Bearing seal and use thereof

Abstract

A bearing sealing element (2) comprises a base part (21) and a sealing part (20), wherein the base part (21) can be fixedly assembled on a bearing outer ring (5), and the sealing part (20) and a flange (30) of a bearing inner ring (3) can form lubricating grease sealing. The sealing part (20) comprises a non-contact seal (24) capable of preventing lubricating grease in the bearing (1) from leaking outwards through clearance fit and a contact seal (25) located on the outer side of the non-contact seal (24) in the axial direction. In the assembled state, the sealing part (20) can be integrally contained in a roughly annular space (P) between the axial end part (41) of the bearing retainer (4) and the outer diameter surface (31) of the corresponding inner ring flange (30). On the basis of the sealing element, the invention further provides a rolling bearing (1), in particular a cylindrical roller bearing unit for the wheel end of a railway vehicle. Therefore, the bearing (1) obtains a good sealing effect, and the problem of leakage of internal lubricating grease can be thoroughly solved.

Description

TECHNICAL FIELD

[0001] The present invention relates to a bearing seal and to a rolling bearing, in particular a cylindrical roller bearing unit for a railway vehicle wheel axle, incorporating such a seal. BACKGROUND

[0002] Figure 1 A cross-sectional view of a cylindrical roller bearing unit as used in a railway vehicle is shown. As can be seen from the figure, the bearing unit 1 is composed of two single-row cylindrical roller bearings combined together, and on both axial sides, a seal 2 is provided to prevent both the ingress of foreign matter from the outside into the bearing interior and the leakage of lubricating grease from the bearing interior to the outside. Figure 2 is Figure 1 A close-up view of the area where the left-hand seal is located. It is clearly shown that the seal 2 is composed of a hard insert (typically a metal stamping) of generally C-shaped cross-section, comprising a base portion 21 which can be fixedly fitted on the outer ring 5 and a non-contact seal 22 which can form a clearance fit with the outer diameter surface 31 of the rib 30 of the inner ring 3. The non-contact seal 22 is formed by an axial extension (hereinafter still denoted by the numeral 22) of the hard insert at its radially free end, which is generally parallel to the outer diameter surface 31 of the inner ring rib 30, and between which a narrow clearance passage 23 is formed. Since lubricating grease generally has a certain viscosity, when the clearance passage 23 is sufficiently narrow (for example, less than 0.8 mm in radial dimension), the leakage of lubricating grease from the bearing interior to the outside can be prevented even by the non-contact seal.

[0003] However, in actual application, due to the changes in load and temperature, a small amount of lubricating grease will still overflow from the clearance passage 23 in the bearing interior. In particular, after a period of operation, the base oil of the lubricating grease itself will also be separated out. Since the base oil has a relatively low viscosity and good flowability, it is easy to seep out from the clearance. The above factors will all result in the leakage of lubricating grease, although in most cases the degree is not serious. Nevertheless, the leaked lubricating grease will on the one hand pollute the environment and on the other hand create a false appearance of bearing failure, causing inconvenience to the user in use and maintenance. Although there are many seals of good performance in the prior art, in the above-mentioned bearing unit, due to the excessively narrow radial spacing between the axial end of the cage and the outer diameter surface of the inner ring rib (typically not more than 6 mm), it is difficult to embed a common contact seal (for example, a sealing lip) therein, so it is impossible to solve the above-mentioned problem by using the prior art.

[0004] The reality calls for a bearing seal which can prevent the leakage of lubricating grease and at the same time can adapt to the narrow radial spacing between the cage and the rib. SUMMARY

[0005] To solve the above technical problems, the application provides a bearing seal, which comprises a base capable of being fixedly assembled on a bearing outer ring and a sealing part capable of forming a grease seal between a flange of a bearing inner ring. The sealing part comprises a non-contact seal capable of preventing the leakage of the bearing inner grease outward by means of a clearance fit and a contact seal located axially outside the non-contact seal. In the assembled state, the sealing part is accommodated in a substantially annular space between the axial end of the bearing cage and the outer diameter surface of the corresponding inner ring flange.

[0006] The above sealing part solves the problem of grease leakage of the non-contact seal by arranging the contact seal axially outside the non-contact seal. Moreover, the sealing part solves the practical problem that the sealing part cannot be embedded in the annular space between the axial end of the bearing cage and the outer diameter surface of the inner ring flange due to the too large radial size of the sealing part. The above solution fills the gap of the existing sealing part based on the flattening and small radial size design of the sealing part (especially the sealing lip). The improved sealing part can be directly applied to the existing products including railway bearings, and has high universality and application convenience.

[0007] Based on the above sealing part, the application further provides a rolling bearing. The bearing thus has good sealing effect and can completely solve the problem of grease leakage. BRIEF DESCRIPTION OF DRAWINGS

[0008] The various embodiments and beneficial technical effects of the application will be described in detail below in combination with the drawings.

[0009] Figure 1 shows a cross-sectional schematic view of an existing railway bearing unit;

[0010] Figure 2 shows Figure 1 shows a partial enlarged view of the area where the left sealing part in the middle is located;

[0011] Figure 3 shows a cross-sectional schematic view of an improved bearing seal assembled on a bearing; and

[0012] Figure 4 shows Figure 3 shows a partial enlarged view of the area where the sealing part is located in the middle. DETAILED DESCRIPTION

[0013] In the following description, the same or similar reference numerals are always used to designate the same or similar components. The terms indicating directions, such as "axial", "radial" and "circumferential", unless otherwise defined or specified, refer to the axial, radial and circumferential directions of the components being described. Furthermore, the terms "(bearing) inner side" and "(bearing) outer side" are based on the inner space of the bearing defined by the inner and outer rings of the bearing, and correspond to the inner and outer sides of the bearing in the axial direction, respectively. Figures 2 to 4

[0014] Figure 3 A cross-sectional view of the improved bearing seal mounted on a bearing is shown. Figure 4 A partial enlarged view of the sealing portion of the seal is further shown. As can be seen from the above view, the sealing portion 20 of the improved seal 2 is formed by an axial extension 22 of the hard insert at the radial free end thereof and a flexible material attached to the extension. The flexible material can be rubber or other elastomer material, typically such as nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) or fluoro rubber (FKM), etc., which is formed by molding and / or injection molding into a non-contact seal 24 capable of preventing the lubricating grease inside the bearing from leaking out through a gap fit and a contact seal 25 located axially outside the non-contact seal 24 for further preventing the lubricating grease from leaking out.

[0015] Unlike the non-contact seal (i.e. the axial extension of the hard insert) 22 described in the background art, the non-contact seal 24 formed of the flexible material is formed with a tooth-like structure 26 on the side of the outer diameter surface 31 facing the flange 30 of the inner ring, which prevents the lubricating grease from leaking out. As can be seen from the above view, the tooth-like structure 26 is formed by a plurality of circumferential grooves 27 each having a semicircular cross-section. Figure 4 As can be more clearly seen, the tooth-like structure 26 comprises three circumferential grooves each having a semicircular cross-section. Of course, the grooves can also have other geometric shapes, such as triangular, rectangular or trapezoidal. The number of grooves can also be 1-2 or more than 4. Furthermore, the radial (gap) dimension g of the gap passage 23 is set to be between 0.14-0.68 mm, preferably between 0.25-0.50 mm.

[0016] In the illustrated embodiment, the contact seal 25 comprises at least one contact seal lip (hereinafter still denoted by the numeral 25). In order to reduce the temperature rise caused by friction, the seal lip 25 is preferably lubricated with low-friction grease, a portion of which is filled in the grease storage space S at the time of delivery (see the description below). Furthermore, the seal lip 25 is configured to form a contact pressure of 4-30 Newton / meter (i.e. on a contact track of one meter in length) between the outer diameter surface 31 of the flange 30 of the inner ring in the mounted state. In the preferred case, the contact pressure of the seal lip 25 is set to be between 4-14 Newton / meter.

[0017] ​The sealing lip with the above contact pressure can prevent the leakage of lubricating grease and will not cause severe temperature rise due to excessive friction. In the high-speed running simulation test at 1200 rpm, the overall temperature of the bearing caused by the friction of the sealing lip is not more than 70°C. In addition, the sealing lip with the above contact pressure also has a good pressure release mechanism. When the internal pressure of the bearing rises, the sealing lip is easy to open due to the small contact pressure, thereby easily releasing the internal pressure of the bearing, avoiding the accumulation of high pressure to trigger the breakthrough leakage of the sealing lip.

[0018] To obtain the above performance, the sealing lip 25 is designed with a lip thickness (t) of 0.2-1.0 mm, an axial angle (θ) of 20-40°, and an interference (δ) of 0.2-1.2 mm between the outer diameter surface. In a preferred case, the sealing lip 25 can have a lip thickness of 0.4±0.1 mm, an axial angle of 25-35°, and an interference of 0.3-0.9 mm between the outer diameter surface. It is not difficult to understand that smaller lip thickness and smaller interference result in smaller contact pressure of the sealing lip. Moreover, in the case of limited radial space for the length of the sealing lip, smaller axial angle also allows longer sealing lip to be built. As described before, in the case of the same internal and external pressure difference of the bearing, the longer sealing lip is easy to open due to the larger pressure it bears, thus easily releasing the internal pressure of the bearing.

[0019] In the illustrated embodiment, the sealing lip 25 extends in the axial direction towards the outside of the bearing (left side in the figure), thereby forming a lubricating grease storage space S with the non-contact seal 24. It is noted that the lubricating grease used by the seal is not the same in kind as that used by the bearing, but the use of the former is conducive to blocking the overflow of the latter. As a preferred embodiment, the seal 2 can also form a protrusion 27 on the radial outside of the sealing part 20, which protrudes in the axial direction towards the outside of the bearing, for the lubricating grease rolled by the rolling body to converge to both sides of the bearing, which is conducive to avoiding the overflow of these lubricating greases from the gap channel 23 of the non-contact seal 24.

[0020] As a preferred embodiment, the sealing portion 20 can be formed in a flat structure. After assembly, its maximum radial dimension (the maximum height beyond the outer diameter surface 31) H is no more than 4 mm, so as to form a sufficient (2 mm or more) safety distance between the axial end portion 41 of the radially outer side (upper side in the figure) retainer 4. The above design is to ensure that the sealing portion 20 can be fitted in the radially narrow annular space P without interfering with the radially outer side retainer 4 during assembly and operation, and thus is particularly suitable for cylindrical roller bearing units of the following boundary sizes: the inner diameter d = 120 mm, the outer diameter D = 215 mm or 220 mm; or, the inner diameter d = 130 mm, the outer diameter D = 240 mm, etc. The cylindrical roller bearing units of the above boundary sizes are mainly applied to the wheel end of the railway vehicle, and belong to the non-ISO standard bearing series. Since the radial dimension of the annular space P is no more than 6 mm, and the axial dimension is only 12.3 mm, it is difficult to find a suitable existing seal. In a further preferred case, the radial height H of the sealing portion 20 can be set to be between 3-4 mm.

[0021] As a further preferred embodiment, the aspect ratio L / H between the axial dimension L and the radial dimension H of the sealing portion 20 can be constructed to be between 1.5:1-2.5:1. Here, the axial dimension L is defined as the total coverage in the axial direction of both the contact seal (seal lip) 25 and the non-contact seal 24 after assembly, as indicated in the figure. The above ratio not only facilitates the sealing portion 20 to fit into the radially narrow annular space P, but also allows the seal lip 25 and the non-contact seal 24 to each have sufficient axial space. The sufficient axial space allows the non-contact seal 24 to adopt a longer gap passage 23, thereby improving the sealing effect on the bearing internal grease, and also allows the seal lip 25 to adopt a smaller axial included angle (θ), thereby obtaining a smaller contact pressure and opening pressure. In addition, the sealing portion 20 of the above ratio also allows the seal lip 25 and the non-contact seal 24 to form a grease storage space S with sufficient capacity. In summary, the flat structure of the above ratio is conducive to constructing a sealing portion 20 with optimal performance in the radially narrow annular space P.

[0022] As can be seen from the above description, the improved seal can be used to directly replace the original seal of the bearing without changing the existing structure of the bearing, and thus has great universality and application convenience. It is not difficult to understand that the above seal is also applicable to other types of rolling bearings, including but not limited to tapered roller bearings and various ball bearings, which are limited by the narrow radial spacing between the retainer and the inner ring rib.

[0023] It should be noted that the structure, process and error of the sealing part have significant influence on its performance due to the complex material properties of the flexible material such as rubber. The structural features and parameter ranges of the sealing part are obtained by repeated design, simulation and test of the inventors, and cannot be easily obtained by theory, experience and imagination.

[0024] The bearing sealing part and its application described above are not limited by the specific embodiments, and the more general technical solutions will be limited by the appended claims. Any changes and improvements of the present application, as long as they meet the limitations of the appended claims, belong to the protection scope of the present application.

Claims

1. A bearing seal (2) comprising a base (21) which can be fixedly fitted on a bearing outer ring (5) and a sealing portion (20) which can form a grease seal with a rib (30) of a bearing inner ring (3), the sealing portion (20) comprising a non-contact seal (24) which can prevent the outward leakage of grease in the bearing (1) by a clearance fit and a contact seal (25) which is located axially outside the non-contact seal (24), characterized in that: In the assembled state, the seal portion (20) is housed in its entirety in a substantially annular space (P) between the axial end (41) of the bearing cage (4) and the outer diameter face (31) of the corresponding inner ring rib (30).

2. The bearing seal (2) of claim 1, wherein: In the assembled state, the maximum radial dimension H of the seal portion (20) is not more than 4 mm.

3. The bearing seal (2) of claim 2, wherein: The seal portion (20) is formed by an axially extending portion (22) of hard insert and a flexible material attached to the extending portion (22) to form the contact seal (24) and the non-contact seal (25), the aspect ratio L / H between the axial dimension L and the radial dimension H of the seal portion (20) being between 1.5 and 2.

5.

4. The bearing seal (2) of claim 3, wherein: The contact seal (25) comprises at least one seal lip which, in the assembled state, forms a contact pressure of 4 to 30 N / m with the outer diameter face (31).

5. The bearing seal (2) as set forth in claim 4, characterized in that: The seal lip (25) is made of nitrile rubber, hydrogenated nitrile rubber or fluororubber, forms an angle (θ) of 20 to 40° with the axial direction, has a lip thickness (t) of 0.2 to 1.0 mm and forms a clearance (δ) of 0.2 to 1.2 mm with the outer diameter face (31).

6. Bearing seal (2) according to any one of claims 1 to 5, characterized in that The non-contact seal (24) forms a toothed structure (26) on the side facing the outer diameter face (31) for preventing leakage of lubricating grease.

7. The bearing seal (2) as set forth in claim 6, characterized in that: The bearing seal (2) forms a protrusion (27) on the radially outer side of the seal portion (20) which protrudes axially to the outside of the bearing.

8. The bearing seal (2) of claim 6, wherein: The seal lip (25) extends towards the outside of the bearing (1) and forms a lubricating grease storage space (S) with the non-contact seal (24).

9. A rolling bearing (1) comprising a bearing seal (2) according to any one of the preceding claims.

10. Rolling bearing (1) according to claim 9, characterized in that: The rolling bearing (1) is a cylindrical roller bearing unit. The rolling bearing (1) is a cylindrical roller bearing unit.

Images