Deep groove ball bearing

Abstract

To provide a cage for a deep groove ball bearing, the cage being hard to be broken even under a high-speed rotating environment of an electric vehicle speed reducer and a motor that are used in an environment where a dmn value is 850,000 or more, as in an electric vehicle.SOLUTION: The deep groove ball bearing includes the resin cage containing, as a reinforcement material, glass fibers, carbon fibers, or both. The reinforcement material has a number-average fiber length of 100 to 600 μm and a number-average fiber diameter of φ4 to φ18 μm.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention primarily relates to a cage for a ball bearing. [Background technology]

[0002] In deep groove ball bearings that support the motors and transmissions of hybrid and fuel cell vehicles, fiber-reinforced resins containing fibers to improve durability are used in the resin cage. For example, Patent Document 1 proposes the use of a crown-type cage molded from a nylon resin containing 15 to 35% by weight of glass fiber for rolling bearings for automobile transmissions used where dm·n≧650,000 (dm: pitch circle diameter of rolling elements, n: rotational speed). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4626183 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, as motors have become smaller with the spread of EVs, the motor support and the shaft of the reducer that is directly connected to the motor shaft are being exposed to an environment of dm·n≧850,000, which is even more severe than the range specified in Patent Document 1. In such a high-speed rotation environment, the toe side of the cage deforms in the outward direction due to strong centrifugal force, causing constant interference with the rolling elements or outer ring, which can cause the bearing to heat up.

[0005] In addition, centrifugal force caused by high-speed rotation acts on the steel balls, generating high stress when they come into contact with the cage, raising concerns that this could lead to the cage breaking.

[0006] In view of the above background, an object of the present invention is to provide a cage for a deep groove ball bearing which avoids constant interference with steel balls and the outer ring caused by deformation of the resin cage under high speed rotation. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides a bearing comprising an inner ring, an outer ring, balls arranged between the inner ring and the outer ring, and a cage having pockets that hold the balls in a circumferential direction, dmn={(D+d) / 2}×n D: Bearing outer diameter (mm) d: bearing inner diameter (mm) n: Rotation speed (min -1 ) In deep groove ball bearings used in environments where the dmn value specified in is 850,000 or more, The cage is a crown-type cage made of resin, The resin contains glass fiber, carbon fiber, or both as a reinforcing material, The reinforcing material used in the deep groove ball bearing has a number average fiber length of 100 μm or more and 600 μm or less, and a number average fiber diameter of φ4 μm or more and φ18 μm or less (Configuration 1).

[0008] Here, a configuration (configuration 2) can be employed in which the resin cage contains 15 mass % or more and 50 mass % or less of the reinforcing material.

[0009] In addition to configuration 1 or 2, A configuration (configuration 3) can be employed in which the resin forming the resin cage is a thermoplastic resin.

[0010] In addition to configuration 3, A configuration (configuration 4) in which the thermoplastic resin is a crystalline resin can be employed.

[0011] Furthermore, in addition to configuration 4, The crystalline resin may be polyamide, polyphenylene sulfide, or polyether ether ketone (Configuration 5).

[0012] In addition to configuration 1 or 2, A configuration (configuration 6) can be employed in which the resin forming the resin cage is a thermosetting resin.

[0013] In addition to configuration 6, A configuration (configuration 7) in which the thermosetting resin is a phenol resin can be employed.

[0014] The deep groove ball bearing according to any of these embodiments can be used in vehicles such as electric vehicles, hybrid vehicles, plug-in hybrid vehicles, or fuel cell vehicles. Effect of the Invention

[0015] It has been known to use glass fiber or the like as a reinforcing material, but this invention uses glass fiber or carbon fiber as a reinforcing material having a number average fiber length of 100 μm to 600 μm and a number average fiber diameter of φ4 μm to φ18 μm, thereby improving the strength of a resin cage containing a sufficient amount of the glass fiber or carbon fiber. Specifically, the resin cage can have a Young's modulus of 7 GPa to 22 GPa, which suppresses deformation due to centrifugal force during high-speed rotation and also suppresses deformation when contacting with steel balls, thereby preventing breakage of the cage. In deep groove ball bearings for electric vehicle reducers and motors that may be in an environment of dmn≧850,000 that may occur in electric vehicles, hybrid vehicles, plug-in hybrid vehicles, fuel cell vehicles, etc., it is possible to suppress deformation of the resin cage due to centrifugal force, thereby improving durability and safety in a high-speed rotation environment. [Brief description of the drawings]

[0016] [Figure 1A] FIG. 1 is an axial cross-sectional view showing an example of a deep groove ball bearing according to the present invention. [Figure 1B] FIG. 1B is an axial cross-sectional view of the cage in FIG. 1A, with the cross-sectional position changed. [Diagram 2] A perspective view of the cage used in Figs. 1A and 1B [Diagram 3] FIG. 1 is a perspective view showing an example of a gate of a cage DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. This embodiment is a deep groove ball bearing 10 equipped with a resin cage 14 that exhibits high strength by containing a predetermined reinforcing material.

[0018] 1A and 1B, deep groove ball bearing 10 includes inner ring 11, outer ring 12, multiple balls 13 arranged between inner ring 11 and outer ring 12, and cage 14 having pockets 19 that hold balls 13 in the circumferential direction. Hereinafter, deep groove ball bearing 10 will be referred to simply as bearing 10. Furthermore, the direction along the bearing central axis of bearing 10 will be referred to as the "bearing axial direction" or simply as the "axial direction", the direction perpendicular to the axial direction will be referred to as the "bearing radial direction" or simply as the "radial direction", and the circumferential direction around the bearing central axis will be referred to as the "bearing circumferential direction" or simply as the "circumferential direction".

[0019] The inner ring 11 has an inner ring outer diameter surface 15 formed with a concave inner ring raceway surface 16. The outer ring 12 has an outer ring inner diameter surface 17 formed with an outer ring raceway surface 18, which is also concave, at a position opposite to the inner ring raceway surface 16. The balls 13 are rotatably disposed between the inner ring raceway surface 16 and the outer ring raceway surface 18.

[0020] The inner ring 11 has a rotating shaft (not shown) fixed to its inner diameter portion, and rotates in the circumferential direction together with the rotating shaft. The outer ring 12 is a member such as a housing or gear (not shown), and is attached to a fixed member that bears the load from the rotating shaft. In this way, the bearing 10 supports the rotating shaft rotatably relative to the fixed member. The rotating shaft referred to here may be, for example, a rotating shaft of a drive motor equipped in an electric transport device such as an electric vehicle, or a rotating shaft of a reducer or speed increaser equipped in such an electric transport device. The bearing center axis of the bearing 10 and the rotation center axis of the rotating shaft are set coaxially.

[0021] FIG. 2 shows a perspective view of the cage 14 only. The cage 14 is a crown-shaped cage molded from a resin containing a reinforcing material. In conventional reinforcing materials, fibers with a length of about 1500 μm are used. The cage 14 has an annular base 20 and pillars 21, 21 that protrude from the base 20 in the axial direction and form a curved surface to surround the balls 13 as a pocket 19, which are provided at a predetermined interval along the circumferential direction. The space between the pillars 21, which are made up of a pair of pillars, forms a concave pocket 19. The outer diameter surface of the cage 14 is a curved surface (cylindrical surface) without any steps. The outer diameter surface and inner diameter surface of the cage 14 are connected at the pocket 19.

[0022] The tip of the pillar portion 21 is a retaining claw. The retaining claws of the pillar portions 21, 21 on both sides of the pocket 19 are curved in a direction approaching each other. Note that, between the pockets 19 adjacent to each other in the circumferential direction, recesses 22 are formed to separate the pillar portions 21 in FIG. 2, but the adjacent pillar portions 21, 21 may be connected to each other. The balls 13 held by the pockets 19 revolve between the inner ring raceway surface 16 and the outer ring raceway surface 18 while being held by the pockets 19.

[0023] The resin forming the cage 14 can be selected from thermoplastic resin or thermosetting resin as needed. In the case of thermoplastic resin, it is preferable to use a crystalline resin with high strength, as it is less likely to deform due to the centrifugal force caused by the rotation of the bearing. Specific examples of crystalline resins that are preferable in terms of strength include polyamide, polyphenylene sulfide, and polyether ether ketone. As a thermosetting resin, for example, a phenolic resin is preferably used.

[0024] A reinforcing material is contained in the resin forming the cage 14. As the reinforcing material, glass fiber or carbon fiber can be used, and the cage 14 may contain both of these.

[0025] The reinforcing material must have a number average fiber length of 100 μm or more and 600 μm or less. The number average fiber length is the total length of all the fibers measured divided by the number of fibers measured. If it is less than 100 μm, the decrease in strength represented by the flexural modulus and Young's modulus cannot be ignored, and in a situation where dmn is 850,000 or more, which is assumed as the usage environment, there is a risk that the steel balls will be held in place or that the outer ring will be interfered with by deformation due to centrifugal force. On the other hand, if it exceeds 600 μm, the strength will decrease conversely, and the retainer 14 may be fatigue-damaged by the stress caused by interference with the balls 13 accelerated by centrifugal force. If it is within the above range, deformation is suppressed even in a high-speed rotation environment, and the retainer 14 is less likely to interfere with the balls 13, making it possible to use it in a stable situation.

[0026] Furthermore, the standard deviation of the fiber length is preferably not more than 500. The smaller the standard deviation, the fewer irregularly long fibers there are, and the higher the reinforcing effect is, which is preferable.

[0027] The reinforcing material must have a number average fiber diameter of φ4 μm or more and φ18 μm or less. This number average fiber diameter is the value obtained by summing up the diameters of all the measured fibers and dividing it by the number of fibers measured. If it is thinner than φ4 μm, the strength improving effect as a reinforcing material may be insufficient. On the other hand, if it exceeds φ18 μm, it is too thick and difficult to handle as a reinforcing material.

[0028] The content of the reinforcing material in the resin forming the cage 14 is preferably 15% by mass or more and 50% by mass or less. If it is less than 15% by mass, there is a high possibility that even if the reinforcing material is in the above range, the strength improving effect will be insufficient. On the other hand, if it exceeds 50% by mass, it becomes difficult to handle the resin, and there is a high possibility that the gate will become clogged during the manufacture of the cage 14, making it impossible to manufacture.

[0029] FIG. 3 shows an example of the position of the gate 31 provided in the mold when forming the cage 14 by injection molding. In the case of a single-point gate, the gate 31 is provided at a location located on one of the outer periphery of the pillar portion 21. A resin composition 32 containing the reinforcing material and kneaded with a resin is injected from the gate 31 to be molded. Note that this is just one example, and gates may be provided at multiple locations, or may be provided at a location other than the pillar portion 21. The type of gate can be appropriately selected from a pin gate, a submarine gate, and a disk gate.

[0030] The cage 14 manufactured under the above conditions preferably has a Young's modulus of 7 GPa or more and 22 GPa or less. If it is less than 7 GPa, deformation may become significant in an environment where dmn is 850,000 or more. On the other hand, even if it is within the above range, it is not realistic to exceed 22 GPa.

[0031] According to this configuration, dmn={(D+d) / 2}×n D: Bearing outer diameter (mm) d: bearing inner diameter (mm) n: Rotation speed (min -1 ) Under high-speed conditions where the dmn value, as defined by the formula (1), is 850,000 or more at the maximum rotational speed, deformation of the cage 14 is suppressed, enabling stable application of the bearing 10. In environments where dmn is 850,000 or more, the bearing 10 can be used as a bearing that supports the reducer and motor of an electric vehicle, such as an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, or a fuel cell vehicle. EXAMPLES

[0032] The present invention will be described in more detail below with reference to the data obtained by carrying out the present invention. First, the materials used will be described. PA66+GF (a mixture of nylon 66 and glass fiber. Glass fiber content: 25% by mass) PA9T+GF (a mixture of nylon 9T and glass fiber. Glass fiber content: 30% by mass) PA66+CF (a mixture of nylon 66 and carbon fiber. Carbon fiber content: 20% by mass)

[0033] (Examples 1 to 3) Using each of the above materials, a cage having the shape shown in FIG. 2 was manufactured by injection molding. Small pieces were cut out from the once manufactured cage, and the resin was burned off to recover the fibers contained therein. At least 30 randomly collected fibers were identified (39 in this example) and photographed. The fiber length and fiber diameter were measured for each of the photographed fibers. The results are shown in Table 1. In Example 1, the number average fiber length was 290 μm and the standard deviation was 230 μm. The number average fiber diameter was 13 μm. In Example 2, the number average fiber length was 250 μm and the standard deviation was 150 μm. The number average fiber diameter was 11 μm. In Example 3, the number average fiber length was 260 μm and the standard deviation was 120 μm. The number average fiber diameter was 6 μm.

[0034] [Table 1]

[0035] <Measurement of Young's modulus> Measurements were performed in accordance with JIS K7161 (ISO527). [Explanation of symbols]

[0036] 11. Inner Circle 12 Outer ring 13 balls 14 Cage 15 Inner ring outer diameter surface 16 Inner ring raceway surface 17 Outer ring bore surface 18 Outer ring raceway 19 Pocket 20 base 21 Pillar section 22 Recess Gate 31 32 Resin composition

Claims

1. The bearing comprises an inner ring (11), an outer ring (12), balls (13) disposed between the inner ring (11) and the outer ring (12), and a cage (14) having pockets (19) for holding the balls (13) along a circumferential direction, dmn={(D+d) / 2}×n D: Bearing outer diameter (mm) d: bearing inner diameter (mm) n: Rotation speed (min －１ ) In deep groove ball bearings used in environments where the dmn value specified in is 850,000 or more, The cage (14) is a crown-type cage made of resin, The resin contains glass fiber, carbon fiber, or both as a reinforcing material, The reinforcing material has a number average fiber length of 100 μm or more and 600 μm or less, and a number average fiber diameter of φ4 μm or more and φ18 μm or less.

2. The resin cage contains the reinforcing material in an amount of 15% by mass or more and 50% by mass or less.

2. A deep groove ball bearing according to claim 1.

3. 2. The deep groove ball bearing according to claim 1, wherein the resin forming the resin cage is a thermoplastic resin.

4. 4. The deep groove ball bearing according to claim 3, wherein the thermoplastic resin is a crystalline resin.

5. 5. The deep groove ball bearing according to claim 4, wherein the crystalline resin is any one of polyamide, polyphenylene sulfide, and polyether ether ketone.

6. 2. The deep groove ball bearing according to claim 1, wherein the resin forming the resin cage is a thermosetting resin.

7. 7. The deep groove ball bearing according to claim 6, wherein the thermosetting resin is a phenolic resin.

8. A vehicle which is an electric vehicle, a hybrid vehicle, a plug-in hybrid vehicle, or a fuel cell vehicle, and which uses the deep groove ball bearing according to any one of claims 1 to 7.

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