Ball bearing and method for applying grease to ball bearing

Abstract

This ball bearing comprises: an inner race (1) and an outer race (2), one of which is a rotating race and the other a non-rotating race; a plurality of balls (3) which are arranged with freedom to roll between the inner race (1) and the outer race (2); a retainer (4) which has an opening portion at one end, in the axial direction, of each pocket (41) for holding each of the plurality of balls (3); a shielding plate (50) which close a space between the inner ring (1) and the outer ring (2), at both ends in the axial direction; and grease (6) which is enclosed in a space (8) surrounded by the inner race (1), the outer race (2), the balls (3), and the shielding plate (50). During initial sealing, the grease (6) is in contact with the balls (3) and is separated from the retainer (4), on the opening portion side of the retainer (4) in the space (8).

Description

Ball bearing and method of applying grease to ball bearing

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

[0002] Conventionally, ball bearings have been proposed that have an inner ring and an outer ring, one of which is a rotating ring and the other a non-rotating ring, and a plurality of balls arranged freely to roll between the inner ring and the outer ring. One type of conventional ball bearing is a ball bearing that is used while being filled with grease (a so-called grease-filled ball bearing), and for example, one that has shield plates that seal the gap between the inner ring and the outer ring at both axial ends.

[0003] Patent Document 1 describes a ball bearing in which grease is sealed in a space surrounded by an inner ring, an outer ring, balls, and a shield plate, and the grease is arranged over the entire circumferential surface of the non-rotating ring (the inner surface of the groove shoulder of the outer ring).

[0004] Japanese Patent Application Publication No. 2014-129872

[0005] However, when conventional ball bearings that are initially filled with grease are directly operated, the running torque can increase due to the effect of the grease's stirring resistance, so the running torque is usually reduced by performing a break-in period, etc. However, there is a demand for ball bearings that can reduce the running torque by shortening the break-in period or even without a break-in period, and there is room for improvement.

[0006] The present invention has been made in light of the above-mentioned problems, and aims to provide a ball bearing that can achieve low torque even without break-in, similar to that achieved after break-in, and a method for applying grease to a ball bearing.

[0007] Therefore, the above-mentioned object of the present invention is achieved by the following configurations (1) to (5) of a ball bearing: (1) A ball bearing comprising an inner ring and an outer ring, one of which is a rotating ring and the other is a non-rotating ring, a plurality of balls arranged to roll freely between the inner ring and the outer ring, a cage having an opening at one axial end of each pocket that holds the plurality of balls, a shield plate that closes the space between the inner ring and the outer ring at both axial ends, and grease sealed in a space surrounded by the inner ring, the outer ring, the balls, and the shield plate, wherein the grease is arranged so as to come into contact with the balls, and is arranged over the entire circumferential surface of the non-rotating ring that forms the space on the side of the opening of the cage, and is arranged at a distance from the cage. (2) The ball bearing according to (1) above, wherein the cage holds the balls in the pockets with portions of the balls exposed to the opening side. (3) The ball bearing according to (1) or (2) above, wherein a raceway in which the plurality of balls can roll is defined between the inner ring and the outer ring, an open end of the cage is located within the raceway, and the grease is located outside the raceway. (4) The ball bearing according to any one of (1) to (3) above, wherein the grease is disposed apart from the rotating ring. (5) A method of applying grease to a ball bearing comprising an inner ring and an outer ring, one of which is a rotating ring and the other is a non-rotating ring; a plurality of balls arranged to roll freely between the inner ring and the outer ring; a cage having an opening at one axial end of each pocket that holds the plurality of balls; a shield plate that closes the space between the inner ring and the outer ring at both axial ends; and grease sealed in a space surrounded by the inner ring, the outer ring, the balls, and the shield plate, the method comprising the step of bringing the grease into contact with the balls and separating them from the cage on the opening side of the cage on the peripheral surface of the non-rotating ring that forms the space, and applying the grease over the entire circumferential area of ​​the peripheral surface.

[0008] According to the configurations (1) and (5), for example, in an initially sealed state, the grease is arranged so as to contact the balls, and is arranged over the entire circumferential area of ​​the circumferential surface of the non-rotating ring that forms the space, toward the opening of the cage, and is arranged at a distance from the cage. As a result, the above configuration allows the balls to roll more smoothly than when the grease is not in contact with the balls, and the grease is less likely to be crushed than when the grease is in contact with the cage. This reduces the amount of thickener contained in the grease that enters the raceway defined between the inner ring and the outer ring, thereby suppressing an increase in rotational torque. In other words, according to the above configuration, the grease contacts the balls while being spaced from the cage, thereby discharging the grease's base oil, thereby enabling the balls to roll smoothly with the influence of the thickener reduced. Thus, according to the above configuration, factors that increase rotational torque are eliminated, and low torque can be achieved without a break-in period, similar to that after a break-in period.

[0009] According to the configuration (2) above, the retainer holds the balls in the pocket with a portion of the balls exposed at one axial end, thereby properly maintaining the contact state between the grease and the balls and the separation state between the grease and the retainer.

[0010] According to the above configuration (3), the open end of the cage is located inside the raceway and the grease is located outside the raceway, so that the separation state between the grease and the cage is maintained more appropriately.

[0011] According to the configuration (4) above, the grease is positioned away from the rotating ring, so that the grease is less likely to be crushed even when the bearing space is narrow, compared to a ball bearing in which a predetermined amount of grease is applied to the surface of the rotating ring as well (not just a small amount, but, for example, an amount equivalent to that of the non-rotating ring).

[0012] According to the present disclosure, it is possible to provide a ball bearing that can achieve low torque even without break-in, similar to that after break-in, and a method for applying grease to a ball bearing.

[0013] Fig. 1 is a cross-sectional view showing a ball bearing according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. Fig. 4 is a view corresponding to Fig. 2 showing a ball bearing according to a comparative example. Fig. 5 is a graph showing the evaluation results, with (a) showing the working example and (b) showing the comparative example.

[0014] <One embodiment> An example of an embodiment of a ball bearing and a method of applying grease to a ball bearing according to the present invention will be described below with reference to the drawings. This ball bearing is used, for example, in a vacuum pump. Note that the present invention is not limited to the embodiment described below, and modifications, improvements, etc. are possible as appropriate. Furthermore, the material, shape, dimensions, number, location, etc. of each component in the embodiment described below are not limited as long as the present invention can be achieved.

[0015] Fig. 1 is a cross-sectional view showing a ball bearing according to one embodiment of the present invention. Fig. 2 is a cross-sectional view taken along line A-A in Fig. 1. Fig. 3 is a cross-sectional view taken along line B-B in Fig. 1. This ball bearing is composed of an inner ring 1, an outer ring 2, balls 3, a cage 4, a shield plate 50, and grease 6. In this example, the inner ring 1 is a rotating ring, and the outer ring 2 is a non-rotating ring.

[0016] A raceway 7 for the balls 3 is defined between the inner ring 1 and the outer ring 2. Specifically, an inner ring raceway groove 12 constituting the raceway 7 is formed in the axial center (left-right direction in FIG. 1 ) of the groove shoulder outer peripheral surface 11 of the inner ring 1, and an outer ring raceway groove 22 constituting the raceway 7 is formed in the axial center of the groove shoulder inner peripheral surface 21 of the outer ring 2.

[0017] Mounting grooves 23 for shield plates 50 are formed at both axial ends of the groove shoulder inner circumferential surface 21 of the outer ring 2. The shield plate 50 is made of metal, and the inner peripheral edge of the shield plate 50 forms a proximity portion 501 that is close to the groove shoulder outer circumferential surface 11 of the inner ring 1 with a specified gap. This proximity portion 501 is not bent axially inward. The outer peripheral edge of the shield plate 50 forms a fixing portion 52 that is fixed to the mounting grooves 23 formed in the groove shoulder inner circumferential surface 21 of the outer ring 2.

[0018] The cage 4 is a crown-shaped cage made of synthetic resin, and has a pocket 41 that is open on one axial side (the right side in FIG. 1 ). The cage 4 is formed so that the balls 3 are held in the pocket 41 with a portion of the balls 3 exposed on the opening side. In other words, the depth of the pocket 41 is smaller than the diameter of the balls 3. The cage 4 is also formed so that an open end 42 (so-called claw portion, etc.) is located inside the raceway 7.

[0019] As shown in Figure 1, grease 6 is applied (enclosed) to the groove shoulder inner peripheral surface 21 of the outer ring 2 on the opening side of the cage 4 in the space 8 (bearing space) surrounded by the inner ring 1, outer ring 2, balls 3, and shield plate 50, so as to come into slight contact with the balls 3. Note that grease 6 is not applied to the space on the opposite side of the cage 4 opening.

[0020] 2, the grease 6 is applied (enclosed) to the groove shoulder inner peripheral surface 21 of the outer ring 2 so as to be located outside the raceway 7, and does not contact the cage 4 (specifically, the open end 42). Note that the grease 6 is not applied to the cage 4 (specifically, the open end 42).

[0021] As shown in Figure 3, the grease 6 is applied (enclosed) over the entire circumferential area of ​​the groove shoulder inner circumferential surface 21 of the outer ring 2. More specifically, the grease 6 is configured by a plurality of spherical grease particles 6a arranged without gaps over the entire circumferential area of ​​the groove shoulder inner circumferential surface 21 of the outer ring 2. Note that the grease 6 is not applied to the groove shoulder outer circumferential surface 11 of the inner ring 1.

[0022] The grease 6 is applied (filled) from the opening side of the cage 4 before the shield plate 50 is attached, using, for example, a nozzle with multiple holes, so that multiple spherical grease particles 6a are distributed without gaps over the entire circumferential direction of the groove shoulder inner circumferential surface 21 of the outer ring 2. With this method, a conventional grease filling device can be used, so no new equipment is required and production costs do not increase.

[0023] According to this embodiment, by arranging the grease 6 so that it contacts the balls 3 when initially filled, the base oil in the grease adheres to the balls, allowing the balls 3 to roll more smoothly than when the grease 6 is not in contact with the balls 3. Furthermore, by arranging the grease 6 spaced apart from the cage 4 in the initial filled state, the grease 6 is less likely to be crushed than when the grease 6 is not spaced apart from (in contact with) the cage 4. This reduces the amount of thickener contained in the grease 6 that enters the raceway 7, thereby suppressing an increase in rotational torque. In other words, by having the grease 6 contact the balls 3 while spaced apart from the cage 4, the base oil in the grease 6 is discharged, allowing the balls 3 to roll more smoothly with a reduced effect of the thickener. As such, according to this embodiment, factors that increase rotational torque are eliminated, and low torque can be achieved without a break-in period, similar to that after a break-in period.

[0024] Furthermore, according to this embodiment, the retainer 4 holds the balls 3 in the pocket 41 with a portion of the balls 3 exposed to the opening side (right side in Figure 2), thereby properly maintaining the contact state between the grease 6 and the balls 3 and the separation state between the grease 6 and the retainer 4.

[0025] Furthermore, according to this embodiment, the open end 42 of the retainer 4 is located within the raceway 7 and the grease 6 is located outside the raceway 7, thereby more appropriately maintaining the separation between the grease 6 and the retainer 4.

[0026] Furthermore, according to this embodiment, since the grease 6 is positioned away from the inner ring 1, which is the rotating ring, the grease 6 is less likely to be crushed even when the bearing space (space 8) is narrow, compared to a ball bearing in which a predetermined amount of grease 6 is also applied to the surface of the rotating ring (not a small amount, but, for example, an amount equivalent to that of the non-rotating ring).

[0027] <Test> In order to evaluate the rotational torque before break-in in the examples and comparative examples, a preload of 2.4 kgf was applied to each ball bearing of the examples and comparative examples in an environment of room temperature of 20°C for 100 minutes. －１ , 500 min －１ , and 3000 min －１The rotational torque was measured at each rotation speed. In the examples, the ball bearings shown in Figures 1 to 3 were used. In the comparative examples, the ball bearing shown in Figure 4 was used, in which the open end of the cage protrudes further toward the shield plate than the axial end of the balls, and the open end of this cage comes into contact with grease.

[0028] The evaluation results of the examples and comparative examples are shown in Figure 5. －１ and 500 min －１ Although there is no clear difference between the examples and the comparative examples, －１ In this case, the dynamic friction torque value is smaller in the example. The rotational torque is determined by the sum of the load term (magnitude of load: Ml) and the speed term (magnitude of rotational speed: Mv). Here, if the coefficient determined by the bearing type and lubrication method is f0, the dynamic viscosity of the oil is v0, and the rotational speed is n, the speed term (Mv) can be calculated as f0(v0·n)^(2 / 3)·dm^3. Based on this, when the rotational speed is in the low speed range of 100 min, －１ and 500 min －１ The impact is less noticeable at 3000 min. －１ In this case, the rotation speed is constant (for example, 1000 min －１ ) or more, it is considered that the difference between the Examples and the Comparative Examples became clear.

[0029] <Supplementary Notes> As explained above, this specification discloses the following: [1] A ball bearing comprising an inner ring (1) and an outer ring (2), one of which is a rotating ring and the other is a non-rotating ring, a plurality of balls (3) arranged to be able to roll between the inner ring (1) and the outer ring (2), a cage (4) having an opening at one axial end of each pocket (41) that holds the plurality of balls (3), a shield plate (50) that closes the gap between the inner ring (1) and the outer ring (2) at both axial ends, and grease (6) sealed in a space (8) surrounded by the inner ring (1), the outer ring (2), the balls (3), and the shield plate (50), wherein the grease (6) is A ball bearing arranged so as to come into contact with the balls (3), and arranged on the opening side of the cage (4) on the peripheral surface of a non-rotating ring that constitutes the space (8) (for example, the groove shoulder inner peripheral surface 21 of the outer ring 2) over the entire circumferential direction of the peripheral surface, and arranged at a distance from the cage (4). [2] The ball bearing according to [1] above, wherein the cage (4) holds the balls (3) in the pockets (41) with a portion of the balls (3) exposed to the opening side. [3] The ball bearing according to [1] or [2] above, wherein a raceway (7) in which the plurality of balls (3) can roll is defined between the inner ring (1) and the outer ring (2), an open end (42) of the cage (4) is located within the raceway (7), and the grease (6) is located outside the raceway (7). [4] The ball bearing according to any one of [1] to [3] above, wherein the grease (6) is arranged spaced apart from the rotating ring (for example, the inner ring 1).[5] A method of applying grease to a ball bearing comprising: an inner ring (1) and an outer ring (2), one of which is a rotating ring and the other is a non-rotating ring; a plurality of balls (3) arranged to be able to roll between the inner ring (1) and the outer ring (2); a cage (4) having an opening at one axial end of each pocket (41) that holds the plurality of balls (3); a shield plate (50) that closes the gap between the inner ring (1) and the outer ring (2) at both axial ends; and grease (6) sealed in a space (8) surrounded by the inner ring (1), the outer ring (2), the balls (3), and the shield plate (50), a step of applying the grease (6) to the entire circumferential surface of a non-rotating ring (e.g., groove shoulder inner circumferential surface 21 of the outer ring 2) on the opening side of the cage (4) by bringing the grease (6) into contact with the balls (3) and separating it from the cage (4).

[0030] This application is based on a Japanese patent application (Patent Application No. 2023-158521) filed on September 22, 2023, the contents of which are incorporated herein by reference.

[0031] According to the ball bearing and the method for applying grease to a ball bearing of the present invention, it is possible to realize a ball bearing and a method for applying grease to a ball bearing that can achieve low torque, for example, without the need for break-in operation, similar to that after break-in operation.

[0032] REFERENCE SIGNS LIST 1 inner ring 2 outer ring 3 ball 4 cage 6 grease 7 raceway 8 space 11 groove shoulder outer peripheral surface 12 inner ring raceway groove 21 groove shoulder inner peripheral surface 22 outer ring raceway groove 23 mounting groove 41 pocket 42 open end 50 shield plate 52 fixed portion 501 adjacent portion

Claims

1. A ball bearing comprising: an inner ring and an outer ring, one of which is a rotating ring and the other is a non-rotating ring; a plurality of balls arranged to roll freely between the inner ring and the outer ring; a cage having an opening at one axial end of each pocket that holds each of the plurality of balls; a shield plate that closes the space between the inner ring and the outer ring at both axial ends; and grease sealed in a space surrounded by the inner ring, the outer ring, the balls and the shield plate, wherein the grease is arranged so as to come into contact with the balls, and is arranged over the entire circumferential area of ​​the peripheral surface of the non-rotating ring that constitutes the space on the side of the opening of the cage, and is arranged at a distance from the cage.

2. A ball bearing according to claim 1, wherein the cage holds the balls in the pockets with a portion of the balls exposed on the opening side.

3. A ball bearing as claimed in claim 1, wherein a raceway within which the balls can roll is defined between the inner ring and the outer ring, the open end of the cage is located within the raceway, and the grease is located outside the raceway.

4. A ball bearing according to claim 1, wherein the grease is disposed spaced apart from the rotating ring.

5. A method of applying grease to a ball bearing comprising an inner ring and an outer ring, one of which is a rotating ring and the other is a non-rotating ring, a plurality of balls arranged to roll freely between the inner ring and the outer ring, a cage having an opening at one axial end of each pocket that holds each of the plurality of balls, a shield plate that closes the space between the inner ring and the outer ring at both axial ends, and grease sealed in a space surrounded by the inner ring, the outer ring, the balls, and the shield plate, comprising the steps of bringing the grease into contact with the balls and separating it from the cage on the opening side of the cage on the peripheral surface of the non-rotating ring that constitutes the space, and applying it over the entire circumferential area of ​​the peripheral surface.

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