Sealed structure

Abstract

By optimizing the amount of lubricant sealed inside and the volume of the space where the lubricant is sealed, lubricant leakage is prevented even under high-speed rotation. It provides a sealed structure to prevent this. [Solution] A sealing structure for a bearing device 1, comprising a sealing device 10 that seals a sealed space S1 between an inner member 4 and an outer member 2 that rotate coaxially relative to each other, wherein the sealing device, which is attached to either the inner member or the outer member, comprises an annular core material 11 and a sealing portion 17 made of an elastic material fixed to the core material and extending toward the other of the inner member and the outer member, wherein a lubricant is sealed in the sealed space and rolling elements 6 are rotatably interposed therein, and the volume of the annular space S2 formed between the sealed space and the sealing device is 90% or more of the amount of lubricant loaded.

Description

Technical Field

[0001] The present invention relates to a sealing structure of a bearing device provided with a sealing device for sealing a sealed space in which rolling elements are interposed.

Background Art

[0002] Conventionally, in a bearing device provided with rolling elements, a predetermined amount of lubricant is enclosed in order to maintain lubrication performance during rotation. Regarding the enclosed amount of this lubricant, as described in Patent Document 1 and Patent Document 2 below, it needs to be properly enclosed in consideration of heat generation of the bearing device, maintenance of lubricity, and prevention of leakage. Therefore, in Patent Document 1 below, the enclosed amount of grease enclosed in the bearing space is described as 25 to 35% of the space volume, and in Patent Document 2 below, it is described as 15 to 25%. Further, Patent Document 2 discloses a sealing member that forms a sealing groove on the shoulder of the inner ring and has an auxiliary lip portion that contacts the side surface of the sealing groove to prevent leakage of grease.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, if the enclosed amount of the lubricant is reduced, it is difficult to extend the life of the bearing device. Further, under high-speed rotation of the bearing device, the shear resistance of the fluid film of the lubricant increases, and the rotational torque also increases, so there is a possibility that the entire bearing device will generate heat. Furthermore, even when the sealing member is improved, when the bearing device rotates at high speed, the lubricant moves to the sealing member side and reaches the inner diameter side, so there is a possibility that leakage of the lubricant cannot be suppressed.

[0005] This invention has been made in view of the above circumstances, and aims to provide a sealing structure that prevents lubricant leakage even under high-speed rotation by optimizing the amount of lubricant sealed and the volume of the space in which the lubricant is sealed. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a sealing structure for a bearing device that seals a space to be sealed between an inner member and an outer member that rotate coaxially relative to each other, wherein the sealing device, which is attached to either the inner member or the outer member, comprises an annular core material and a sealing portion made of an elastic material fixed to the core material and extending toward the other of the inner member and the outer member, wherein a lubricant is sealed in the space to be sealed and rolling elements are rotatably interposed therein, and the volume of the annular space formed in the inner space of the sealing device is 90% or more of the amount of lubricant loaded.

[0007] To achieve the above objective, the present invention provides a sealing structure for a bearing device that seals a space to be sealed between an inner member and an outer member that rotate coaxially relative to each other, wherein the sealing device, which is attached to either the inner member or the outer member, comprises an annular core material and a sealing portion made of an elastic material fixed to the core material and extending toward the other of the inner member and the outer member, wherein a lubricant is sealed in the space to be sealed and rolling elements are rotatably interposed therein, the sealing device is provided between the ends of the inner member and the outer member, and the volume of the annular space formed between the edge of the rolling elements and the sealing device is 130% or more of the amount of lubricant loaded.

[0008] In the above-described sealing structure, the core material comprises a cylindrical portion fitted to one of the members and a disc portion connected to one axial end of the cylindrical portion and extending radially from that end, and the sealing portion comprises a bead portion covering the outer circumference of the cylindrical portion and a lip portion covering the leading end of the disc portion in the extending direction and extending toward the other member, and the sealing portion does not necessarily have to be disposed on either the side of the disc portion facing the sealed space or the side facing the external space.

[0009] In the above-described sealing structure, the core material comprises a cylindrical portion fitted to one of the members and a disc portion connected to one axial end of the cylindrical portion and extending radially from that end, and the sealing portion comprises a covering portion that covers the external space side of the disc portion and a lip portion that covers the leading end of the disc portion in the extending direction and extends toward the other member, and the disc portion may be provided with a recess.

[0010] In the above-described sealing structure, the core material comprises a cylindrical portion fitted to one of the members, and a disc portion connected to one axial end of the cylindrical portion and extending radially from that end. If the sealing portion includes a bead portion that covers the outer circumferential surface of the cylindrical portion and a lip portion that covers the leading end of the disc portion in the extending direction and extends toward the other member, the volume of the annular space may be the entire inner space of the sealing device surrounded by the cylindrical portion, the disc portion, and the lip portion on the side of the space to be sealed.

[0011] In the above-described sealing structure, the sealing portion may be made of conductive rubber having conductivity and include a lip portion that slides against the other member, and the sealing device may be configured as a conductive seal. [Effects of the Invention]

[0012] Because the sealing structure of the present invention has the above-described configuration, it is possible to optimize the amount of lubricant sealed and the volume of the space in which the lubricant is sealed, thereby preventing lubricant leakage even under high-speed rotation. [Brief explanation of the drawing]

[0013] [Figure 1] (a) is a diagram illustrating one embodiment of the sealing structure according to this embodiment, and is a schematic cross-sectional view showing an example of a bearing device. (b) is an enlarged cross-sectional view of part X in (a). [Figure 2] (a) and (b) are diagrams illustrating modified examples of the embodiment, and are schematic cross-sectional views showing the portion corresponding to part X. [Figure 3] (a) is a diagram illustrating a further modification of the embodiment, and is a schematic cross-sectional view showing the portion corresponding to part X. (b) is a schematic partial cross-sectional perspective view illustrating an example of a core material. [Figure 4] (a) and (b) are diagrams illustrating a test conducted to evaluate the relationship between the amount of lubricant sealed and the volume of the space in which the lubricant is sealed, and are schematic cross-sectional views of the bearing device used in that test. [Figure 5] This is a table summarizing the test results. [Modes for carrying out the invention]

[0014] The sealing structure according to this embodiment is a sealing structure for a bearing device 1 that includes a sealing device 10 that seals the space to be sealed S1 between an inner member 4 and an outer member 2 that rotate coaxially relative to each other. The sealing device 10 is attached to either the inner member 4 or the outer member 2. The sealing device 10 includes an annular core material 11 and an elastic sealing portion 17 fixed to the core material 11 and extending toward the other member of the inner member 4 or the outer member 2. A predetermined amount of lubricant is sealed in the space to be sealed S1 and rolling elements 6 are interposed so as to be rotatable, and the volume of the annular space S2 formed in the inner space of the sealing device 10 is 90% or more of the amount of lubricant loaded. Embodiments of the present invention will be described below with reference to the drawings. Note that in some figures, some of the detailed reference numerals that are indicated in other figures are omitted.

[0015] First, to describe the sealing structure according to the present embodiment, FIG. 1(a) schematically shows an example of a bearing device 1 in which a sealing device 10 is incorporated. In the example of FIG. 1(a), an example in which the sealing device 10 is attached to an outer member 2 is shown, and this sealing device 10 is incorporated in a bearing device 1 including an outer member 2 constituting an outer ring and an inner member 4 constituting an inner ring.

[0016] The bearing device 1 is configured such that, for example, the outer member 2 is fitted into a housing or the like, the shaft 9 is inserted into the inner member 4, and the inner member 4 is rotated together with the shaft 9 with respect to the outer member 2. The bearing device 1 is a rolling bearing device in which rolling elements (balls in the illustrated example) 6 are interposed between the outer member 2 and the inner member 4, and this bearing device 1 supports the shaft 9 of a transmission of various vehicles such as an automobile. An annular sealed space S1 is formed over the entire circumference between the outer member 2 and the inner member 4.

[0017] In the sealed space S1, a single row of rolling elements 6 is held by a retainer (cage) 7 and is interposed so as to be able to roll on the raceway ring 2a of the outer member 2 and the raceway ring 4a of the inner member 4, and a predetermined amount of lubricant (not shown) is enclosed in the sealed space S1. In the illustrated example, as the bearing device 1, a deep groove ball bearing provided with groove-shaped raceway rings 2a and 4a on the outer member 2 and the inner member 4 is exemplified.

[0018] As shown in FIG. 1(a), on both axial sides in the sealed space S1, sealing devices 10, 10 are mounted between the outer member 2 and the inner member 4 so as to sandwich the sealed space S1 therebetween. Then, the sealed space S1 is sealed by these sealing devices 10, 10 on both axial sides, and the intrusion of foreign matters or the like into the sealed space S1 and the leakage of the grease filled in the sealed space S1 to the outside are suppressed. Since the sealing devices 10, 10 provided on both axial sides have the same configuration, hereinafter, one of the sealing devices 10 will be described as an example. Further, the bearing device 1 in which the sealing device 10 is incorporated is not limited to the one having the above-described configuration, and may have various other configurations.

[0019] The sealing device 10 is formed in an annular shape concentric with the shaft 9 and has a core material 11 formed in an annular shape with a substantially L-shaped cross section, and a seal portion 17 made of an elastic material fixed to the core material 11 and extending toward the inner member 4. The core material 11 is an annular body formed from a metal material such as a stainless steel plate or a cold-rolled steel plate (SPCC). The core material 11 is fitted into an outer concave groove 3 formed to have a diameter larger than the inner peripheral surface 2b of the outer member 2 via a bead portion 14 and includes a cylindrical portion 12 extending along the axial direction, and a disk portion 13 extending radially from an end portion on one side (the external space 20) in the axial direction of the cylindrical portion 12.

[0020] The seal portion 17 includes a bead portion 14 fixed to the core material 11 and covering the outer peripheral surface 12b side of the cylindrical portion 12 of the core material 11, and a lip portion 15 covering the front end portion 13a on the front side in the extending direction (radial direction) of the disk portion 13 of the core material 11 and extending toward the inner member 4. The bead portion 14 is made of an elastic material such as a rubber material, and includes a bead base portion 14a fixed to the cylindrical portion 12 of the core material 11 and covering the outer peripheral surface 12b of the cylindrical portion 12, and a convex portion 14b formed to protrude radially outward so as to be fitted into the outer concave groove 3 formed to have a diameter larger than the inner peripheral surface 2b of the outer member 2. The lip portion 15 is made of an elastic material such as a rubber material, and includes a lip base portion 15a fixed so as to cover the front end portion 13a on the front side in the extending direction of the disk portion 13 of the core material 11, and a seal lip portion 15b formed to extend toward the inner side (axial center) in the radial direction of the sealing device 10. The tip end portion of the seal lip portion 15b is arranged to be in sliding contact with the side wall 5a of an inner concave groove 5 formed to have a diameter smaller than the outer peripheral surface 4b of the inner member 4. Also, the seal portion 17 is not arranged on any surface of the disk portion 13 on the sealed space S1 side or the external space 20 side. Further, the seal portion 17 may be made of conductive rubber having conductivity, and the sealing device 10 may be configured as a conductive seal.

[0021] One side of the cross-section of the sealing device 10 is roughly C-shaped, and the inner space 10a inside the sealing device 10, that is, the inner circumferential surface 12a of the cylindrical portion 12 of the core material 11, the inner circumferential surface 13b of the disc portion 13, and the inner circumferential surface 15c of the lip portion 15, constitutes an annular space S2 (shown by the dashed line in Figure 1(b)). The location where the sealing device 10 that seals the sealed space S1 of the bearing device 1 is placed is a limited space, but the inventors' tests showed that if the volume of the annular space S2 formed in the inner space 10a of the sealing device 10 is 90% or more of the amount of lubricant to be loaded, the amount of lubricant to be sealed and the volume of the space in which the lubricant is sealed are optimized, and it is possible to prevent the lubricant from leaking out of the sealing device 10 even under high-speed rotation. Furthermore, since the amount of lubricant sealed in the rolling elements 6 of the bearing device 1 is set according to the bearing device 1, it can be said that the annular space S2 formed by the sealing device 10 should be set so that the volume of the annular space S2 formed between the sealed space S1 and the sealing device 10 is 90% or more of the amount of lubricant sealed, according to the amount of lubricant sealed. Moreover, the annular space S2 functions as a pocket space for the lubricant that flows due to the rotation of the inner member 4, but it can be said that it was not possible to secure a sufficient annular space S2 within the limited installation space.Therefore, the sealing device 10 shown in Figure 1(b) can be applied when it is difficult to secure a large space for the installation of the sealing device 10, and by not placing rubber material or the like on the outer circumferential surface 13c and inner circumferential surface 13b of the disc portion 13, a larger annular space S2 is secured compared to the case in which a cover portion 16 as shown in Figure 2(a) is provided.The tests conducted by the inventor will be described in detail later with reference to Figures 4 and 5.

[0022] With the above configuration, the sealing device 10 prevents the intrusion of water, dust, etc. from the external space 20, and by making the volume of the annular space S2 formed between the sealed space S1 and the sealing device 10 90% or more of the amount of lubricant loaded, it is possible to prevent the lubricant from leaking out of the sealing device even under high-speed rotation. Therefore, the lifespan of the bearing device 1 can be extended. In addition, since the lubricant can be held in the annular space S2, it is possible to suppress the lubricant from reaching the lip portion 15, and even under high-speed rotation of the bearing device 1, shear resistance of the lubricant is less likely to occur, and the temperature rise of the entire bearing device 1 can be suppressed. Therefore, the lifespan of the bearing device 1 can be extended. Furthermore, in the case of a conventional sealing structure in which an annular space S2 is not secured, the volume of the annular space S2 is insufficient, and the lubricant that was around the rolling element 6 moves due to the rotation of the inner member 4 and reaches the tip of the seal lip portion 15b. However, with the above configuration, the volume of the annular space S2 is sufficiently secured, so it is difficult for a large amount of lubricant to reach the tip region of the seal lip portion 15b. Therefore, for example, if the seal lip portion 15b is made of a conductive rubber material, the conductivity will decrease when a non-conductive lubricant reaches it. However, with the above configuration, even when a non-conductive lubricant is used, it is possible to suppress the inhibition of the conductivity of the conductive rubber.

[0023] Next, a modified example of the sealing device 10 will be described with reference to Figures 2(a) to 3(b). Note that the descriptions of configurations and effects common to the above embodiment will be omitted.

[0024] The sealing device 10A shown in Figure 2(a) differs from the above embodiment in that the length dimension (axial length) of the cylindrical portion 12 is longer than that of the above embodiment in order to secure the largest possible annular space S2 in a limited installation space. It also differs from the above embodiment in that a covering portion 16 made of an elastic material is provided on the outer peripheral surface 13c side of the disc portion 13. With this configuration, by changing the length of the cylindrical portion 12 from, for example, 1.5 mm to 3.0 mm or more, the volume of the annular space S2 can be increased by more than double.

[0025] The sealing device 10B shown in Figure 2(b) differs from the sealing device 10A shown in Figure 2(a) in the configuration of the disc portion 13 and the lip portion 15. The disc portion 13 of the sealing device 10B is formed by bending the leading end 13a on the extending side so that it faces the tip of the seal lip portion 15b. In addition, the tip of the seal lip portion 15b is provided in a non-contact state with the inner groove 5. With the above configuration, even if the seal lip portion 15b is not in contact, a sufficient annular space S2 that functions as a pocket space for the lubricant is secured, so the space to be sealed S1 can be sealed without leakage of the lubricant.

[0026] The sealing device 10C shown in Figure 3(a) has a cylindrical portion 12 with a length dimension that is different from that of Figures 2(a) and 2(b) and is a commonly used dimension. However, in order to secure a larger annular space S2, a concave recess 18 is provided in the disc portion 13 that can expand the flow area of ​​the lubricant. Figure 3(b) is a cross-sectional perspective view showing only the core material 11 of the sealing device 10C shown in Figure 3(a). Multiple recesses 18 are provided along the circumferential direction of the disc portion 13 at appropriate intervals, and the recess 18 in the example shown is a circular through-hole. The shape of the recess 18 is not limited to a perfect circle, but may be elliptical, square, or a long rectangle along the circumferential direction. The bottom side of the recess 18 is covered with a cover portion 16 because it is necessary to prevent the intrusion of muddy water, etc., from the external space 20. According to the above configuration, the recessed portion 18 can be used as a flow region for the lubricant, and a larger annular space S2 can be secured compared to when there is no recessed portion 18.

[0027] Next, the tests conducted by the inventor will be described with reference to Figures 4 and 5. In these tests, the amount of lubricant loaded was varied under the following conditions, and the amount of grease leakage and the bearing temperature after 2 hours from the start of the test were measured. The shape and configuration of the sealing device 100 used in the test are the same, except that the length of the cylindrical part 12 is shorter than that of the sealing device 10B shown in Figure 2(b). Common components are denoted by the same reference numerals, and their explanations are omitted. Also, the sealing device 100 shown in Figures 4(a) and 4(b) is the same sealing device 100, and the table shown in Figure 5 shows the percentage when the standard for the volume of the annular space is changed, summarizing the test results. Therefore, "A" shown in Figure 4(a) refers to the entire area of ​​the inner space 10a surrounded by the sealed space S1 side of the cylindrical part 12, the disc part 13, and the lip part 15 (the dashed line portion shown in Figure 4(a)), and corresponds to (1) Volume A relative to the amount of applied grease in the table in Figure 5. Furthermore, "B" shown in Figure 4(b) represents the case where the annular space S3 includes not only the inner space 10a surrounded by the sealed space S1 side of the cylindrical portion 12, the disc portion 13, and the lip portion 15, but also the region surrounded by the space between the inner member 4 and the outer member 2 and the edge portion 6a of the rolling element 6 (the dashed line portion shown in Figure 4(b)), which corresponds to volume B for the amount of applied grease in the table of Figure 5.

[0028] <Test Conditions> Bearing used in the test: Single-row deep groove ball bearing, size 6206 Rotation speed: 20,000 rpm Exam duration: 2 hours Lubricant used: Urea grease manufactured by ENEOS Corporation Ambient temperature: Room temperature Radial load: No load Rubber material for the sealing part: NBR

[0029] <Test Results> <Test No. 1> When the volume A (the entire inner space 10a surrounded by the sealed space S1 side of the cylindrical portion 12, disc portion 13, and lip portion 15) was set to 65% of the applied grease amount, the amount of grease leakage was 0.25 g, and the bearing temperature 2 hours after the start of the test was 140°C. At this time, the volume B was 100% of the applied grease amount.

[0030] <Test No. 2> When volume A was set to 75% of the applied grease amount, the grease leakage was 0.05 g, and the bearing temperature 2 hours after the start of the test was 130°C. At this time, the ratio of volume B to the applied grease amount was 120%.

[0031] <Exam No. 3> When volume A was set to 90% of the applied grease amount, the grease leakage was 0g, and the bearing temperature 2 hours after the start of the test was 55°C. At this time, the ratio of volume B to the applied grease amount was 130%.

[0032] <Test No. 4> When volume A was set to 125% of the applied grease amount, the amount of grease leakage was 0g, and the bearing temperature was 50°C 2 hours after the start of the test. At this time, the ratio of volume B to the applied grease amount was 180%.

[0033] <Test No. 5> When volume A was set to 140% of the applied grease amount, the grease leakage was 0g, and the bearing temperature 2 hours after the start of the test was 45°C. At this time, the ratio of volume B to the applied grease amount was 200%.

[0034] <Summary of test results> It was found that if the volume A of the annular space S2 or the volume B of the annular space S3 is 75% or more of the lubricant load (Test No. 2), lubricant leakage is significantly suppressed. However, in this case, the bearing temperature was a high 130°C two hours after the start of the test. In Tests No. 3 to No. 5, if the volume A of the annular space S2 is 90% or more of the lubricant load and the volume B of the annular space S3 is 130% or more of the lubricant load, no lubricant leakage was measured, and the bearing temperature two hours after the start of the test was 55°C or lower. Therefore, it can be said that if the volume A of the annular space S2 is 90% or more of the lubricant load, the amount of lubricant to be sealed and the volume of the space in which the lubricant is sealed can be optimized, and lubricant leakage can be prevented even under high-speed rotation. It was also found that the temperature rise of the bearing can be suppressed. Therefore, if the volume B of the annular space S3 is 130% or more of the lubricant load, the amount of lubricant to be sealed and the volume of the space in which the lubricant is sealed can be optimized, and lubricant leakage can be prevented even under high-speed rotation. It was also found that the temperature rise of the bearing can be suppressed. In other words, if the volume A of the annular space S2 is 90% or more of the lubricant load, or the volume B of the annular space S3 is 130% or more of the lubricant load, then the amount of lubricant to be sealed and the volume of the space in which the lubricant is sealed can be optimized, lubricant leakage can be prevented under high-speed rotation, and the temperature rise of the bearing can be suppressed.

[0035] The configurations of the bearing device 1 and sealing devices 10, 10A, 10B, and 10C described above are not limited to those shown in the illustrations. For example, the bearing device 1 is not limited to a single row but may also be a double row. Furthermore, the shapes of the core material 11 and seal portion 17 that constitute the sealing devices 10, 10A, 10B, and 10C are not limited to the illustrated examples. In addition, although the above embodiment describes an example in which the sealing device 10 is attached to the outer member 2, the sealing device 10 may also be attached to the inner member 4, and although an example in which the inner member 4 rotates was described, the outer member 2 that constitutes the outer ring may also rotate. [Explanation of symbols]

[0036] 1. Bearing device 2 Outer ring (outer member) 2d Inner peripheral surface 4 Inner ring (inner member) 4b Outer peripheral surface 6 Rolling element 10, 10A, 10B, 10C Sealing device 10a Inner space 11 Core material 17 Sealing part S1 Sealed space S2, S3 Annular space

Claims

1. A sealing structure for a bearing device, which includes a sealing device for sealing the sealed space between an inner member and an outer member that rotate relatively coaxially, The sealing device, which is attached to either the inner member or the outer member, comprises an annular core material and an elastic sealing portion fixed to the core material and extending toward the other of the inner member and the outer member. The sealed space contains a lubricant and has rolling elements interposed so as to be rotatable. A sealing structure characterized in that the volume of the annular space formed in the inner space of the sealing device is 90% or more of the amount of lubricant loaded.

2. A sealing structure for a bearing device, which includes a sealing device for sealing the sealed space between an inner member and an outer member that rotate relatively coaxially, The sealing device, which is attached to either the inner member or the outer member, comprises an annular core material and an elastic sealing portion fixed to the core material and extending toward the other of the inner member and the outer member. The sealed space contains a lubricant and has rolling elements interposed so as to be rotatable. The sealing device is provided between the ends of the inner member and the outer member, A sealing structure characterized in that the volume of the annular space formed between the edge of the rolling element and the sealing device is 130% or more of the amount of lubricant loaded.

3. In claim 1 or claim 2, The core material comprises a cylindrical portion that is fitted into the one member, and a disc portion that is connected to one axial end of the cylindrical portion and extends radially from that end. The sealing portion comprises a bead portion that covers the outer circumferential surface of the cylindrical portion and a lip portion that covers the leading end of the disc portion in the extending direction and extends toward the other member. A sealing structure characterized in that the sealing portion is not disposed on either the side of the disc portion facing the sealed space or the side facing the external space.

4. In claim 1 or claim 2, The core material comprises a cylindrical portion that is fitted into the one member, and a disc portion that is connected to one axial end of the cylindrical portion and extends radially from that end. The sealing portion comprises a covering portion that covers the external space side of the disc portion and a lip portion that covers the leading end of the disc portion in the extending direction and extends toward the other member. The sealing structure is characterized in that the disc portion is provided with a recess.

5. In claim 1, The core material comprises a cylindrical portion that is fitted into the one member, and a disc portion that is connected to one axial end of the cylindrical portion and extends radially from that end. The sealing portion comprises a bead portion that covers the outer circumferential surface of the cylindrical portion and a lip portion that covers the leading end of the disc portion in the extending direction and extends toward the other member. The sealing structure is characterized in that the volume of the annular space is the entire area of ​​the inner space surrounded by the cylindrical portion, the disc portion, and the lip portion on the side of the space to be sealed.

6. In claim 1 or claim 2, The sealing portion is made of conductive rubber and includes a lip portion that slides against the other member. A sealing structure characterized in that the sealing device is configured as a conductive seal.

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