Oil seal, and rolling bearing device for rolling stock axle

Abstract

An oil seal 54 that seals a rolling bearing 1 for a rolling stock axle is provided with: a core 541; a lip part 542 which is integrated with the core 541 and comprises an elastic material; and an elastic member 543. The lip part 542 is provided with: a base part 542a covering the inner diameter end of the core 541; a main lip 542b extending from the base part 542a toward the bearing inner side; and a dust lip 542c that is, compared to the main lip 542b, located closer to the bearing outer side. The elastic member 543 applies tension to the main lip 542b. The total tension of the oil seal 54 is set to be 12 N or less.

Description

Oil seal and rolling bearing device for railway vehicle axles

[0001] The present invention relates to an oil seal and a rolling bearing device for a railway vehicle axle provided with the oil seal.

[0002] A rolling bearing for a railway vehicle axle that rotatably supports the axle of a railway vehicle includes an outer ring having a raceway surface on its inner circumference, an inner ring having a raceway surface on its outer circumference, rolling elements disposed between the raceway surface of the outer ring and the raceway surface of the inner ring, and a seal device that seals the space between the outer ring and the inner ring on both axial sides. The rolling elements are arranged in multiple rows. The seal device has a configuration in which a seal lip of an oil seal fixed to the inner circumferential surface of the outer ring is brought into contact with the outer circumferential surface of a member called an oil drain or a rear cover fixed to the axle.

[0003] In order to achieve both the sealing performance and low torque performance of the seal device, a rolling bearing device for railway vehicles is known in which a hard carbon coating is formed on a portion of the seal lip of the oil seal that slidably contacts the outer circumferential surface of the oil drain (Patent Document 1).

[0004] Japanese Unexamined Patent Application Publication No. 2006 - 275231

[0005] In order to achieve carbon neutrality, it is required to further reduce torque while ensuring the required sealing performance. In addition, for the purpose of alleviating traffic congestion, in recent years, the construction of railway networks has been progressing in Southeast Asia and other regions. In such a rolling bearing device for railway vehicle axles used in a harsh environment of high temperature and high humidity, it is necessary to suppress lubrication failure due to the intrusion of foreign matter and the deterioration of grease through low heat generation as much as possible. The technology described in Patent Document 1 cannot sufficiently meet such requirements.

[0006] Therefore, an object of the present invention is to provide an oil seal and a rolling bearing device for a railway vehicle axle that can achieve low torque and low heat generation while ensuring the required sealing performance.

[0007] To achieve the above objectives, the present invention provides an oil seal for sealing a rolling bearing for a railway vehicle axle, comprising a core metal, a lip portion made of an elastic material integrated with the core metal, and an elastic member, wherein the lip portion comprises a base portion covering the inner diameter end of the core metal, a first lip extending from the base portion toward one side, and a second lip located toward the other side of the first lip, and the elastic member provides tension to the first lip, characterized in that the total tension is 12 N or less.

[0008] By setting the total tension force to 12N or less, a reduction in torque can be achieved. This reduces the energy consumption of railway vehicles during operation. Furthermore, since less heat is generated, the lifespan of the oil seal is improved even when used in harsh environments such as high temperature and humidity, and the deterioration of the grease due to oxidation, oil separation, and softening can be suppressed.

[0009] It is preferable to set t / L to 0.10 or more and 0.35 or less, where t is the thickness of the base portion of the first lip, and L is the distance between the center of the elastic member and the end face on one side of the base portion.

[0010] If t / L is less than 0.10, the rigidity of the base of the first lip decreases, so even if the tension force is reduced, the first lip may excessively elastically deform, and the tip of the first lip may come into contact with the outer surface of the sliding member. Such contact can lead to torque loss and increased heat generation. Also, if t / L exceeds 0.35, the rigidity of the base of the first lip is too high, resulting in an excessive tension force of the first lip, making it difficult to achieve a total tension force of 12N or less.

[0011] The wall thickness t at the base of the first lip can be 1.0 mm or less. If the wall thickness t exceeds 1.0 mm, the rigidity of the first lip becomes excessive, making it difficult to obtain a total tightening force of 12 N or less for the oil seal.

[0012] The tension of the elastic member can be set to 7N or less. This makes it easy to set the total tension of the oil seal to 12N or less.

[0013] As the elastic material forming the lip portion, a material with a hardness of 70 ± 10 on a Type A durometer conforming to JIS K6253 can be used. If the hardness exceeds 80, it will negatively affect the sealing performance of the oil seal, and if the hardness falls below 60, the wear resistance of the oil seal will be insufficient.

[0014] A rolling bearing device for a railway vehicle axle can be constructed using the oil seal described above, an outer ring having a raceway surface on its inner circumference, an inner ring having a raceway surface on its outer circumference, a plurality of rolling elements arranged between the raceway surfaces of the outer ring and the inner ring, a cage that holds the rolling elements at equal intervals in the circumferential direction, and a sliding contact member attached to the axle that slides against the first lip and the second lip of the oil seal.

[0015] In this rolling bearing device for railway vehicle axles, a metal member attached to the outer ring of the rolling bearing for railway vehicle axles via a seal case can be positioned on one side of the first lip of the oil seal.

[0016] In this rolling bearing device for railway vehicle axles, a vent connected to the space inside the bearing can be provided on the outer ring.

[0017] According to the present invention, it is possible to achieve low torque and low heat generation while ensuring the required sealing performance. This reduces energy consumption and extends the maintenance cycle by suppressing the deterioration of oil seals and grease.

[0018] This is an axial cross-sectional view of a rolling bearing device for a railway vehicle axle according to this embodiment. This is an enlarged cross-sectional view of the seal device. This is a diagram showing the results of the bearing durability test. This is a diagram showing the results of the heat generation test of the oil seal alone. This is a table showing the results of the dust resistance test, water resistance test, and grease leakage resistance test.

[0019] The embodiments for carrying out the present invention will be described below with reference to the drawings.

[0020] Figure 1 shows a rolling bearing device for a railway vehicle axle according to an embodiment of the present invention. This bearing device comprises a rolling bearing 1 for a railway vehicle axle (hereinafter simply referred to as "bearing") and a sealing device 50. In this embodiment, a double-row tapered roller bearing is exemplified as the bearing 1. The bearing 1 comprises an outer ring 10, two inner rings 20 arranged in the axial direction, a plurality of tapered rollers 30 as rolling elements, and a cage 40. The outer ring 10 has a double-row conical raceway surface 12 formed on its inner circumferential surface, and the inner rings 20 have a single-row conical raceway surface 22 formed on its outer circumferential surface.

[0021] By arranging the smaller diameter ends of the two inner rings 20 together, a double-row raceway surface 22 is formed. In addition to arranging the smaller diameter ends of the inner rings 20 together directly, spacers may be placed between the smaller diameter ends. Tapered rollers 30, which act as rolling elements, are arranged between the raceway surface 12 of the outer ring 10 and the raceway surface 22 of the inner ring 20. Corresponding to the arrangement of the raceway surfaces 12 and 22 in double rows, the tapered rollers 30 are also arranged in double rows. The cage 40 holds the tapered rollers 30 in each row at equal intervals in the circumferential direction. A lubricant such as grease is sealed in the space formed between the outer ring 10 and the inner ring 20 (the space inside the bearing), and this space is sealed by a sealing device 50 at both axial ends of the bearing 1. Hereinafter, in the axial direction, this space side will be referred to as the bearing interior side, and the opposite side will be referred to as the bearing exterior side.

[0022] The outer ring 10 is press-fitted and fixed to the inner circumferential surface of the axle box (not shown) of the railway vehicle. The outer ring 10 is provided with a vent 101 connected to the space inside the bearing, and when the internal pressure in the space inside the bearing rises, exhaust is carried out to the outside of the bearing through the vent 101. The vent may be omitted if not necessary.

[0023] Sliding contact members 61 and 62 are positioned on the bearing outer sides of the two inner rings 20, respectively. In this embodiment, the sliding contact member 61 on one axial side is called the oil drainer, and the sliding contact member 62 on the other axial side is called the rear cover. A cover member 64 is fixed to the shaft end of the axle 2 with bolts 66, and the oil drainer 61, inner rings 20, and rear cover 62, which are press-fitted onto the axle 2, are positioned between the cover member 64 and the shoulder portion 201 of the axle 2. By screwing in the bolts 66, the axial positioning of the oil drainer 61, inner rings 20, and rear cover 62 sandwiched between the cover member 64 and the shoulder portion 201 of the axle 2 is achieved.

[0024] Each of the axial sealing devices 50 comprises a seal case 52 attached to the outer ring 10, an oil seal 54, a metal ring 55 with an L-shaped cross-section as a metal member, and sliding contact members 61 and 62. In the sealing device 50 on one axial side, the oil drain 61 acts as the sliding contact member, and in the sealing device 50 on the other axial side, the rear cover 62 acts as the sliding contact member. The inner ends of both seal cases 52 on the bearing side are press-fitted and fixed to the inner circumferential surfaces of both axial ends of the outer ring 10. The outer ends of the two seal cases 52 on the bearing side are inserted into recesses 62a formed on the end faces of the sliding contact members 61 and 62, respectively, to form a non-contact seal.

[0025] Metal rings 55 are attached to the inner circumference of each seal case 52, and oil seals 54 are attached to the inner circumference of each metal ring 55. In this way, the oil seals 54 and metal rings 55 are fixed to the outer ring 10 via the seal cases 52. The inner diameter ends of both metal rings 55 are close to the outer circumferential surfaces of the sliding contact members 61 and 62, forming a non-contact seal between them and the sliding contact members 61 and 62. The metal rings 55 have the function of preventing grease leakage caused by lubricants such as grease filling the internal space of the bearing 1 being directly pushed onto the oil seals 54.

[0026] The structure of the oil seal 54 will be described in detail below based on Figure 2. Since the configuration of the oil seals 54 located on both axial sides of the bearing 1 is the same, the following description will only cover the oil seal 54 on the other axial side (right side in Figure 1), and the description of the oil seal 54 on the one axial side (left side in Figure 1) will be omitted.

[0027] As shown in Figure 2, the oil seal 54 comprises a core metal 541, a lip portion 542 integrated with the core metal 541, and a garter spring 543 as an elastic member. The core metal 541, the lip portion 542, and the garter spring 543 are all formed in annular shape.

[0028] The lip portion 542 is formed of an elastic material, such as a rubber material like nitrile rubber, acrylic rubber, or fluororubber. This lip portion 542 is integrated with the core metal 541 by means of, for example, vulcanization bonding. The lip portion 542 can also be formed of resin. The hardness of the elastic material forming the lip portion 542 is preferably 70 ± 10 on a Type A durometer (Shore hardness) according to JIS K6253. If the hardness is too high, it will negatively affect the sealing performance, and if the hardness is too low, the wear resistance will be insufficient.

[0029] The lip portion 542 integrally comprises a base portion 542a that covers the inner diameter end of the mandrel 541, a main lip 542b (first lip) extending from the base portion 542a toward one axial side (inside the bearing), and a dust lip 542c (second lip) extending from the base portion 542a toward the other axial side (outside the bearing). In this embodiment, the base portion 542a is formed to cover both the front and back sides of an inclined portion 541a provided at the inner diameter end of the mandrel 541, which is inclined so that it is displaced toward one axial side as it moves toward the inner diameter. End faces 542a1 and 542a2 extending in the radial direction are formed on both axial sides of the base portion 542a. Of these, the main lip 542b protrudes from the inner diameter side of the end face 542a1 on the inside side of the bearing, and the dust lip 542c protrudes from the inner diameter side of the end face 542a2 on the outside side of the bearing.

[0030] The main lip 542b and the dust lip 542c are both in contact with the outer circumferential surface (sliding surface) of the rear cover 62 with an overlap (see Figure 1). A garter spring 543 is attached to the outer circumferential surface of the tip of the main lip 542b, and the elastic force of this garter spring 543 in the diameter-reducing direction acts as an inward pressing force on the tip of the main lip 542b. This pressing force, the overlap given to the main lip 542b and the dust lip 542c, and the deflection reaction force at the base of both lips 542b and 542c create a tensioning force. The sum of the tensioning forces applied from the main lip 542b and the dust lip 542c to the sliding contact member (rear cover 62 in this embodiment) is called the total tensioning force. The total tensioning force can be measured, for example, using a tensioning force measuring instrument MTF1-100NA from Showa Sokki Co., Ltd.

[0031] In this invention, the total tightening force of the oil seal 54 is set to 12N or less. This enables a reduction in torque, thereby reducing energy consumption during the operation of railway vehicles. Furthermore, since low heat generation is achieved, the lifespan of the oil seal is improved even when used in harsh environments such as high temperature and humidity, and deterioration of the grease due to oxidation, oil separation, and softening can be suppressed. As a result, the maintenance cycle can be extended, and vehicle maintenance costs can be reduced.

[0032] While reducing the total tightening force of the oil seal 54 in this way raises concerns about a significant decrease in sealing performance, it was found that even when the total tightening force is 12N or less, the sealing performance does not decrease drastically, and the seal does not immediately become unusable due to insufficient sealing. However, if the total tightening force is excessively low, a significant decrease in sealing performance is unavoidable, so it is desirable to set the total tightening force to 6N or higher.

[0033] If the rigidity of the base of the main lip 542b is too low, even if the tensioning force is reduced, the main lip 542b may excessively elastically deform, and the tip of the main lip 542b may come into contact with the outer circumferential surface of the rear cover 62. Such contact can lead to torque loss and increased heat generation. From this viewpoint, it is preferable to set the ratio of t to L, t / L, shown in Figure 2, to 0.10 or more (t / L ≥ 0.10). t represents the wall thickness of the base of the main lip 542b, and L represents the length of the arm of the main lip 542b, specifically the axial distance between the corner portion 542b1 at the tip of the main lip 542b and the end face 542a1 on the bearing side of the base portion 542a. The base of the main lip 542b can be defined as the contact point between the rounded portion formed between the end face 542a1 on the bearing side of the base portion 542a and the outer circumferential surface of the main lip 542b and the flat outer circumferential surface of the main lip 542b. At this base, the thickness of the main lip 542b in the direction perpendicular to the flat outer surface of the main lip 542b becomes the thickness t of the main lip 542b.

[0034] On the other hand, if the rigidity of the base of the main lip 542b is too high, the tension of the main lip 542b becomes excessive, making it difficult to achieve a total tension of 12N or less. From this viewpoint, the ratio of t to L, t / L, described above is set to 0.35 or less, preferably 0.25 or less, and more preferably 0.18 or less (t / L ≤ 0.35, preferably t / L ≤ 0.25, more preferably t / L ≤ 0.18).

[0035] Furthermore, if the wall thickness t at the base of the main lip 542b is too large, the rigidity of the main lip becomes excessive, making it difficult to obtain a total tightening force of 12N or less for the oil seal 54. From this viewpoint, it is preferable that the wall thickness t be 1.0 mm or less. However, if the value of t is too small, it becomes difficult to mold the lip portion 542, so it is preferable that the wall thickness t be 0.5 mm or more.

[0036] In order to keep the total tightening force of the oil seal 54 below 12N, it is preferable to set the tightening force of the garter spring 543 alone to 7N or less.

[0037] Figure 3 shows the results of a bearing durability test in which the oil seal 54 of the embodiment and the oil seal of the comparative example were assembled into the same bearing 1. For the oil seal of the embodiment, the total tension force was F and the tension force of the garter spring 543 alone was f, with F = 10N, t / L = 0.14, t = 0.7 mm, and f = 6N. For the oil seal of the comparative example, the total tension force was F = 17N, t / L = 0.20, t = 0.7 mm, and f = 7N. In addition, the lip portion 542 of both the embodiment and the comparative example is formed of nitrile rubber with a hardness of 70 points on a Type A durometer conforming to JIS K6253.

[0038] As is clear from Figure 3, the bearing device using the oil seal 54 of the embodiment generated less heat throughout the entire operating period compared to the bearing device using the oil seal of the comparative example, and it was found that the amount of heat generated could be reduced by about 10%.

[0039] Figure 4 shows the results of a heat generation test conducted on the oil seals alone for the above-described examples and comparative examples. As is clear from Figure 4, the oil seals of the examples generated less heat throughout the entire operating period compared to the oil seals of the comparative examples, and it was found that the amount of heat generated could be reduced by about 15%.

[0040] Figure 5 shows the results of dust resistance and water resistance tests for the oil seals alone, as well as grease leakage resistance tests for the bearing devices, for the above-described examples and comparative examples. In the figure, "○" indicates particularly excellent performance, and "-" indicates no problems.

[0041] As is clear from Figure 5, the oil seal 54 of the embodiment was found to have the same sealing performance as the oil seal of the comparative example.

[0042] From these results, it became clear that this embodiment provides the same level of sealing performance as the comparative example while generating less heat than the comparative example.

[0043] In the above explanation, we have illustrated the case where a vent 101 for releasing excess internal pressure in the space inside the bearing is provided on the outer ring 10 of the bearing 1. However, this vent can also be provided on the oil seal 54 (for example, the core metal 541).

[0044] Also, in the above description, as the rolling bearing 1 for a railway vehicle axle, a tapered roller bearing using tapered rollers as rolling elements 30 was cited, but as the bearing 1, a deep groove ball bearing or a cylindrical roller bearing can also be used.

[0045] 1 Rolling bearing for railway vehicle axle 10 Outer ring 12 Raceway surface 20 Inner ring 22 Raceway surface 30 Tapered roller (rolling element) 40 Cage 52 Seal case 54 Oil seal 55 Metal member (metal ring) 61 Sliding contact member (oil drain) 62 Sliding contact member (rear cover) 541 Core metal 542 Lip portion 542a Base portion 542b Main lip (first lip) 542c Dust lip (second lip) 543 Garter spring (elastic member)

Claims

1. An oil seal for sealing a rolling bearing for a railway vehicle axle, comprising a core metal, a lip portion made of an elastic material integrated with the core metal, and an elastic member, wherein the lip portion comprises a base portion covering the inner diameter end of the core metal, a first lip extending from the base portion toward one side, and a second lip located toward the other side of the first lip, and the elastic member provides tension to the first lip, characterized in that the total tension is 12 N or less.

2. The oil seal according to claim 1, wherein the thickness of the base portion of the first lip is t, and the distance between the center of the elastic member and the end face on one side of the base portion is L, and t / L is 0.10 or more and 0.35 or less.

3. The oil seal according to claim 1, wherein the wall thickness t of the base portion of the first lip is 1.0 mm or less.

4. The oil seal according to claim 1, wherein the tension force of the elastic member is 7 N or less.

5. The oil seal according to claim 1, wherein the elastic material forming the lip portion has a hardness of 70 ± 10 on a Type A durometer compliant with JIS K6253.

6. A rolling bearing device for a railway vehicle axle, comprising an oil seal according to any one of claims 1 to 5, an outer ring having a raceway surface on its inner circumference, an inner ring having a raceway surface on its outer circumference, a plurality of rolling elements disposed between the raceway surface of the outer ring and the raceway surface of the inner ring, a cage that holds the rolling elements at equal intervals in the circumferential direction, and a sliding contact member attached to the axle and slidingly contacting the first lip and the second lip of the oil seal.

7. A rolling bearing device for a railway vehicle axle according to claim 6, wherein a metal member attached to the outer ring of the rolling bearing for the railway vehicle axle via a seal case is positioned on one side of the first lip of the oil seal.

8. The rolling bearing device for a railway vehicle axle according to claim 6, wherein the outer ring is provided with a vent connected to the space inside the bearing.

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