Patent Publication Number: US-2023137648-A1

Title: Sealed rolling bearing

Description:
TECHNICAL FIELD 
     The present invention relates to a sealed rolling bearing used, e.g., as a deep groove ball bearing for an automotive engine accessory pulley. 
     BACKGROUND ART 
     In the markets of, e.g., emerging countries where road conditions and climates are severe for automobiles, automobiles are used in extremely severe environments, for example, in environments where automobiles have to travel while being partially submerged in water, or their engine compartments are washed at high pressure. 
     Therefore, high sealing performance is required for bearings for engine accessory pulleys, as mentioned above. As bearings that meet this requirement, sealed rolling bearings are disclosed in, e.g., the below-identified Patent Documents 1 and 2. 
     The sealed rolling bearing (sealing device for a rolling bearing) of Patent Document 1 is a bearing of which the outer ring is rotatable. This bearing includes, between the inner and outer rings, seal members sealing the rolling element installation space. Outside the respective seal members, slingers sized to lie within the width range of the bearing, are supported by the inner ring. The slingers prevent external splashed muddy water from entering the bearing, 
     Each seal member includes, on the outer side surface thereof, a side lip inclined in a direction in which the distance between the side lip and the outer ring narrows toward the distal end (protruding end) of the side lip, so as to define a labyrinth portion that hinders the inflow of, e.g., muddy water, between the distal end of the seal lip and the inner side surface of the slinger, thereby improving sealing performance. 
     The sealed rolling bearing (sealing device for a rolling bearing) of Patent Document 2 includes, as with the bearing of Patent Document 1, both seal members and slingers. However, this bearing is different from the bearing of Patent Document 1 in that two seal members are disposed on each side, instead of providing a labyrinth portion. 
     PRIOR ART DOCUMENT(S) 
     Patent Document(s) 
     
         
         Patent document 1: Japanese Unexamined Patent Application Publication No. 2013-145018 
         Patent document 2: Japanese Unexamined Utility Model Application Publication No. H04-50724 
       
    
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     In the bearing of Patent Document 1, the radially outer end (edge) of each slinger is opposed to the radially inner surface of the outer ring. However, with this arrangement, since the gap between the radially outer edge of each slinger and the outer ring (this gap acts as an entry path for entry of, e.g., muddy water) has only a length (path length), in the direction of the center axis of the bearing, corresponding to the material thickness of the slinger, there is a limit to improving sealing performance. 
     In order to overcome this problem, in the bearing of Patent Document 1, a side lip is disposed on each seal lip such that a labyrinth portion is defined between the side lip and the slinger, thereby increasing the number of entry hindering portions through which, e.g., muddy water does not pass easily. 
     However, since only a single labyrinth portion is defined between the side lip of each seal member and the slinger, e.g., muddy water that has flowed into the bearing through the gap between the slinger and the outer ring could enter the portion inside the slinger through the labyrinth portion, and stay in the space between the slinger and the seal member, and then could infiltrate into the installation space of the rolling elements through the sealed portion sealed by the seal member. Thus, this arrangement does not provide reliable sealing. 
     Since the bearing of Patent Document 2 uses two seal members on each side of the bearing, it is considered that this bearing provides better sealing performance than the bearing of Patent Document 1. However, since two seal members are used, the number of bearing components increases, and the bearing width also increases inevitably. Thus, it is impossible to meet the requirements of reducing a rise in the bearing cost and reducing the size of the bearing. 
     For the bearing of Patent Document 1, since the side lip on the outer side surface of each seal member is inclined in a direction in which the distance between the side lip and the outer ring narrows toward the distal end of the side lip, demolding is difficult after forming the seal member in a mold using rubber. Also, the moldability of the seal member is not good. 
     It is an object of the present invention to provide a sealed rolling bearing (i) which includes, between each slinger and the outer ring, entry hindering portions that make the inflow of, e.g., muddy water more difficult than in conventional bearings; (ii) in which the number of bearing components does not increase; and (iii) of which the bearing width does not increase. 
     Means for Solving the Problems 
     In order to achieve the above object, the present invention provides a sealed rolling bearing comprising: two seal members (seals or shields) disposed between an inner ring and an outer ring, each on either side of a rolling element installation area of the bearing, so as to seal the rolling element installation area, and two slingers each disposed outside of a respective one of the two seal members, and sized to lie within a width range of the bearing, the slingers being supported by the inner ring, and preventing, e.g., external splashed muddy water from entering the bearing, wherein the sealed rolling bearing is improved in that each of the slingers includes: a radially inner bent portion formed by inwardly bending a radially inner side of the slinger, and press-fitted to an outer periphery of the inner ring; and a radially outer bent portion formed by inwardly bending a radially outer side of the slinger such that a labyrinth portion is defined between the radially outer bent portion and a radially inner surface of the outer ring, the labyrinth portion having a path length, in an axial direction of the bearing, longer than a material thickness of the slinger. 
     Preferred modes of the above sealed rolling are enumerated below. 
     Mode (1): The seal members are rubber seals each reinforced by a metal core, and including at least one side lip disposed on an outer side surface of the rubber seal, and protruding in the axial direction of the bearing, the at least one side lip having a distal end located inwardly of the radially outer bent portion of the slinger such that a labyrinth portion is defined between the at least one side lip and an inner side surface of a body of the slinger. 
     Mode (2): The at least one side lip of each of the seal members includes demolding tapers, the demolding tapers being such that a radially outer surface and a radially inner surface of the at least one side lip are inclined in opposite directions to each other, relative to respective reference lines parallel to a center axis of the bearing. 
     Mode (3): The at least one side lip of each of the seal members comprises a plurality of side lips radially displaced from each other. 
     Mode (4): The slingers are formed by pressing. 
     Mode (5): The slingers are formed of a cold-rolled material. 
     Effects of the Invention 
     In the sealed rolling bearing of the present invention, since, by inwardly bending the radially outer portion of each slinger, a labyrinth portion whose path length in the axial direction of the bearing is longer than the material thickness of the slinger is defined between the radially outer bent portion and the radially inner surface of the outer ring, the flow resistance of e.g., muddy water at the labyrinth portion is larger than in the above-described bearing of Patent Document 1. 
     Also, by making the distal end of the radially outer bent portion of each slinger located close to a respective one of annular protrusion formed on the radially inner surface of the outer ring (protrusion for defining a seal fitting groove), it is possible to define a labyrinth portion having a path area smaller than that of the labyrinth portion between the radially outer bent portion of the slinger and the radially inner surface of the outer ring. These improve sealing performance. 
     Only a single seal member is required on each side of the bearing, and thus the number of bearing components does not increase. By mounting only a single seal member to each side of the bearing, it is possible to reduce the width of the bearing, and thus to reduce the size of the bearing compared to the bearing of Patent Document 2. 
     In the sealed rolling bearing of the above mode (1), the at least one side lip on each rubber seal is located inwardly of the radially outer bent portion of the slinger such that a meandering entry path for entry of, e.g., muddy water from outside is defined. The meandering shape further increases the path length of the entry path, and also complicates the flow of, e.g., muddy water entering the entry path, thus further increasing sealing performance. 
     For the above mode (3), in which a plurality of side lips are disposed on each seal member, it is possible to increase the number of entry (e.g., muddy water-entry) hindering portions, and thus to further increase sealing performance. 
     Also, for the above mode (2), in which the at least one side lip of each seal member includes demolding tapers, it is possible to smoothly separate the mold, and thus to easily form the seal member by injection molding. 
     Also, by using the slingers of the above mode (4) or (5), it is possible to increase the productivity of slingers, and thus to avoid a rise in the manufacturing cost. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a sectional view of a portion of a sealed rolling bearing according to the present invention. 
         FIG.  2    is an enlarged sectional view illustrating the positional relationship between side lips on each seal member and a slinger in the sealed rolling bearing of  FIG.  1   . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     A sealed rolling bearing embodying the present invention is described below with reference to  FIGS.  1  and  2   . 
     As illustrated in  FIG.  1   , the sealed rolling bearing  1  shown is a deep groove ball bearing of which both sides are sealed, and which is constituted by the combination of an inner ring  2 ; an outer ring  3 ; rolling elements  4  disposed between the inner and outer rings; a cage  5  retaining the rolling elements  4 ; two seal members  6 ; and two slingers  7 . 
     The two seal members  6  are disposed each on either side of a rolling element installation area  8  between the inner ring  2  and the outer ring  3 . The seal members  6  shown are rubber seals each including a metal core  6  for reinforcement, and mounted to the outer ring  3 , which is rotatable. Circumferentially continuously extending side lips  6   b  protrude from the outer side surface of the rubber seal, in the axial direction of the bearing. 
     While the seal members  6  shown each has a plurality of side lips  6   b  radially displaced from each other, the number of the side lips  6   b  on the seal member is not particularly limited. 
     The slingers  7  are disposed outside of the respective seal members  6 . The slingers  7  shown are formed by pressing a cold-rolled material, and each includes a body  7   a  having a flat plate shape. The radially inner and outer sides of the slinger  7  are inwardly bent, respectively, from the inner and outer edges of the body  7   a , to extend toward the rolling element installation area  8 , thus forming a radially inner bent portion  7   b  and a radially outer bent portion  7   c , respectively. 
     The radially inner bent portion  7   b  and the radially outer bent portion  7   c  are straight portions having a circular annular shape, and extending parallel to the center axis of the bearing. Each slinger  7  is retained by the inner ring  2 , which is fixed, with the radially inner bent portion  7   b  press-fitted to the outer periphery of the inner ring  2 . 
     On the other hand, the radially outer bent portion  7   c  is located as close as possible to the radially inner surface of the outer ring  3 , so as to define a labyrinth portion  9  whose path length in the axial direction of the bearing is longer than the material thickness t of the slinger  7  (see  FIG.  2   ), between the radially inner surface of the outer ring  3  and the radially outer surface of the radially outer bent portion  7   c.    
     Further, the distal end of the radially outer bent portion  7   c  is located as close as possible to a respective one of two annular protrusions  3   a  formed on the radially inner surface of the outer ring  3 , so as to define a labyrinth portion  10  having a path area smaller than that of the labyrinth portion  9 , between the annular protrusion  3   a  and the distal end of the radially outer bent portion  7   c.    
     The annular protrusions  3   a  are formed for the purpose of defining, in the radially inner periphery of the outer ring  3 , seal fitting grooves  3   b  for supporting the proximal ends of the respective seal members  6 . 
     The side lips  6   b  of each seal member  6  each have its distal edge portion which has dimension B (see  FIG.  2   ) located inwardly of the radially outer bent portion  7   c  of the slinger  7 , thereby defining labyrinth portions  11  between the body  7   a  of the slinger  7  and the distal edges of the respective side lips  6   b , too. 
     By making the distal edge portions of the side lips  6   b  located inwardly of the radially outer bent portion  7   c  of the slinger  7 , the seal lips  6   b  and the radially outer bent portion  7   c  overlap with each other by dimension B. This causes meandering of the path through which e.g., muddy water could enter from outside (i.e. the path extending from the labyrinth portion  10  to the portion of a main lip  6   c  of each seal member  6  in sliding contact with the inner ring  2 ). The meandering shape increases the path length of the entry path, and also complicates the flow of, e.g., muddy water entering the entry path. 
     Also, the labyrinth portions  11  between the body  7   a  of each slinger  7  and the respective side lips  6   a  add to the number of entry hindering portions, thus further improving sealing performance. 
     The path widths C of the labyrinth portions  11  in  FIG.  2    are set to C=(A−B), where A is the dimension of the radially outer bent portion  7   c  of the slinger  7  in the axial direction of the bearing. The path width C of the labyrinth portion  11  are exaggeratedly shown. In order to reduce a rise in the rotation torque caused by the contact of the side lips  6   b  of each seal member  6  with the body  7   a  of the slinger, the path widths C are set to C  20  in view of gaps inside of the bearing, and assembling errors, thereby preventing the side lips  6   b  from coming into contact with the body  7   a.    
     Each side lip  6   b  of each seal member  6  is preferably provided with demolding tapers a and  8  as illustrated in  FIG.  2   . The demolding tapers a and  8  are, respectively, the inclination angle of the radially outer surface of the side lip  6   b  relative to a reference line L 1  parallel to the center axis of the bearing, and the inclination angle of the radially inner surface of the side lip  6   b  relative to a reference line L 2  parallel to the center axis of the bearing. The demolding tapers a and B are such that the radially outer and inner surfaces of the side lip  6   b  are inclined in opposite directions to each other. 
     In order to reduce the speed at which, e.g., muddy water flowing down onto the radially outer surface of the side lip flows down on this surface, the inclination angle (taper α) of the radially outer surface is preferably smaller than the inclination angle (taper β) of the radially inner surface. The taper α is preferably 5 degrees or less. 
     The taper β is preferably set to 15 degrees or more and 20 degrees or less. By setting the taper β within this range, e.g., muddy water flowing on the radially outers surface of the side lip  6   b  and reaching the distal end thereof flows the root side of the side lip  6   b  along the radially inner surface thereof, thus reducing the amount of muddy water dripping down directly from the distal end of the side lip  6   b . In addition, by setting the taper β at such a large value, muddy water that has once entered the space between the seal member  6  and the slinger  7  can be discharged easily by a centrifugal force. 
     By providing the demolding tapers, the seal members  6 , which are rubber seals, can be smoothly removed from the mold after being formed by injection molding, and thus can be easily manufactured. 
     As in the shown example, a plurality of side lips  6   b  are preferably disposed on each seal member  6 , or a rubber seal, so as to be radially displaced from each other. 
     The larger the number of the side lips  6 , the larger the number of the entry hindering portions, thus improving sealing performance more effectively. 
     While the seal members  6  shown are rubber seals, shields made of hard resin or metal which are used in shielded bearings may be used instead, as the seal members  6 . 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1 : Sealed rolling bearing 
           2 : Inner ring 
           3 : Outer ring 
           3   a : Annular protrusion 
           3   b : Seal fitting groove 
           4 : Rolling element 
           5 : Cage 
           6 : Seal member 
           6   a : Metal core 
           6   b : Side lip 
           6   c : Main lip 
           7 : Slinger 
           7   a : Body 
           7   b : Radially inner bent portion 
           7   c : Radially outer bent portion 
           8 : Rolling element installation area 
           9 ,  10 ,  11 : Labyrinth portion 
         A: Dimension, in the axial direction of the bearing, of the radially outer bent portion of the slinger 
         B: Dimension of the distal end portion of the side lip that is located inwardly of the radially outer bent portion of the slinger 
         C: Path width of the labyrinth portion between the distal end of the side lip and the body of the slinger 
         t: Material thickness t of the slinger 
         α, β: Demolding taper 
         L 1 , L 2 : Reference line of the demolding taper