Patent Publication Number: US-2020292082-A1

Title: Sealing device

Description:
FIELD 
     The present invention relates to a sealing device which can be used in car hub bearings, and the like. 
     BACKGROUND 
     A hub seal as a sealing device used in car hub bearings is known (for example, Japanese Patent Laid-Open Publication No. 2017-40295, hereinafter referred to as “Patent Literature 1”). The sealing device disclosed in Patent Literature 1 is arranged between an outer ring  2  and an inner ring  5  which rotate relative to each other about a common axis, and seals against leakage between an atmosphere side and a structurally interior side in which balls  6  of a bearing are accommodated. 
     The sealing device in Patent Literature 1 includes a metal core  11  which is fitted and fixed onto an inner peripheral surface  2   a  of the outer ring, and an elastic member  12  which is formed of rubber and is fastened to the metal core by vulcanization molding (see paragraphs [0012], [0014], and [0016] in Patent Literature 1). 
     The elastic member includes three lips which has their end in tight contact with the inner ring. One of the three lips is a radial lip  122  which has an end extending toward the structurally interior side, and the other two are axial lips  121  which have an end extending toward the atmosphere side (see paragraph [0016] and  FIG. 2  in Patent Literature 1). 
     BRIEF SUMMARY 
     Technical Problem 
     Such hub seals are required to contribute low friction torque and improve muddy water resistance. For example, because the hub seal in Patent Literature 1 has the two axial lips ( 121 ), which have an end extending toward the atmosphere side, this hub seal will improve muddy water resistance. 
     However, the greater the number of the lips, the higher the sliding resistance between the lips and their contact surface. As a result, it is difficult for a hub seal which has a number of lips to contribute low friction torque. 
     Therefore, it is an object of the present invention is to prevent increase of contact pressure of lips on their contact surface. 
     Solution to Problem 
     Torque is increased by increase of the number of the lips. In this case, the torque is increased not only by the number of the lips but also by increase of contact pressure of lips on their contact surface. Such increase of contact pressure of a lip includes an increase caused by negative pressure which is produced in a space between two lips by machining marks on their contact surface. 
     For example, in the case of the hub seal in Patent Literature 1, closed spaces are defined between the two axial lips ( 121 ), and between the radial lip ( 122 ) and one of the axial lips ( 121 ) which is adjacent to this radial lip. Accordingly, in a certain direction of machining marks of their contact surface of the inner ring, air will leak from the spaces so that negative pressure is produced. As a result, the contact pressure of the lips on their contact surface increases. 
     A sealing device according to the present invention is configured to be interposed between an exterior-side member and an interior-side member which rotate about a common axis relative to each other, the sealing device including: 
     a metal ring fitted into and fastened to an inner periphery of the exterior-side member; and 
     a lip portion formed of a rubber-like elastic material and fastened to the metal ring by vulcanization, the lip portion including
         an annular grease lip extending toward a structurally interior side, the grease lip having a first end,   an annular side lip extending toward an atmosphere side, the side lip having a second end, and   an annular intermediate lip arranged between the grease lip and the side lip, the annular intermediate lip extending toward the interior-side member, the intermediate lip having a third end,       

     the first end, the second end and the third end configured to contact the interior-side member, 
     wherein the side lip has a spiral protruding/recessed part formed on a surface facing the intermediate lip, the protruding/recessed part running in a direction opposite to a direction of machining marks of the interior-side member. 
     Advantageous Effects 
     According to the present invention, increase of contact pressure of lips on their contact surface can be prevented. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical cross-sectional view of a hub seal according to an embodiment. 
         FIG. 2  is a cross-sectional perspective view of the hub seal according to the embodiment. 
         FIG. 3  is an enlarged perspective view of a surface of a side lip to be in tight contact with an inner ring. 
     
    
    
     DETAILED DESCRIPTION 
     The following description will describe a sealing device according to an embodiment with reference to drawings. The sealing device according to this embodiment is a hub seal which is used in car hub bearings (not shown entirely). 
     As shown by single-dot-dashed lines in  FIG. 1 , a hub bearing  51  includes an outer ring (exterior-side member)  52  and an inner ring (interior-side member)  53 . 
     The inner ring  53  has a vertical surface  53   a , a horizontal surface  53   b , and a curved surface  53   c . The vertical surface  53   a  and a horizontal surface  53   b  extend roughly perpendicularly to each other. The curved surface  53   c  is interposed between the vertical surface  53   a  and the horizontal surface  53   b . The horizontal surface  53   b  communicates with an atmosphere side A. The vertical surface  53   a  communicates with a structurally interior side B. The outer ring  52  has an inner peripheral surface  52   a  which faces the horizontal surface  53   b  of the inner ring  53 . A bearing (not shown) is interposed between the outer ring  52  and a part of the inner ring  53  which extends from the vertical surface  53   a  toward the structurally interior side B. More specifically, the bearing is accommodated in the structurally interior side B and is applied with grease (not shown). 
     A hub seal  101  according to this embodiment includes a metal ring  111  and a lip portion  131  which is fastened to the metal ring  111 . 
     The metal ring  111  includes a horizontal part (first horizontal part)  111   a , a bent part (a first bent part)  111   b , a bent part (second bent part)  111   c , and a horizontal part (second horizontal part)  111   d . The horizontal part  111   a  extends in a horizontal direction and has one end of the metal ring on the atmosphere side A. The bent part  111   b  is has a bent central section having a sectionally U shape which bulges toward the outer peripheral side. The bent part  111   c  is has a bent shape as a sectionally U shape which bulges toward the inner peripheral side. The horizontal part  111   d  extends in a horizontal direction and has another end of the metal ring on the structurally interior side B which is opposite to the atmosphere side A. The horizontal part  111   a  is fitted into the inner peripheral surface  52   a  of the outer ring  52 . The bent part  111   b  abuts on a structurally interior-side surface  52   b  of the outer ring  52  which is located on the structurally interior side B. Accordingly, the metal ring  111  is positioned on and fastened to the outer ring  52 . 
     The lip portion  131  is a rubber-like elastic body and is fastened to the metal ring  111  by vulcanization as shown in  FIGS. 1 and 2 . The lip portion  131  includes a grease lip  132 , a side lip  133 , an intermediate lip  134 , and a labyrinth lip  135 . 
     The grease lip  132  has an annular shape. The grease lip  132  extends toward the structurally interior side B, and has an end (first end)  132   a . The grease lip  132  extends from the end of the horizontal part llld of the metal ring  111  toward the vertical surface  53   a  of the inner ring  53 . The end  132   a  of the grease lip  132  is brought in tight contact with the vertical surface  53   a.    
     The side lip  133  has an annular shape. The side lip  133  extends toward the atmosphere side A, and has an end (second end)  133   a . The side lip  133  extends from a connection part between the bent part  111   c  and the horizontal part  111   d  of the metal ring  111  toward the horizontal surface  53   b  of the inner ring  53 . The end  133   a  of the side lip  133  is brought in tight contact with the horizontal surface  53   b.    
     The intermediate lip  134  is arranged between the grease lip  132  and the side lip  133 . The intermediate lip  134  extends from a part in proximity to a base of the grease lip  132  toward the curved surface  53   c  of the inner ring  53 . The intermediate lip  134  has an end (third end)  134 a which is brought in tight contact with the curved surface  53   c.    
     The labyrinth lip  135  has an annular shape. The labyrinth lip  135  is arranged on the atmosphere side A with respect to the grease lip  132 , the side lip  133  and the intermediate lip  134 . The labyrinth lip  135  extends toward the atmosphere side A, and has an end  135   a . The labyrinth lip  135  extends from a part in proximity to the end of the horizontal part  111   a  of the metal ring  111  toward the horizontal surface  53   b  of the inner ring  53 . The labyrinth lip  135  does not contact the horizontal surface  53   b  so that a very small gap G is created between the labyrinth lip  135  and the horizontal surface  53   b.    
     As discussed above, the ends  132   a ,  133   a , and  134   a  of the grease lip  132 , the side lip  133 , and the intermediate lip  134  are brought in tight contact with the inner ring  53 . According to this arrangement, a space S 1  is defined between the grease lip  132  and the intermediate lip  134 , and a space S 2  is defined between the side lip  133  and the intermediate lip  134 . 
     A spiral protruding/recessed part  151  is formed on a surface of the side lip  133  on the space S 2  side as shown in  FIG. 3 . The spiral protruding/recessed part  151  is formed by a continuously running protrusion  151   a . The space S 2  communicate with the atmosphere side A through segments of a groove  151   b  which are formed between turns of a line of the protrusion  151   a  adjacent to each other. 
     Contact surfaces (the vertical surface  53   a , the horizontal surface  53   b  and the curved surface  53   c ) of the inner ring  53  which the ends  132   a ,  133   a  and  134   a  of the lips  132 , 133  and  134  tightly contact are often formed rough when machined. Such surface roughness depends on machining accuracy. The surfaces can be smoother if they are machined more accurately. However, we necessarily accept a certain degree of roughness from viewpoint of manufacturability and the like. For this reason, asperities are produced by the machining on the contact surfaces of the inner ring  53  which the lips  132 , 133  and  134  tightly contact. As a result, very small gaps will be produced between the lips  132 , 133  and  134 , and their contact surfaces. 
     Such asperities which are produced on the contact surfaces will run in a particular direction, in other words, machining marks will appear. Air may be drawn out from the spaces S 1  and S 2  by sliding movement of the lips  132 , 133  and  134  with respect to their contact surfaces so that negative pressure is produced depending on conditions of the direction of machining marks. If negative pressure is produced in the spaces S 1  and S 2 , contact pressure of the lips  132 , 133  and  134  on their contact surfaces increases, and torque correspondingly increases. 
     The protruding/recessed part  151  of the side lip  133  according to this embodiment runs at a direction opposite to the direction of machining marks which remain on the contact surfaces of the inner ring  53  in tight contact with the lip  132 , 133  and  134 . According to this arrangement, negative pressure in the spaces S 1  and S 2  can be reduced. That is, the direction of the spiral groove  151   b  which is formed by the continuously running protrusion  151   a  is designed opposite to the direction of machining marks on its contact surface. 
     More specifically, the continuously running protrusion  151   a  preferably runs at an angle from 1° to 5° with respect to a perfect circle or at an angle within a range of +/−2° with respect to the machining marks which remain on its contact surface, and/or the protrusion  151   a  preferably has a turn pitch within a range from 0.04 to 0.4 mm 
     In the hub bearing  51  according to this embodiment, the inner ring  53  rotates with respect to the outer ring  52 . In the rotation, the hub seal  101  seals a gap between the outer ring  52  and the inner ring  53 . The grease lip  132  prevents leakage of grease from the structurally interior side B. The labyrinth lip  135 , the side lip  133 , and the intermediate lip  134  prevent the entry of muddy water and dust from the atmosphere side A. 
     The hub seal  101  is fastened to the outer ring  52 . In this arrangement, when the inner ring  53  rotates relative to the outer ring  52 , the lips  132 , 133  and  134  tightly contact the vertical surface  53   a , the horizontal surface  53   b  and the curved surface  53   c  as their corresponding contact surfaces of the inner ring  53 . During the rotation, air may be drawn out from the spaces S 1  and S 2  so that negative pressure is produced depending on conditions of the direction of machining marks which remain on the contact surface 
     The protruding/recessed part  151  is formed on one surface of the side lip  133  in this embodiment. The protruding/recessed part  151  extends at a direction opposite to the direction of machining marks which remain on its contact surfaces of the inner ring  53 . According to this arrangement, air on the atmosphere side A is drawn into the space S 1  by the sliding movement of the lips  132 , 133  and  134  on their contact surfaces of the inner ring  53 . Accordingly, the air drawn into the space S 1  compensates the air drawn out from the space S 1 . As a result, the space S 1  will not be brought into negative pressure. Consequently, increase of contact pressure of the lips  132 , 133  and  134  on their contact surfaces can be reduced. Therefore, increase of contact pressure of the lip portion  131  on their contact surface can be prevented. 
     The inventors of the present invention found that the negative pressure prevention effect in the space S 1  can be effectively provided under the aforementioned conditions, namely, 
     the protrusion  151   a  runs at an angle from  1 ° to  5 ° with respect to a perfect circle or
         at an angle range within  2 ° with respect to the machining marks which remain on the contact surface, and/or       

     the protrusion  151   a  has a turn pitch within a range from 0.04 to 0.4 mm 
     In this embodiment, because the protruding/recessed part  151  is formed by the continuously running protrusion  151   a , the turn pitch and width of the groove  151   b  which introduces air into the space S 2  can be easily and desirably designed by suitably designing the turn pitch and thickness of the protrusion  151   a . Also, the protruding/recessed part  151  can be easily formed by using a die (not shown) which forms the lip portion  131 . 
     Various changes and modifications can be made in practical applications. 
     The protruding/recessed part  151  according to this embodiment has been illustratively described to be formed by the spirally running protrusion  151   a  which is formed on one surface of the side lip  133 . That is, the groove  151   b  is formed between turns of a line of the protrusion  151   a  adjacent to each other by forming the protrusion  151   a . The protruding/recessed part is not limited to this embodiment. A protruding/recessed part  151  can be formed by forming a line of groove  151   b  on one surface of the side lip  133 . 
     Also, the protrusion  151   a  does not necessarily continuously run but can have discontinuous shapes as long as the discontinuous shapes form a spiral shape as a whole. That is, protrusions  151   a  can be discrete protrusion lines as long as the grooves  151   b  are formed between the protrusions  151   a  adjacent to each other, and air can be introduced into the space S 2  from the atmosphere side A through the grooves  151   b.    
     The protruding/recessed part  151  is only required to be formed in an area through which the atmosphere side A can communicate with the space S 2 . The protruding/recessed part can be entirely or partially formed on one surface of the side lip  133  as long as this requirement is satisfied. 
     Any changes and modifications can be made to other parts in the embodiment. 
     REFERENCE SIGNS LIST 
     
         
           51  . . . Hub Bearing 
           52  . . . Outer Ring 
           53  . . . Inner Ring 
           53   a  . . . Vertical Surface 
           53   b  . . . Horizontal Surface 
           53   c  . . . Curved Surface 
           101  . . . Hub Seal 
           111  . . . Metal Ring 
           111   a  . . . Horizontal Part 
           111   b  . . . Bent Part 
           111   c  . . . Bent Part 
           111 d . . . Horizontal Part 
           131  . . . Lip Portion 
           132  . . . Grease Lip 
           133  . . . Side Lip 
           134  . . . Intermediate Lip 
           135  . . . Labyrinth Lip 
           132   a ,  133   a ,  134   a ,  135   a . . . End 
           151  . . . Protruding/Recessed Part 
           151   a  . . . Protrusion 
         A . . . Atmosphere Side 
         B . . . Structurally Interior Side 
         G . . . Gap 
           51 , S 2  . . . Space