body and a plastic plate or ceramic plate, or may be a metal or rubber molded body alone. From the viewpoints of durability and grease sealing performance, a composite of a rubber molded body and a metal plate is preferred.

[0031] Next, the locations where the oil-repellent coating layer is formed will be described. The ball bearing of the present invention is characterized by having an oil-repellent coating layer only on (1) the surface of the shoulder portion of the outer diameter surface of the inner ring, which is located between the inner ring raceway groove and the inner ring seal groove, and (2) the inner diameter surface of the cage that faces the outer diameter surface of the inner ring. In the ball bearing 1 of the first embodiment, in addition to the surface of the shoulder portion 2c of the inner ring 2 and the inner diameter surface 6c of the cage 6, the oil-repellent coating layer is also formed on the abutment surface 3d of the inner diameter surface of the outer ring 3 that abuts against the seal member 5 in the axial direction (see FIGS. 1 to 4).

[0032] In the first embodiment, by forming an oil-repellent coating layer on the above-mentioned locations, grease has a higher affinity for the surface of the shoulder 3c of the outer ring 3 and the outer diameter surface of the cage 6, which have relatively low oil repellency, compared to the surface of the shoulder 2c of the inner ring 2, the inner diameter surface 6c of the cage 6, and the abutment surface 3d, which have relatively high oil repellency. This makes it difficult for grease to accumulate on the inner ring side (see Figures 1 to 4). As a result, even when the bearing rotates at a low speed and the centrifugal force is relatively weak, the grease moves from the inner ring side to the outer ring side of the ball bearing 1 due to surface tension caused by the surface energy of the substrate. As a result, grease is less likely to adhere to the seal groove of the inner ring, where grease leakage is likely to occur, and grease leakage can be suppressed even when a large amount of grease is packed in. Furthermore, by forming an oil-repellent coating layer on the abutment surface 3d, grease leakage from the seal groove of the outer ring can also be suppressed. Furthermore, by simply forming an oil-repellent coating layer, it is possible to easily make specific locations in a bearing oil-repellent without significantly modifying the shape of existing parts, further simplifying the manufacturing process.

[0033] In Figure 1, the ball bearing 1 does not have an oil-repellent coating layer on the surface of the shoulder 3c of the outer ring 3 or on the outer diameter surface of the cage 6. For example, if an oil-repellent coating layer were formed on these surfaces, it would be more likely for grease to move into the seal groove 2b of the inner ring 2 when the bearing rotates, so from the perspective of preventing grease leakage, an oil-repellent coating layer is not formed on these surfaces.

[0034] The ball bearing of the present invention may also have an oil-repellent coating layer on other surfaces of the bearing members. For example, the oil-repellent coating layer may be on the seal groove (including the abutment surface) of the outer ring or on the surface of the seal member. For example, by forming an oil-repellent coating layer on the surface of the seal groove of the outer ring and on the surface of the fixing part of the seal member that is fixed to the seal groove, the base oil can be made to bead and base oil leakage can be prevented, even if there is edge residue on the outer ring side.

[0035] On the other hand, as shown in Figure 1, a configuration can be adopted in which no oil-repellent coating layer is formed on the surface of the sealing member 5. This reduces the number of components on which the oil-repellent coating layer is formed, further simplifying the manufacturing process. It also allows for a significant reduction in the amount of coating agent used to form the oil-repellent coating layer. In particular, if the coating agent is a fluorine-based coating agent, it is relatively expensive, so reducing the amount used also reduces raw material costs.

[0036] The oil-repellent coating layer used in the present invention is, for example, a film made of a fluorine-based coating agent. The coating is formed by applying the fluorine-based coating agent to the areas where oil repellency is desired and then drying. In the case of the first embodiment, masking tape is applied to areas other than the surface of the shoulder of the inner ring, the inner diameter surface of the cage, and the abutment surface of the outer ring, and then the fluorine-based coating agent is applied by spray coating and allowed to dry at room temperature for a predetermined time (for example, about a few seconds), thereby forming the oil-repellent coating layer.

[0037] The oil-repellent coating layer adheres to the underlying surfaces of the inner ring, outer ring, and cage through intermolecular forces. This eliminates the need for a high-temperature heating process to form chemical bonds, and the substrate can be easily made oil-repellent by simply drying naturally, simplifying the manufacturing process. In addition, the fluorine-based coating agent is applied with an adhesive coating and adheres to the substrate, so it does not scatter from the substrate even when the bearing rotates.

[0038] Fluorine-based coating agents are effective at reducing surface energy. Therefore, the surface energy of areas where an oil-repellent coating layer is formed by a fluorine-based coating agent is significantly reduced, resulting in a significant difference in grease wettability between areas where an oil-repellent coating layer is formed and areas where it is not. As a result, grease can more easily move from areas with low surface energy to areas with higher surface energy inside the bearing.

[0039] Furthermore, since fluorine-based coating agents have a chemically stable structure, they do not chemically react with grease and affect lubrication. Examples of fluorine-based coating agents that can be used include fully fluorinated resins, partially fluorinated resins, and fluorinated resin copolymers.

[0040] Furthermore, the fluorine-based coating agent preferably contains a fluororesin having a perfluoroalkyl group. Since all of the hydrogen atoms in the alkyl group of the perfluoroalkyl group are replaced with fluorine atoms, the perfluoroalkyl group significantly contributes to reducing the surface energy of the coating film. The number of carbon atoms in the perfluoroalkyl group contained in the fluororesin is preferably within the range of 1 to 6. By setting the carbon number within the range of 1 to 6, the coating agent has excellent environmental compatibility and can be applied to a variety of applications. Here, examples of fluorine-based oil-repellent coating agents that can be suitably used include Asahi Guard (manufactured by AGC Corporation), Surflon (manufactured by AGC Seimi Chemical Co., Ltd.), METAX (manufactured by Kanto Kasei Co., Ltd.), and Rain Guard (manufactured by Lion Corporation).

[0041] The oil-repellent coating layer is not limited to a fluorine-based coating agent, and may be formed using a silicone-based coating agent, etc. Examples of silicone-based coating agents that can be used include dimethylsiloxane and methylphenylsiloxane.

[0042] As a method for applying various coating agents, various methods can be selected, such as spray coating, dip coating, jet dispenser coating, and hand coating. From the viewpoint of ease of application and uniformity of coating film thickness, spray coating and dip coating are preferred. The drying method is not particularly limited, and room temperature drying or heat drying can be used. As a means for heat drying, for example, a dryer, a hot air oven, a high-frequency induction heating oven, an infrared oven, etc. can be used.

[0043] The thickness of the oil-repellent coating layer can be freely selected, but is preferably in the range of 0.05 μm to 10 μm. By keeping the thickness within this range, both a uniform film thickness and oil repellency can be achieved. From the viewpoint of cost reduction, the thickness of the oil-repellent coating layer is more preferably in the range of 0.05 μm to 1 μm. Furthermore, in order to improve the adhesion of the oil-repellent coating layer to the substrate, pretreatment such as providing a primer layer before applying the oil-repellent coating layer may be performed.

[0044] The ball bearing of the present invention is lubricated with grease. The grease is sealed in the bearing interior space and is present on the raceway surfaces, etc., to provide lubrication. The base oil constituting the grease can be any oil typically used in ball bearings, without any particular limitations. Examples include mineral oils such as paraffinic mineral oil and naphthenic mineral oil; hydrocarbon synthetic oils such as polybutene oil, poly-α-olefin oil, alkylbenzene oil, and alkylnaphthalene oil; and non-hydrocarbon synthetic oils such as natural fats and oils, polyol ester oil, phosphate ester oil, diester oil, polyglycol oil, silicone oil, polyphenyl ether oil, alkyl diphenyl ether oil, and fluorinated oil. These lubricating oils may be used alone or in combination of two or more.

[0045] Examples of thickeners that make up the grease include metal soap-based thickeners such as aluminum soap, lithium soap, sodium soap, lithium complex soap, calcium complex soap, and aluminum complex soap, urea-based compounds such as diurea compounds and polyurea compounds, and fluororesin powders such as PTFE resin. These thickeners may be used alone or in combination of two or more.

[0046] Furthermore, known additives can be added to the grease as needed, such as extreme pressure agents such as organic zinc compounds and organic molybdenum compounds, antioxidants such as amine-based, phenol-based, and sulfur-based compounds, wear inhibitors such as sulfur-based and phosphorus-based compounds, rust inhibitors such as polyhydric alcohol esters, viscosity index improvers such as polymethacrylate and polystyrene, solid lubricants such as molybdenum disulfide and graphite, and oiliness agents such as esters and alcohols.

[0047] The amount of grease to be filled is not particularly limited as long as it is within a range that ensures the desired lubrication characteristics, but for example, it is 65% to 100% (volume ratio) of the static space volume in the bearing interior, and preferably 80% to 100% of the static space volume. The ball bearing of the present invention can suppress grease leakage even when a large amount of grease is filled. Here, the "static space volume" refers to the volume of the space in which the grease can remain stationary even when the rolling elements and cage rotate (the space through which the rolling elements and cage do not pass when the bearing rotates).

[0048] (Second embodiment) A ball bearing according to a second embodiment of the present invention will be described with reference to Fig. 5. Note that the same components as those in the first embodiment described with reference to Fig. 1 are given the same reference numerals, and detailed description thereof will be omitted.

[0049] As shown in Figure 5, ball bearing 11 differs from the ball bearing of the first embodiment in that the shape of cage 16 is a stamped metal cage. Also, the ball bearing of the second embodiment differs in that the oil-repellent coating layer is formed in two locations: on the surface of shoulder portion 2c of inner ring 2 and on inner diameter surface 16c of cage 16. Ball bearing 11 has higher strength against vibration and acceleration than ball bearing 1 because balls 4 are held in cage 16 that is riveted.

[0050] In the second embodiment, the oil-repellent coating layer is formed in only the two locations described above, so the amount of oil-repellent coating agent used during manufacturing can be reduced compared to the first embodiment, further simplifying the manufacturing process. Also, because the cage 16 is obtained by applying an oil-repellent coating to the inner diameter surface of a conventional stamped cage, it can be manufactured without significantly changing the shape of the existing product.

[0051] Although the embodiments of the present invention have been described above with reference to the drawings, the ball bearing of the present invention is not limited to these. For example, the present invention can be applied to any ball bearing, such as an angular contact ball bearing or a thrust ball bearing.

[0052] The uses of the ball bearing of the present invention are not particularly limited, but it can be used, for example, as deep groove ball bearings for automotive electrical equipment and accessories such as deep groove ball bearings for fan coupling devices, deep groove ball bearings for automotive alternators, and deep groove ball bearings for idler pulleys.

[0053] The ball bearing of the present invention can also be applied to, for example, flying cars, which have been attracting attention in recent years as an alternative means of transportation to automobiles. Flying cars are expected to solve various social problems and are expected to be used in a variety of situations, including intra-regional transportation, inter-regional transportation, tourism and leisure, emergency medical care, and disaster relief.

[0054] Vertical take-off and landing aircraft (VTOL) are attracting attention as flying cars. VTOLs can ascend and descend vertically between the sky and takeoff and landing sites, eliminating the need for runways and offering superior convenience. In particular, in recent years, due to societal demands for reducing CO2 emissions, electric vertical take-off and landing aircraft (eVTOL), which fly using batteries and motors, have become the mainstream of development.

[0055] An electric vertical take-off and landing aircraft equipped with a ball bearing of the present invention will be described with reference to Fig. 6. The electric vertical take-off and landing aircraft 21 shown in Fig. 6 is a multicopter having a main body 22 located in the center of the aircraft body and four drive units 23 arranged on the front, rear, left and right sides. The drive units 23 are devices that generate lift and thrust for the electric vertical take-off and landing aircraft 21, and the electric vertical take-off and landing aircraft 21 flies when driven by the drive units 23. The electric vertical take-off and landing aircraft 21 may have more than one drive unit 23, and is not limited to four.

[0056] The main body 22 has a living space large enough to accommodate a crew member (for example, one to two people). This living space is provided with an operating system for determining the direction of travel and altitude, and instruments for indicating altitude, speed, flight position, etc. Four arms 22a extend from the main body 22, and a drive unit 23 is provided at the tip of each arm 22a. In FIG. 6, a circular ring portion that covers the rotating periphery of the rotor 24 is integrally provided on the arm 22a to protect the rotor 24. In addition, a skid 22b that supports the aircraft during landing is provided below the main body 22.

[0057] The drive unit 23 has a rotor 24 and a motor 25 that rotates the rotor 24. In the drive unit 23, a pair of rotors 24 are provided on both axial sides of the motor 25. Each rotor 24 has two blades extending radially outward.

[0058] The main body 22 is provided with a battery (not shown) and a control device (not shown). The control device is also called a flight controller. The electric vertical take-off and landing aircraft 21 is controlled by the control device, for example, as follows: The control device outputs a command to change the rotation speed to the motor 25 that should adjust the lift based on the difference between the current attitude and the target attitude. Based on this command, an amplifier provided in the motor 25 adjusts the amount of power sent from the battery to the motor 25, and the rotation speed of the motor 25 (and the rotor 24) is changed. Furthermore, the adjustment of the rotation speed of the motors 25 is performed simultaneously for multiple motors 25, and the attitude of the aircraft is determined thereby.

[0059] Figure 7 shows a partial cross section of the motor in the drive unit. In Figure 7, the above-mentioned rotor is attached to one end (upper side of the figure) of the rotating shaft 27 of the motor 25, and a rotor is attached to the other end (lower side of the figure). The rotor is disposed opposite a stator fixed to the housing and is rotatable relative to the stator. The motor 25 can be configured as an outer rotor brushless motor or an inner rotor brushless motor.

[0060] In FIG. 7, motor 25 includes housing (device housing) 26, a rotor (not shown), a stator (not shown), an amplifier (not shown), and two deep groove ball bearings 31, 31. Housing 26 has an outer cylinder 26a and an inner cylinder 26b, with a coolant flow path 26c provided between them. By flowing a coolant through this flow path 26c, excessive temperature rise can be prevented. Furthermore, deep groove ball bearings 31, 31 rotatably support rotating shaft 27 within inner cylinder 26b. Deep groove ball bearing 31 is equipped with a seal member 35, and is a bearing in which grease is sealed inside the bearing, and corresponds to the ball bearing of the present invention.

[0061] In deep groove ball bearing 31, the outer diameter shape of outer ring 33 is approximately the same as the shape of the fitting portion on the inner periphery of the housing, and it is fitted directly into housing 26 without an intervening bearing housing or the like. Inner ring spacer 28 and outer ring spacer 29 are inserted between deep groove ball bearings 31 and 31, and preload is applied.

[0062] While electric vertical take-off and landing (EVL) aircraft require high levels of safety, they are also expected to operate under high-speed rotation conditions. The ball bearing of the present invention has low torque and can suppress grease leakage even when the amount of grease packed inside the bearing is increased, making it suitable for use in EVL aircraft, which are expected to operate under high-speed rotation. Furthermore, it can reduce the adverse effects of grease leakage on other components, thereby contributing to the safe flight of the EVL aircraft.

[0063] The bearing configuration in the drive unit is not limited to the configuration in Fig. 7. In Fig. 7, the rotating shaft of the motor and the rotating shaft of the impeller are the same rotating shaft, but the rotating shaft of the motor and the rotating shaft of the impeller may be connected via a transmission mechanism. In this case, the ball bearing that supports the rotating shaft in the drive unit may be the ball bearing that supports the rotating shaft of the motor, or may be the ball bearing that supports the rotating shaft of the impeller. [Industrial Applicability]

[0064] The ball bearing of the present invention can be manufactured easily and, even if the amount of grease sealed inside the ball bearing is increased, grease leakage can be suppressed at low torque, making it widely usable as a ball bearing in a variety of applications. [Explanation of symbols]

[0065] 1 ball bearing 2. Inner circle 2a Inner ring raceway groove 2b Inner ring seal groove 2c Shoulder 3 outer ring 3a Outer ring raceway groove 3b Outer ring seal groove 3c Shoulder 3D contact surface 4 balls 5 Sealing material 6 Cage 6a Pocket 6b Connecting plate part 6c Inner diameter surface 11 Ball bearings 16 Cage 16c Inner diameter surface 21 Electric vertical take-off and landing aircraft 22 Main body 23 Drive unit 24 rotor blades 25 motor 26 Housing 27 Rotation axis 28 Inner ring spacer 29 Outer ring spacer 31 Deep groove ball bearing 32 Inner circle 33 Outer ring 34 balls 35 Sealing material

Claims

1. A ball bearing comprising an inner ring having an inner ring raceway groove on its outer circumference, an outer ring having an outer ring raceway groove on its inner circumference, a plurality of balls assembled between the inner ring raceway groove and the outer ring raceway groove, a cage for holding the plurality of balls, and a seal member having one end fixed to an outer ring seal groove provided in the outer ring and the other end contacting an inner ring seal groove provided in the inner ring, wherein grease is sealed inside the bearing, the ball bearing has an oil-repellent coating layer only on a surface of a shoulder portion of the outer diameter surface of the inner ring that is disposed between the inner ring raceway groove and the inner ring seal groove, and on an inner diameter surface of the cage that faces the outer diameter surface of the inner ring, the ball bearing does not have an oil-repellent coating layer on a surface of a shoulder portion of the inner diameter surface of the outer ring that is located between the outer ring raceway groove and the outer ring seal groove, and has the oil-repellent coating layer on an abutment surface of the inner diameter surface of the outer ring that is abutted in the axial direction by the seal member, The ball bearing is characterized in that the oil-repellent coating layer is not provided on the surface of the seal member.

2. 2. The ball bearing according to claim 1, wherein the oil-repellent coating layer is a film made of a fluorine-based coating agent.

3. 3. The ball bearing according to claim 1, wherein the retainer is a crown-shaped ball bearing retainer consisting of an annular body having a plurality of pocket portions, each of which is partially open on one side to hold the balls, and a connecting plate portion that connects adjacent pocket portions.

4. the ball bearing is mounted on an electric vertical take-off and landing aircraft that flies by rotation of the rotors and includes a plurality of drive units each having a rotor and a motor that rotates the rotors, 4. The ball bearing according to claim 1, wherein the ball bearing supports a rotating shaft in the drive unit.

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