Ball bearing and method for sealing grease in ball bearing

Abstract

A ball bearing according to the present invention comprises an outer ring 1 and an inner ring 2, a plurality of balls 3 that are provided between the outer ring 1 and the inner ring 2 so as to be able to roll, a cage 4 that has pockets 4a that respectively hold the balls 3, shield plates 5 that close a bearing space S that is between the outer ring 1 and the inner ring 2 on respective sides in the axial direction, and grease G that is sealed in the bearing space S. In an initial sealed state, the grease G forms a seamless, continuous ring in the circumferential direction between an inner circumferential surface of the outer ring 1 and an outer circumferential surface of the inner ring 2 and contacts the balls 3 and an inner surface of the shield plates 5. The present invention thereby reduces noise and torque while maintaining the adhesion of the grease.

Description

Ball bearing and method for sealing grease in ball bearing

[0001] The present invention relates to a ball bearing and a method for sealing grease in a ball bearing.

[0002] Conventionally, in grease-sealed ball bearings, in which grease is sealed in the bearing space between the outer ring and the inner ring, various sealing methods have been proposed to achieve quieter operation and lower torque (see, for example, Patent Documents 1 to 3).

[0003] Patent Document 1 describes that the grease is filled so that it adheres to the outer axial side of the raceway groove on the inner surface of the outer ring and forms a continuous ring shape along the circumferential direction, and that the grease is filled with a gap between the inner ring and the grease so that the inner peripheral portion of the grease does not come into contact with the outer peripheral portion of the inner ring, thereby reducing rotational torque.

[0004] A known method of applying grease in an annular shape is to rotate a nozzle 100 and a raceway ring 101 relative to each other while discharging grease G from the nozzle 100, as shown in Fig. 5. When grease G is applied in an annular shape all around the circumference, an overlapping portion X is formed between the starting point and the end point, as shown in Fig. 6, causing variations in the height of the grease G to be filled. This overlapping portion X of the grease G may come into contact with the rolling elements 102 and the cage 103 more than necessary, which may result in an increase in torque.

[0005] In the grease application method described in Patent Document 2, by providing a gap between the starting point and the end point, it is possible to prevent the grease from coming into contact with the rolling elements or the cage more than necessary, thereby achieving low torque in the rolling bearing.

[0006] Japanese Patent Publication No. 2013-204679 Japanese Patent Publication No. 2021-139497 Japanese Patent Publication No. 2021-139498

[0007] However, with the sealing method described in Patent Document 2, there are concerns about torque fluctuations and vibration noise when the balls pass through the grease, as well as a decrease in the adhesive strength of the annular grease.

[0008] The present invention has been made in light of the above-mentioned problems, and aims to provide a ball bearing that can achieve quieter operation and lower torque while maintaining grease adhesion, and a method for sealing grease in a ball bearing.

[0009] The above object of the present invention is achieved by the following configuration: [1] A ball bearing comprising an outer ring having an outer ring raceway groove on its inner peripheral surface, an inner ring having an inner ring raceway groove on its outer peripheral surface, a plurality of balls arranged to roll freely between the outer ring raceway groove and the inner ring raceway groove, a cage having a plurality of pockets for holding the plurality of balls, a pair of sealing members that close a bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring on both axial sides, and grease sealed in the bearing space, wherein the grease, in an initially sealed state, is formed in a continuous ring shape without seams in the circumferential direction between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and is in contact with the plurality of balls and the inner surface of the sealing members. a retainer having pockets for holding the balls, a pair of sealing members that close a bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring on both axial sides; and grease to be sealed in the bearing space, the method comprising the steps of: arranging a nozzle member having an annular oil supply port that communicates with the bearing space, on one axial side of the balls in the bearing space, with at least one of the pair of sealing members not attached to the outer ring or the inner ring; sealing the annular grease, which is continuous and seamless in the circumferential direction, into the bearing space from the oil supply port of the nozzle member so as to come into contact with the balls; and attaching the sealing member to the outer ring or the inner ring so that the grease comes into contact with the inner surface of the sealing member.

[0010] In this specification, the term "initial sealed state" refers to the state in which a pair of sealing members is attached to the outer ring or inner ring to assemble the ball bearing, and before operation or break-in begins.

[0011] According to the present invention, in the initially sealed state, the grease is formed into a continuous ring shape without seams in the circumferential direction between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and is in contact with the balls and the inner surface of the sealing member. This allows the grease to operate without coming into contact with the balls or cage more than necessary, achieving quieter operation and lower torque while maintaining grease adhesion.

[0012] Fig. 1 is a cross-sectional view showing a ball bearing according to one embodiment of the present invention. Fig. 2 is a diagram for explaining the process of sealing in grease by a nozzle member. Fig. 3 is a side view of the balls and cage showing the state in which the grease of this embodiment has been applied. Fig. 4 is a graph showing comparative data of the starting torque and the torque after 60 seconds of operation in a product of the present invention and a conventional product. Fig. 5 is a diagram showing a conventional grease sealing method. Fig. 6 is a side view of the balls and cage showing the state in which the conventional grease has been applied.

[0013] A ball bearing according to one embodiment of the present invention and a method for sealing grease in the ball bearing will be described below with reference to the drawings. Ball bearing 10 is composed of outer ring 1, inner ring 2, balls 3, cage 4, a pair of shield plates 5, and grease G. Ball bearing 10 in this example is for use in a motor, with outer ring 1 being the fixed ring and inner ring 2 being the rotating ring.

[0014] An outer ring raceway groove 1a is formed on the inner peripheral surface of the outer ring 1, and an inner ring raceway groove 2a is formed on the outer peripheral surface of the inner ring 2, and multiple balls 3 are arranged so as to be able to roll freely between the outer ring raceway groove 1a and the inner ring raceway groove 2a.

[0015] Mounting grooves 1b for shield plates 5 are formed at both axial ends of the inner peripheral surface of the outer ring 1. The pair of shield plates 5 are made of metal, with the inner peripheral edges of the shield plates 5 adjacent to the outer peripheral surface of the shoulder of the inner ring 2 with a specified gap between them. In this way, the pair of shield plates 5 close the bearing space S between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2 on both axial sides.

[0016] The cage 4 is a crown-shaped cage made of synthetic resin that is open on one axial side (the right side in FIG. 1) and has multiple pockets 4a (see FIG. 3) that respectively hold multiple balls 3. Specifically, the cage 4 has an annular portion 4b located on the other axial side (the left side in FIG. 1) of the balls 3, multiple pillar portions 4c extending axially from the annular portion 4b, and a pair of claw portions 4d provided at the tip of each pillar portion 4c. The balls 3 are held in the pockets 4a so that they partially protrude axially beyond the claw portions 4d of the cage 4.

[0017] 1, grease G is filled (applied) in the bearing space S between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2 on the opening side of the cage 4 so as to come into slight contact with the balls 3. In this embodiment, grease G is not filled in the space on the opposite side of the opening of the cage 4.

[0018] In the initially sealed state when the pair of shield plates 5 are attached to the mounting groove 1b of the outer ring 1, the grease G is pressed against and comes into contact with the inner surfaces of the shield plates 5. The grease G is sealed so that it comes into contact with the inner peripheral surface of the outer ring 1 but does not come into contact with the outer peripheral surface of the inner ring 2, which is the rotating ring. Furthermore, in this embodiment, it is preferable that the grease G does not come into contact with the tips of the claw portions 4d and column portions 4c of the cage 4 in the initially sealed state.

[0019] The grease G to be filled may be a urea-based or lithium-based grease having a consistency of 200 to 300.

[0020] 2, when the grease G is to be sealed in the bearing space S, the ball bearing 10 is placed on a support base (not shown) with the axial direction of the ball bearing 10 facing vertically, with the pair of shield plates 5 not attached to the outer ring 1. Then, a nozzle member 20 having an annular oil supply port 21 that communicates with the bearing space S is disposed on one axial side of the balls 3 in the bearing space S.

[0021] Nozzle member 20 has a cylindrical portion 22 whose outer peripheral surface fits into mounting groove 1b on the inner peripheral surface of outer ring 1 and whose inner peripheral surface fits into a groove shoulder on the outer peripheral surface of inner ring 2. The lower end of an annular fuel filler port 21 extending in the vertical direction opens into the lower surface of cylindrical portion 22, and the upper end of fuel filler port 21 extends axially and is connected to a plurality of holes 31 arranged at equal intervals in the circumferential direction.

[0022] Therefore, grease G is supplied from above the nozzle member 20, and after passing through the multiple holes 31, the grease G spreads circumferentially within the space of the oil fill port 21, and the spread grease G joins together to form a ring, and is sealed into the bearing space S from the oil fill port 21.

[0023] At this time, the annular grease G comes into contact with the surfaces of the balls 3 located on one axial side of the claws 4d of the cage 4. Furthermore, the radially intermediate position of the oil filler port 21 is offset radially outward from the pitch circle diameter of the balls 3, and in particular, in this embodiment, the inner peripheral surface of the oil filler port 21 is formed with a diameter slightly larger than the inner diameter of the groove shoulder of the outer ring 1, so that the annular grease G discharged from the oil filler port 21 adheres to the inner peripheral surface of the outer ring 1, which is the fixed ring, but is sealed away from the outer peripheral surface of the inner ring 2, which is the rotating ring.

[0024] After the grease is sealed in by the nozzle member 20, when the pair of shield plates 5 are attached to the attachment groove 1b of the outer ring 1, the grease G comes into contact with the inner surface of the shield plate 5 on one axial side. At this time, because the grease G is formed in a continuous ring shape without joints in the circumferential direction between the inner peripheral surface of the outer ring 1 and the outer peripheral surface of the inner ring 2, even if the grease G is pressed by the shield plate 5, the grease G does not come into contact with any of the claw portions 4d of the cage 4.

[0025] In a ball bearing filled with grease G in this manner, the grease G is in contact with the balls 3 in the initial sealed state, so that the base oil in the grease adheres to the balls 3, allowing the balls 3 to roll smoothly. Furthermore, because the grease G is spaced apart from the cage 4 in the initial sealed state, the grease G is less likely to be crushed, reducing the amount of thickener contained in the grease G that seeps into the outer ring raceway groove 1a and the inner ring raceway groove 2a, thereby suppressing an increase in rotational torque. In other words, the grease G comes into contact with the balls 3 while being spaced apart from the cage 4, allowing the base oil in the grease G to be discharged, allowing the balls 3 to roll smoothly with the influence of the thickener reduced. This allows the grease G to operate without coming into contact with the balls 3 or the cage 4 more than necessary, achieving quieter operation and low torque while maintaining grease adhesion.

[0026] <Test> Tests were carried out on the starting torque and the torque after 60 seconds using a ball bearing of a conventional type in which the nozzle and raceway are rotated relative to each other to apply grease around the circumference in an annular shape, as shown in Fig. 4, and a ball bearing of the type in which grease is sealed in an annular shape using the nozzle member 20 of this embodiment shown in Fig. 1. A crown-type cage was used as the cage, and a urea-based grease with a consistency of 265 was used as the sealed grease.

[0027] As shown in FIG. 4, the sealed ball bearing of this embodiment was confirmed to have a maximum reduction of 27% in starting torque and a maximum reduction of 32% in torque after 60 seconds compared to the conventional sealed ball bearing.

[0028] In addition, when an acrylic ring is used for the outer ring and the overlapping area at the start and end points in the conventional sealing method is observed from the circumferential direction, it was found that the grease penetrated deeply into the balls and cage and made contact with them, causing an increase in torque.

[0029] The present invention is not limited to the above-described embodiment, and modifications and improvements are possible as appropriate. For example, in the above embodiment, grease is sealed from the opening side of the crown type cage, but the present invention is not limited to this. Grease may be sealed from the annular portion side of the crown type cage, or from both the opening side and the back side of the annular portion. Furthermore, a cage to which grease has been applied in advance may be used in combination with the grease sealing method of the present invention. When grease is sealed from the back side of the annular portion of the crown type cage, the grease comes into contact with the annular portion, but is less likely to be crushed by the rotation of the cage than when the grease comes into contact with the claws on the opening side, thereby achieving low torque.

[0030] In the above embodiment, a shield plate is used as the sealing member of the present invention, but the sealing member of the present invention is not limited to this, and for example, a contact-type or non-contact-type sealing member may be used. Furthermore, the cage of the present invention is not limited to a crown-type cage but may be a cage having an annular pocket without an opening, and the material is not limited to synthetic resin but may be, for example, metal.

[0031] As described above, this specification discloses the following: (1) A ball bearing comprising an outer ring having an outer ring raceway groove on its inner peripheral surface, an inner ring having an inner ring raceway groove on its outer peripheral surface, a plurality of balls rollably arranged between the outer ring raceway groove and the inner ring raceway groove, a cage having a plurality of pockets for holding the plurality of balls, a pair of sealing members that close a bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring on both axial sides, and grease sealed in the bearing space, wherein, in an initially sealed state, the grease is formed into a continuous ring shape without seams in the circumferential direction between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and is in contact with the plurality of balls and the inner surface of the sealing member. With this configuration, the grease operates without coming into contact with the balls or the cage more than necessary, and quieter operation and lower torque can be achieved while maintaining grease adhesion.

[0032] (2) The ball bearing according to (1), wherein the grease is in contact with the inner peripheral surface of the outer ring, which is a fixed ring, but is not in contact with the outer peripheral surface of the inner ring, which is a rotating ring, in the initial sealed state. With this configuration, it is possible to suppress the action of centrifugal force on the grease, thereby achieving low torque.

[0033] (3) The ball bearing according to (1) or (2), wherein the cage is a crown-type cage that opens on one side in the axial direction, and the grease is not in contact with the crown-type cage in the initial sealed state. With this configuration, the grease is less likely to be crushed by the rotation of the cage, thereby achieving low torque.

[0034] (4) A method for sealing grease in a ball bearing comprising an outer ring having an outer ring raceway groove on its inner peripheral surface, an inner ring having an inner ring raceway groove on its outer peripheral surface, a plurality of balls arranged to roll freely between the outer ring raceway groove and the inner ring raceway groove, a cage having pockets for holding each of the plurality of balls, a pair of sealing members that close a bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring on both axial sides, and grease to be sealed in the bearing space, the method comprising the steps of: arranging a nozzle member having an annular oil supply port that communicates with the bearing space, on one axial side of the balls in the bearing space, with at least one of the pair of sealing members not attached to the outer ring or the inner ring; sealing the annular grease that is continuous without seams in the circumferential direction from the oil supply port of the nozzle member into the bearing space so that it comes into contact with the plurality of balls; and attaching the sealing member to the outer ring or the inner ring so that the grease comes into contact with the inner surface of the sealing member. With this configuration, the grease is operated without coming into contact with the balls or cage more than necessary, and quiet operation and low torque can be achieved while maintaining the adhesive strength of the grease.

[0035] This application is based on a Japanese patent application (Patent Application No. 2024-146432) filed on August 28, 2024, the contents of which are incorporated herein by reference.

[0036] REFERENCE SIGNS LIST 1 outer ring 1a outer ring raceway groove 2 inner ring 2a inner ring raceway groove 3 balls 4 cage 4a pocket 5 shield plate (sealing member) G grease S bearing space

Claims

1. A ball bearing comprising: an outer ring having an outer ring raceway groove on its inner peripheral surface; an inner ring having an inner ring raceway groove on its outer peripheral surface; a plurality of balls arranged to roll freely between the outer ring raceway groove and the inner ring raceway groove; a cage having a plurality of pockets for holding each of the plurality of balls; a pair of sealing members that seal, on both axial sides, the bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring; and grease sealed in the bearing space, wherein, in an initially sealed state, the grease is formed in a continuous ring shape without seams in the circumferential direction between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and is in contact with the plurality of balls and the inner surface of the sealing members.

2. A ball bearing according to claim 1, wherein, in the initially sealed state, the grease is in contact with the inner peripheral surface of the outer ring, which is the fixed ring, but is not in contact with the outer peripheral surface of the inner ring, which is the rotating ring.

3. A ball bearing according to claim 1 or 2, wherein the cage is a crown-type cage that opens on one axial side, and the grease is not in contact with the crown-type cage in the initial sealed state.

4. A method of sealing grease in a ball bearing comprising an outer ring having an outer ring raceway groove on its inner peripheral surface, an inner ring having an inner ring raceway groove on its outer peripheral surface, a plurality of balls arranged to roll freely between the outer ring raceway groove and the inner ring raceway groove, a cage having pockets for holding each of the plurality of balls, a pair of sealing members that close off on both axial sides the bearing space between the inner peripheral surface of the outer ring and the outer peripheral surface of the inner ring, and grease to be sealed in the bearing space, comprising the steps of: arranging a nozzle member having an annular oil supply port that communicates with the bearing space, on one axial side of the balls in the bearing space, with at least one of the pair of sealing members not attached to the outer ring or the inner ring; sealing the annular grease that is continuous without seams in the circumferential direction from the oil supply port of the nozzle member into the bearing space so that it comes into contact with the plurality of balls; and attaching the sealing member to the outer ring or the inner ring so that the grease comes into contact with the inner surface of the sealing member.

Images