Bearing

Abstract: There is provided a bearing sealing device capable of substantially completely preventing a leak of grease. A taper end portion (18) of an axial extension (16) of the bearing sealing device has an opposite surface (20) and a rake face (21) that forms a specified rake angle with the opposite surface (20). The opposite surface (20) forms a narrow passage (19) between the opposite surface (20) and an outer peripheral surface (2A) of an inner ring (2). The narrow passage (19) allows air to pass easily, but it allows grease to hardly pass therethrough. Further, the axial extension (16) includes part (11A) of a core metal (11) that extends axially and has its foremost end (11A-1) located axially inside an axial outermost end (2A-1) of the outer peripheral surface (2A) of the inner ring (2). Grease moving axially outwardly on the outer peripheral surface (2A) is moved along the rake face (21) of the taper end portion (18) and then guided along a cover portion (15) of the bearing sealing device to an outer ring (1). The part (11A) of the core metal (11) prevents the axial extension (16) from being bent radially outwardly by a centrifugal force.

Description: The present invention relates to a bearing having a sealing device, in particular outer ring rotating type bearings such as bearings for axles, and bearings for engine accessories like outer ring rotating type water pumps, idlers and tensioners. Conventionally, as a bearing sealing device for this type of bearing, there is one as shown in Fig. 4. The sealing device includes a main lip 73 that is put in slidable contact with a side surface 72A located axially outwardly of an annular groove 72 formed on an outer peripheral surface 71A of an inner ring 71, and an auxiliary lip 75 provided with interposition of a specified clearance to a slant side surface 72B arranged opposite to the side surface 72A. The main lip 73 and the auxiliary lip 75 are converged at their roots to be integrated into one body, and a radially outward end portion (not shown) thereof is fixed to an outer ring (not shown). In the sealing device, the auxiliary lip 75 intercepts grease from inside the bearing. Further, the grease that has passed around the auxiliary lip 75 is intercepted by the main lip 73. However, in the above prior art bearing sealing device, a pressure force exerted from the main lip 73 on the side surface 72A is sometimes weakened by a centrifugal force depending on use conditions, and therefore the grease that has passed around the auxiliary lip 75 possibly passes around the main lip 73. The above also results in the problem that the leak of the grease is incompletely prevented. US 4,655,617 and US 4,830,518 both show bearings having the features illustrated in Fig. 4. The sealing device providing the main and auxiliary sealing lips is however stiffened by having a core metal in the main body of the device from which the lips project (US 4,655,617) or the main body and the auxiliary lip (US 4,830,518). US 4,655,617 also shows an example of a metal sealing device but this can only provide a non-contacting sealing lip analogous to the auxiliary sealing lip. These sealing devices are, however, relatively cumbersome and their presence results in a considerable increase in the overall size of the bearings. The object of the present invention is therefore to provide a bearing sealing device and a bearing sealing mechanism capable of substantially completely preventing the leak of grease. The present invention provides a bearing comprising a bearing sealing device provided between an outer ring and an inner ring of the bearing in which the outer ring rotates, said device sealing a space between the outer ring and the inner ring and being securely fixed to the outer ring so as to rotate together with the outer ring, the sealing device including a portion fixed to the outer ring, a cover portion which extends radially inwardly of the outer ring from the fixed portion and covers the space between the outer ring and the inner ring, and an axial extension which is made of an elastic material and extends in an axially inward direction from the cover portion, wherein the axial extension includes a taper end portion having a surface which is opposed to an outer peripheral surface of the inner ring and forms between said opposing surface and the outer peripheral surface a narrow passage having a width such that air is allowed to pass comparatively easily and oil is allowed to pass only with comparative difficulty, and a rake face at an oblique angle to said opposing surfaces, a core metal extending through the fixed portion and the cover portion respectively, and a retainer which holds rolling members of the bearing being arranged between the outer ring and the inner ring axially inwardly with respect to the axial extension, and wherein the axial extension extends axially inwardly beyond an axially outer surface of the retainer such that the axial extension overlaps the retainer, the core metal projects axially inwardly from the cover portion through the axial extension up to a position on a radially outer side of the outer peripheral surface of the inner ring, where a foremost end of the core metal is located in the vicinity of the taper end portion; and the retainer has a slant surface radially outwardly of an inner circumferential surface of the retainer such that the distance between the retainer and the rake face of the taper end portion of the axial extension is set larger than the distance between the retainer and the outer peripheral surface of the inner ring. The present inventor and others have confirmed through experiment that, when the balls are rotating while rolling between the outer ring and the inner ring, a lubricating oil circulates in a route of (balls) → (a space between the outer peripheral surface of the inner ring and the retainer) → (a space between the rake face of the taper end portion of the axial extension and the retainer) → (a space between the cover portion and the retainer) → (a space between the retainer and the outer ring) → (balls). Then, with the distance L1 between the retainer and the rake face of the taper end portion set greater than a distance L2 (L1 > L2) between the retainer and the outer peripheral surface of the inner ring in accordance with the present invention, the lubricating oil path through the space between the rake face of the taper end portion of the axial extension and the retainer is made larger than the lubricating oil path through the space between the outer peripheral surface of the inner ring and the retainer. With this arrangement, the lubricating oil from the space between the outer peripheral surface of the inner ring and the retainer is guided to the space between the rake face of the taper end portion of the axial extension and the retainer, and it hardly penetrates into the space between the inner ring and the taper end portion. Therefore, in cooperation with the sealing effect produced by the narrow passage formed between the taper end portion and the outer peripheral surface of the bearing inner ring, the possible leak of the lubricating oil is more surely prevented. Furthermore, as the core metal projects through the axial extension and the foremost end of the core metal is located axially in the vicinity of the taper end portion, the axial extension is prevented from being bent radially outwardly by centrifugal force or another external force generated when the outer ring is rotated. Therefore, even when a centrifugal force is generated due to the rotation of the outer ring, the possible leak of the grease can be prevented substantially completely. Moreover, by virtue of the presence of the core metal, the clearance between the axial extension and the outer peripheral surface of the inner ring can be set with high accuracy. In a bearing sealing mechanism according to the invention the taper end portion can have at its axially innermost end a recess portion that is recessed radially outwardly from the opposing surface that forms the narrow passage and is recessed axially outwardly from the foremost end of the rake face. With the above arrangement, grease that has axially moved along the outer peripheral surface of the inner ring and reached the taper end portion is firstly caught in the recess portion at the axially innermost end. Then, the mass of the grease is retained in the recess portion. Therefore, an oil component of the grease is intercepted by the mass of grease, so that the oil component of the grease is prevented from entering the narrow passage. In a further, advantageous feature of the invention, the axial extension has a recess portion that is located axially outwardly with respect to the taper end portion and is recessed radially outwardly with respect to the opposite surface of the taper end portion. With this arrangement, the grease that has accidentally passed around the taper end portion is caught in the recess portion. Therefore, the possible leak of the grease is more surely prevented. Preferably, that part of the core metal in the axial extension has an annular configuration and exists continuously around an entire peripheral surface of the inner ring, so increasing the resistance of the axial extension to being bent radially outwardly by the centrifugal force throughout the entire peripheral surface. Therefore, even when a centrifugal force is generated due to the rotation of the outer ring, the possible leak of the grease may still be prevented substantially completely. In one embodiment of the invention, there is provided a crown-shaped retainer that is made of resin and holds rolling members arranged between the outer ring and the inner ring. The retainer has a projection including a surface that is opposed to the outer peripheral surface of the inner ring axially inwardly with respect to the taper end portion, and forms with the outer peripheral surface of the inner ring a further narrow passage having such a specified narrowness that air is allowed to easily pass and oil is allowed to hardly pass. Such a projection can intercept the grease in advance of the taper end portion and so more surely prevent the possible leak of the grease. The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: Fig. 1A is a sectional view of a bearing sealing device according to a first embodiment of the present invention; Fig. 1B is a sectional view of an essential part of a modification embodiment of the first embodiment; Fig. 1C is a sectional view of an essential part of another modification embodiment of the first embodiment; Fig. 2 is a fragmentary sectional view of a second embodiment of the present invention; Fig. 3 is a sectional view of a third embodiment of the present invention; and Fig. 4 is a view showing the structure of a prior art bearing sealing device. The present invention will be described in detail below based on embodiments thereof with reference to the accompanying drawings. First Embodiment Fig. 1A shows a bearing sealing device according to a first embodiment of the present invention. This bearing sealing device is arranged between an outer ring 1 and an inner ring 2 of a bearing in which the outer ring 1 rotates, and seals a space between the outer ring 1 and the inner ring 2. The bearing has a plurality of balls 3 arranged in a circular ring form between the outer ring 1 and the inner ring 2. To the plurality of balls 3 is fitted a crown-shaped plastic retainer 5W. The first embodiment has a sectionally bracket-shaped core metal 11 and an elastic portion 12 that is formed of an elastic material and fixed tightly to the core metal 11. The first embodiment includes a fixed portion 13 fit in and secured to a recess 4 at an axial end portion formed on an inner peripheral surface 1A of the outer ring 1, and a cover portion 15 that extends radially inwardly from the fixed portion 13 and covers a space between the outer ring 1 and the inner ring 2. The first embodiment further includes an axial extension 16 that extends axially inwardly from the cover portion 15 and a radial extension 17 that extends radially inwardly from the cover portion 15. Each part of the core metal 11 is included in the fixed portion 13, the cover portion 15 and the axial extension 16. The axial extension 16 extends axially inwardly beyond an axially outer surface of the retainer such that it overlaps the retainer, and has a taper end portion 18. The taper end portion 18 has an opposite surface 20 that is opposite to an outer peripheral surface 2A of the inner ring 2 and forms a narrow passage 19 between the opposite surface 20 and the outer peripheral surface 2A of the inner ring 2, and a rake face 21 which forms a specified rake angle (about 45°) with the opposite surface 20. The core metal 11 has a part 11A that extends axially inwardly from the cover portion 15. In regard to the part 11A, its foremost end 11A-1 is positioned in the vicinity of the taper end portion 18. Further, the foremost end 11A-1 is placed axially inwardly with respect to an axial outermost end 2A-1 of the outer peripheral surface 2A of the inner ring 2. The radial extension 17 abuts on a side wall 22A located axially outwardly of a radially recessed annular groove 22 formed at an axial end portion adjacent to the outer peripheral surface 2A of the inner ring 2. The radial extension 17 has axially penetrating notches 23. The notches 23 are formed in a plurality of portions of the radial extension 17 circumferentially at specified intervals. According to the bearing sealing device having the above construction, the opposite surface 20 of the taper end portion 18 forms a narrow passage 19 between the opposite surface 20 and the outer peripheral surface 2A of the inner ring 2. The narrow passage 19 allows air to pass easily, but it allows grease to hardly pass therethrough. That is to say, the narrow passage 19 does not substantially allow grease to pass therethrough. Therefore, grease moving axially outwardly on the outer peripheral surface 2A of the inner ring 2 is moved along the rake face 21 having a specified rake angle (about 45°) upon reaching the taper end portion 18. The rake angle of the rake face 21 may be smaller than 45°. The grease is, so to speak, scooped up by the rake face 21. Then, the grease moving along the rake face 21 is guided along the cover portion 15 to the outer ring 1. Furthermore, according to the first embodiment, the axial extension 16 includes the part 11A of the core metal 11 where the foremost end 11A-1 is in the vicinity of the taper end portion 18. Further, the foremost end 11A-1 of the part 11A is located axially inwardly with respect to the axial outermost end 2A-1 of the outer peripheral surface 2A of the inner ring 2. Therefore, the axial extension 16 is prevented from being bent radially outwardly by a centrifugal force generated when the outer ring 1 is rotated. Therefore, even when a centrifugal force is generated on the axial extension 16 due to the rotation of the outer ring 1, the possible leak of grease is always prevented substantially completely. Furthermore, by virtue of the existence of the foremost end 11A-1, a clearance between the axial extension 16 and the outer peripheral surface 2A of the inner ring 2 is set with high accuracy. Furthermore, the part 11A of the core metal 11 exists continuously in an annular form around the entire outer peripheral surface of the inner ring 2. Therefore, the axial extension 16 is prevented from being bent radially outwardly by the centrifugal force throughout the entire periphery. Therefore, even when a centrifugal force is generated on the axial extension 16 due to the rotation of the outer ring 1, the possible leak of grease is always prevented substantially completely. The retainer 5W supports the balls 3 arranged between the outer ring 1 and the inner ring 2 axially inwardly with respect to the axial extension 16. The retainer 5W has a slant surface 5W-a arranged oppositely and approximately in parallel to the rake face 21 of the taper end portion 18. A distance L1 between the slant surface 5W-a and the rake face 21 is set greater than a distance L2 (L1 > L2) between the retainer 5W and the outer peripheral surface 2A of the inner ring 2. It was found through an experiment that, when the balls 3 are rotating while rolling between the outer ring 1 and the inner ring 2, the lubricating oil circulates in a route of (balls 3) → (a space between the outer peripheral surface 2A of the inner ring 2 and the retainer 5W) → (a space between the rake face 21 of the taper end portion 18 of the axial extension 16 and the retainer 5W) → (a space between the cover portion 15 and the retainer 5W) → (a space between the retainer 5W and the outer ring 1) → (balls 3) as indicated by void arrows in Fig. 1. Therefore, the dimensional setting of L1 > L2 means that the lubricating oil path through the space between the rake face 21 of the taper end portion 18 of the axial extension 16 and the retainer 5W is made wider than the lubricating oil path through the space between the outer peripheral surface 2A of the inner ring 2 and the retainer 5W. With this arrangement, the lubricating oil from the space between the outer peripheral surface 2A of the inner ring 2 and the retainer 5W is guided to the space between the rake face 21 of the taper end portion 18 of the axial extension 16 and the retainer 5W, and the lubricating oil is hardly introduced into the narrow passage 19 between the inner ring 2 and the taper end portion 18. Therefore, the first embodiment has the effect of preventing the lubricating oil from intruding into the space between the inner ring 2 and the taper end portion 18. Therefore, in cooperation with the sealing effect produced by the taper end portion 18, the possible leak of the lubricating oil is more surely prevented. In the first embodiment, the axial foremost end of the taper end portion 18 has an acutely sharpened configuration. However, as shown in Fig. 1B, it is acceptable to provide a recess portion 25 that is recessed radially outwardly from the opposite surface 20 that forms the narrow passage 19 and recessed axially outwardly from the foremost end of the rake face 21 at the axial foremost end of the taper end portion 18. With this arrangement, the grease that has axially moved along the outer peripheral surface 2A of the inner ring 2 and reached the taper end portion 18 is firstly caught in the recess portion 25 at the axially innermost end. Then, a mass F of the grease is retained in the recess portion 25. Therefore, an oil component of the grease is intercepted in the mass F of the grease, so that the oil component of the grease is prevented from entering the narrow passage 19. Furthermore, as shown in Fig. 1C, it is acceptable to provide a small projection 26 that is put in contact with the outer peripheral surface 2A of the inner ring 2 on the opposite surface 20 of the taper end portion 18. The small projection 26 can slightly bend to thereby allow air to pass therearound. With this arrangement, the small projection 26 intercepts a very small amount of the oil component of the grease, and therefore the very small amount of the oil component of the grease is prevented from leaking through the narrow passage 19. Second Embodiment Next, Fig. 2 shows a part of a second embodiment. The second embodiment includes an axial extension 46 that extends axially inwardly from the cover portion 45. The axial extension 46 has a taper end portion 48. The taper end portion 48 includes an opposite surface 50 that is opposed to the outer peripheral surface 32A of the inner ring 32 and forms a narrow passage 49 between the opposite surface 50 and an outer peripheral surface 32A of the inner ring 32, and a rake face 51 that forms a specified rake angle (approximately 45°) with the opposite surface 50. The axial extension 46 has two recess portions 52 and 53 located axially outwardly with respect to the taper end portion 48. The recess portions 52 and 53 are recessed radially outwardly by a specified dimension with respect to the opposite surface 50 of the taper end portion 48. The axial extension 46 has an annular projection 55 that extends circumferentially between the recess portions 52 and 53, and an annular projection 56 that adjoins axially outwardly to the recess portion 53. The annular projections 55 and 56 have opposite surfaces 55A and 56A opposite to the outer peripheral surface 32A of the inner ring 32. The opposite surfaces 55A and 56A are arranged in approximately the same radial positions as that of the opposite surface 50 of the taper end portion 48. Therefore, the opposite surface 55A and 56A form narrow passages 57 and 58 between them and the outer peripheral surface 32A of the inner ring 32. The core metal 41 has a part 41A that extends axially inwardly from the cover portion 45. The part 41A extends axially along the outer peripheral surface 32A of the inner ring 32 oppositely to the outer peripheral surface 32A, and its foremost end 41A-1 is positioned in the vicinity of the taper end portion 48. There are provided two recess portions 52 and 53 located axially outwardly with respect to the taper end portion 48. However, there may be provided three or more such recess portions. According to the bearing sealing device having the above construction, the opposite surface 50 of the taper end portion 48 forms the narrow passage 49 between the opposite surface 50 and the outer peripheral surface 32A of the inner ring 32. The narrow passage 49 allows air to pass easily, but it allows grease to hardly pass therethrough. Therefore, as indicated by an arrow A in Fig. 2, the grease moving axially outwardly on the outer peripheral surface 32A of the inner ring 32 is moved along the rake face 51 having a specified rake angle (about 45°) upon reaching the taper end portion 48. The grease is, so to speak, scooped by the rake face 51. Then the grease moving along the rake face 51 is guided along the cover portion 45 to the outer ring 31. Furthermore, the grease that has accidentally passed around the taper end portion 48 is intercepted in the recess portion 52, and the grease that has passed through the narrow passage 57 is intercepted in the subsequent recess portion 53. Therefore, according to the second embodiment, the possible leak of grease is more surely prevented. Furthermore, according to the second embodiment, the axial extension 46 includes the part 41A of the core metal 41 that is arranged oppositely to the outer peripheral surface 32A of the inner ring 32, where the foremost end 41A-1 of the part 41A extends to an axial position in the vicinity of the taper end portion 48. Therefore, the part 41A can prevent the axial extension 46, from being bent radially outwardly by a centrifugal force generated when the outer ring 31 is rotated. Therefore, even when a centrifugal force is generated on the axial extension 46 due to the rotation of the outer ring 31, the possible leak of grease is always prevented substantially completely. Furthermore, by virtue of the existence of the part 41A, a clearance between the axial extension 46 and the outer peripheral surface 32A of the inner ring 32 is set with high accuracy. Furthermore, the part 41A of the core metal 41 exists continuously in an annular form around the entire outer peripheral surface of the inner ring 32. Therefore, the axial extension 46 is prevented from being bent radially outwardly throughout the entire periphery by the centrifugal force. Therefore, even when a centrifugal force is generated due to the rotation of the outer ring 31, the possible leak of grease is always prevented substantially completely. Third Embodiment Next, Fig. 3 shows a third embodiment. The third embodiment differs from the first embodiment in the construction of a retainer 61 of the bearing. Therefore, the third embodiment will be described intensively on the retainer 61. It should be noted that the same elements as in the first embodiment are shown by the same reference numerals as in the first embodiment. The retainer 61 has a projection 63 that projects radially inwardly from an inner radial portion 62. The projection 63 has an opposite surface 63A arranged oppositely to the outer peripheral surface 2A of the inner ring 2 axially inwardly with respect to the taper end portion 18, and the opposite surface 63A forms a narrow passage 65 between the opposite surface 63A and the outer peripheral surface 2A of the inner ring 2. The narrow passage 65 allows air to pass easily, but it allows grease to hardly pass therethrough. Therefore, according to the third embodiment, as indicated by arrows C in Fig. 3, the grease moving axially outwardly is intercepted by the projection 63 before the taper end portion 18. Therefore, according to the third embodiment, the possible leak of grease is more surely prevented. The retainer of the bearing is implemented by a crown-shaped retainer made of resin in the first through third embodiments, however, it may be a wave-shaped retainer made of iron. Furthermore, the sealing device is provided axially on one side of the bearing in the first through third embodiments, however, it may be provided on both sides of the bearing. The above embodiments employ balls as rolling members. But, rollers may also be used as rolling members. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims: A bearing comprising: a bearing sealing device provided between an outer ring (1) and an inner ring (2) of the bearing in which the outer ring (1) rotates, said device sealing a space between the outer ring (1) and the inner ring (2) and being securely fixed to the outer ring (1) so as to rotate together with the outer ring (1), the sealing device including a portion (13) fixed to the outer ring (1), a cover portion (15) which extends radially inwardly of the outer ring (1,31) from the fixed portion (13) and covers the space between the outer ring (1) and the inner ring (2), and an axial extension (16) which is made of an elastic material and extends in an axially inward direction from the cover portion (15), wherein the axial extension (16) includes a taper end portion (18) having a surface (20) which is opposed to an outer peripheral surface (2A) of the inner ring (2) and forms between said opposing surface (20) and the outer peripheral surface (2A) a narrow passage (19) having a width such that air is allowed to pass comparatively easily and oil is allowed to pass only with comparative difficulty, and a rake face (21) at an oblique angle to said opposing surfaces (20), a core metal extending through the fixed portion (13) and the cover portion (15) respectively; and a retainer (5W) which holds rolling members (3) of the bearing being arranged between the outer ring (1) and the inner ring (2) axially inwardly with respect to the axial extension (16), characterised in that: the axial extension (16) extends axially inwardly beyond an axially outer surface of the retainer such that the axial extension overlaps the retainer (5W); the core metal (11) projects axially inwardly from the cover portion (15) through the axial extension (16) up to a position on a radially outer side of the outer peripheral surface (2A) of the inner ring (2), where a foremost end of the core metal (11) is located in the vicinity of the taper end portion (18); and the retainer (5W) has a slant surface (5W-a) radially outwardly of an inner circumferential surface of the retainer such that the distance (L1) between the retainer (5W) and the rake face (21) of the taper end portion (18) of the axial extension (16) is set larger than the distance (L2) between the retainer (5W) and the outer peripheral surface (2A) of the inner ring (2). A bearing as claimed in claim 1, wherein the taper end portion (18) of the sealing device comprises at its axial innermost end a recess portion (25) which is recessed radially outwardly from the opposing surface (20) that forms the narrow passage (19) and is recessed axially outwardly from a foremost end of the rake face (21). A bearing as claimed in claim 1, wherein the axial extension (46) of the sealing device comprises a recess portion (52,53) which is located axially outwardly with respect to the taper end portion (48) and is recessed radially outwardly with respect to the opposite surface (50) of the taper end portion (48). A bearing as claimed in any one of claims 1 to 3, wherein that part (11A) of the core metal (11) in the axial extension (16) has an annular configuration extending continuously around an entire outer periphery of the inner ring (2). A bearing according to any one of the preceding claims wherein the retainer (61) has a projection (63) on its radially inner face and said minimum distance between the retainer and the outer peripheral surface (2A) of the inner ring (2) is defined between the projection and said surface. A bearing according to any one of the preceding claims wherein the retainer (61) is crown-shaped and made of resin, a projection (63) on the retainer including a surface (63A) opposed to the outer peripheral surface (2A) of the inner ring (2) axially inwardly with respect to the taper end portion (18), said surfaces forming a further narrow passage (65) having a width such that air is allowed to pass comparatively easily and oil is allowed to pass only with comparative difficulty.

Inventors: KAJIHARA KAZUHISA, TANIYAMA MASATOSI, UENO HIROSHI, YANAI KUNIO, KAJIHARA, KAZUHISA, TANIYAMA, MASATOSI, UENO, HIROSHI, YANAI, KUNIO, Kajihara, Kazuhisa, c/o Koyo Seiko Co., Ltd., Taniyama, Masatosi, c/o Koyo Seiko Co., Ltd., UENO, HIROSHI, C/O KOYO SEIKO CO., LTD., Yanai, Kunio, c/o Koyo Seiko Co., Ltd.
Applicants: KOYO SEIKO CO, KOYO SEIKO CO., LTD.
Application year: 1996
Main classification: F16C33
IPC codes: F16C33