Patent Publication Number: US-2020278028-A1

Title: Sealing apparatus

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of International Patent Application No. PCT/JP2019/040688 filed on Oct. 16, 2019, which claims the benefit of Japanese Patent Application No. 2018-197018, filed on Oct. 18, 2018. The contents of these applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND 
     Technical Field 
     The present disclosure relates to a sealing apparatus to realize sealing between a shaft and a hole into which this shaft is to be inserted. 
     Related Art 
     In a vehicle, a general-purpose machine, or the like, in order to prevent leakage of an object to be sealed, such as, for example, a lubricant, and in order to seal a gap formed between a shaft and a hole into which this shaft is to be inserted, a sealing apparatus has been conventionally used. In such a sealing apparatus, sealing between the shaft and the sealing apparatus is realized by a seal lip being brought into contact with the shaft or an annular member attached to the shaft. Contact between this seal lip and the shaft for sealing also becomes sliding resistance (torque resistance) to the shaft. In recent years, in response to a request for fuel efficiency of a vehicle, or the like, there has been a demand for a sealing apparatus to reduce sliding resistance to the shaft, and to have a structure which can realize reduction of sliding resistance to the shaft while maintaining or improving sealing performance. 
     While it is considered to increase the number of seal lips to improve sealing performance of the sealing apparatus, sliding resistance increases as a result of the number of seal lips being increased. To address this, a sealing apparatus (end-face lip type oil seal) is disclosed where an end-face lip which tightly contacts a flange portion of a slinger in a slidable manner is provided instead of realizing sealing by increasing the number of seal lips (see, for example, Japanese Patent No. 5964167). 
     The sealing apparatus is also used as a member for providing sealing to a crank shaft of an automobile engine. There may be a case where a negative pressure is generated in a crank case of the automobile engine. 
     In a conventional sealing apparatus, there may be a case where, when a negative pressure is generated on the side of an object to be sealed, a distal end of an end-face lip is separated from a contact with a slinger at an outer side surface of a flange portion of the slinger so that a gap is formed between the distal end of the end-face lip and the outer side surface of the slinger. In this case, in the conventional sealing apparatus, there may be a case where a liquid, which is an object to be sealed, gets over the gap, and reaches an outer peripheral surface of a cylindrical portion. 
     The present disclosure has been made in view of the above-described problem, and it is an object of the present disclosure to provide a sealing apparatus having improved sealing performance when a negative pressure is generated on the side of the object to be sealed. 
     SUMMARY 
     To achieve the above-described object, the present disclosure is directed to a sealing apparatus for sealing a gap formed between a shaft and a hole into which the shaft is to be inserted, and having an annular shape, the sealing apparatus being characterized by including: a sealing apparatus body to be fitted into the hole; and a slinger to be attached to the shaft, wherein the sealing apparatus body includes a reinforcing ring and an elastic body portion, the reinforcing ring having an annular shape around an axis line, and the elastic body portion being formed of an elastic body which is attached to the reinforcing ring, and having an annular shape around the axis line, the slinger includes a flange portion which is a portion extending toward an outer periphery side, and having an annular shape around the axis line, the elastic body portion includes an end-face lip formed of a diameter reducing portion and a diameter increasing portion which is a lip having an annular shape around the axis line, the diameter reducing portion being continuously formed with a base portion which is attached to an inner peripheral end of the reinforcing ring, and having a conical tubular shape whose diameter decreases as the diameter reducing portion progresses toward one side in an axis line direction, the diameter increasing portion being continuously formed with one side of the diameter reducing portion in the axis line direction, a diameter of the diameter increasing portion increasing as the diameter increasing portion progresses toward the one side, and a distal end portion of the diameter increasing portion contacting a surface of the flange portion on another side in the axis line direction, and in the end-face lip, a length L 1  is greater than a length L 2  (L 1 &gt;L 2 ), the length L 1  being defined between a shoulder portion, connecting the base portion and the diameter reducing portion with each other, and a bent portion, connecting the diameter reducing portion and the diameter increasing portion with each other, and the length L 2  being defined between the bent portion and the distal end portion. 
     The sealing apparatus according to one aspect of the present disclosure is characterized in that, in the end-face lip, a thickness of the bent portion is smaller than a thickness of the diameter reducing portion and a thickness of the diameter increasing portion. 
     The sealing apparatus according to one aspect of the present disclosure is characterized in that the surface of the flange portion of the slinger on the other side has at least one groove. 
     In such a state, it is preferable that a no-load contact region has no groove or has the groove with a depth of 10 μm or less, the no-load contact region being a region of the flange portion which the distal end portion contacts in a state where a pressure difference between spaces separated by the end-face lip and the flange portion of the slinger is zero, and a negative pressure contact region has the groove, the negative pressure contact region being a region of the flange portion which the distal end portion contacts in a state where, of the spaces separated, a pressure of a first space on a side where the bent portion bends toward an inner side is lower than a pressure in a second space on a side where the bent portion bends toward an outer side by a predetermined pressure difference or more and, due to the pressure difference, the distal end portion moves toward a first space side on a surface of the flange portion. 
     It is also preferable that, in the flange portion, a positive pressure contact region has the groove, the positive pressure contact region being a region on a side opposite to the negative pressure contact region with the no-load contact region interposed between the positive pressure contact region and the negative pressure contact region. 
     Effects of Disclosure 
     According to the present disclosure, it is possible to provide a sealing apparatus having improved sealing performance when a negative pressure is generated on the side of the object to be sealed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view on a cross section along an axis line for illustrating a schematic configuration of a sealing apparatus according to an embodiment of the present disclosure. 
         FIG. 2  is a partially enlarged cross-sectional view illustrating, in an enlarged manner, a part of the cross section along the axis line for illustrating the schematic configuration of the sealing apparatus illustrated in  FIG. 1 . 
         FIG. 3  is a view of a slinger of the sealing apparatus illustrated in  FIG. 1  seen from an outer side. 
         FIG. 4  is a partially enlarged cross-sectional view of the sealing apparatus in a usage state where the sealing apparatus according to an embodiment of the present disclosure is attached to a housing and a shaft inserted into a shaft hole. 
         FIG. 5  is a partially enlarged cross-sectional view of a sealing apparatus body of the sealing apparatus in the usage state illustrated in  FIG. 4 , the view illustrating a state where there is no pressure difference between a side of an object to be sealed and the outer side. 
         FIG. 6  is a partially enlarged cross-sectional view of the sealing apparatus body in the usage state of the sealing apparatus illustrated in  FIG. 5 , the view illustrating a state where the side of the object to be sealed has a negative pressure with respect to the outer side. 
         FIG. 7  is a partially enlarged cross-sectional view of the sealing apparatus body in the usage state of the sealing apparatus illustrated in  FIG. 5 , the view illustrating a state where the side of the object to be sealed has a positive pressure with respect to the outer side. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a sealing apparatus according to an embodiment of the present disclosure will be described with reference to drawings. 
     In the following description, for the purpose of illustration, a direction of an arrow a (see  FIG. 1 ) in an axis line x direction is set as an inner side, and a direction of an arrow b (see  FIG. 1 ) in the axis line x direction is set as an outer side. More specifically, the inner side is a side of space to be sealed (side of an object to be sealed) and a side of space where an object to be sealed such as a lubricant exists, and the outer side is an opposite side of the inner side. Further, in a direction perpendicular to the axis line x (hereinafter, also referred to as a “radial direction”), a direction away from the axis line x (a direction of an arrow c in  FIG. 1 ) is set as an outer periphery side, and a direction approaching the axis line x (a direction of an arrow d in  FIG. 1 ) is set as an inner periphery side. 
       FIG. 1  is a cross-sectional view on a cross section along the axis line x for illustrating a schematic configuration of a sealing apparatus  1  according to the embodiment of the present disclosure. Further,  FIG. 2  is a partially enlarged cross-sectional view illustrating, in an enlarged manner, a part of the cross section along the axis line x for illustrating the schematic configuration of the sealing apparatus  1 . The configuration of the sealing apparatus  1  according to the present embodiment will be described with reference to  FIG. 1  and  FIG. 2 . The sealing apparatus  1  according to the present embodiment is a sealing apparatus for sealing a gap having an annular shape and formed between a shaft not illustrated in the drawing and a hole (shaft hole) not illustrated in the drawing of a housing into which this shaft is to be inserted. The sealing apparatus  1  is used to seal a gap formed between this shaft and the shaft hole which is formed in the housing or the like, and into which this shaft is to be inserted in a vehicle or a general-purpose machine. For example, the sealing apparatus  1  is used to seal a space having an annular shape and formed between a crank shaft of an engine and a crank hole, which is a shaft hole formed in a front cover or a cylinder block and a crank case. Note that objects to which the sealing apparatus  1  according to the embodiment of the present disclosure may be applied are not limited to the above. 
     The sealing apparatus  1  according to the present embodiment includes a sealing apparatus body  2  to be fitted into a hole, and a slinger  3  to be attached to a shaft. The sealing apparatus body  2  includes a reinforcing ring  10  having an annular shape around the axis line x, and an elastic body portion  20  which is formed of an elastic body attached to the reinforcing ring  10 , and which has an annular shape around the axis line x. The slinger  3  includes a flange portion  31  which is a portion extending toward the outer periphery side and having an annular shape around the axis line x. The elastic body portion  20  includes an end-face lip  21  which is a lip extending toward one side in the axis line x direction, contacting the flange portion  31  from another side in the axis line x direction, and having an annular shape around the axis line x. Hereinafter, the structure of the sealing apparatus  1  will be specifically described. 
     Between the housing and the shaft, the inner side of the sealing apparatus  1  is a side of an object to be sealed (a side where a first space which will be described later is formed). On the inner side, a liquid, such as an engine oil, for example, exists as the object to be sealed. The sealing apparatus  1  provides sealing in the shaft hole of the housing such that this liquid on the inner side is prevented from leaking to the outer side while insertion of the shaft through the sealing apparatus  1  is allowed. 
     As illustrated in  FIG. 1  and  FIG. 2 , in the sealing apparatus body  2 , the reinforcing ring  10  is a member which is made of metal and which has an annular shape centered on or substantially centered on the axis line x. The reinforcing ring  10  is formed so that the sealing apparatus body  2  is press-fitted, engaged and fitted into the shaft hole of the housing which will be described later. The reinforcing ring  10  includes, for example, a tubular portion  11  which is a portion located on the outer periphery side and having a tubular shape, a disk portion  12  which is a portion extending from an end portion on the outer side of the tubular portion  11  toward the inner periphery side, and having a hollow disk shape, a conical ring portion  13  which is an annular portion extending from an end portion on the inner periphery side of the disk portion  12  toward the inner side and the inner periphery side, and having a conical shape, and a disk portion  14  which is a portion extending in a radial direction from an end portion on the inner side or the inner periphery side of the conical ring portion  13  toward the inner periphery side, reaching an end portion (inner peripheral end  14   a ) on the inner periphery side of the reinforcing ring  10 , and having a hollow disk shape. More specifically, the tubular portion  11  of the reinforcing ring  10  includes an outer periphery side cylindrical portion  11   a  which is a portion located on the outer periphery side and having a cylindrical shape or a substantially cylindrical shape, an inner periphery side cylindrical portion  11   b  which is a portion extending on the outer side and the inner periphery side of the outer periphery side cylindrical portion  11   a  and having a cylindrical shape or a substantially tubular shape, and a connecting portion  11   c  which is a portion connecting the outer periphery side cylindrical portion  11   a  and the inner periphery side cylindrical portion  11   b . The outer periphery side cylindrical portion  11   a  of the tubular portion  11  is fitted into the shaft hole so that, when the sealing apparatus body  2  is fitted into the shaft hole of the housing which will be described later, the axis line x of the sealing apparatus body  2  matches an axis line of the shaft hole. The elastic body portion  20  is attached to the reinforcing ring  10  from a substantially outer periphery side and an outer side so as to reinforce the elastic body portion  20 . 
     The slinger  3  includes the flange portion  31  which is a portion extending toward the outer periphery side (the direction of the arrow c) and having an annular shape around the axis line x. On another side (outer side) of the flange portion  31  of the slinger  3 , at least one thread groove  33  is formed on the inner periphery side of a lip contact portion  32 , which is a portion where the slinger  3  contacts the end-face lip  21 . 
     As illustrated in  FIG. 1  and  FIG. 2 , the elastic body portion  20  includes a base portion  25  which is a portion attached to a portion at an end on the inner periphery side of the disk portion  14  of the reinforcing ring  10 , a gasket portion  26  which is a portion attached to the tubular portion  11  of the reinforcing ring  10  from the outer periphery side, and a rear cover portion  27  which is a portion attached to the reinforcing ring  10  between the base portion  25  and the gasket portion  26  from the outer side. More specifically, as illustrated in  FIG. 2 , the gasket portion  26  is attached to the inner periphery side cylindrical portion  11   b  of the tubular portion  11  of the reinforcing ring  10 . Further, an outer diameter of the gasket portion  26  is greater than an outer diameter of the outer periphery side cylindrical portion  11   a  of the reinforcing ring  10 . Therefore, when the sealing apparatus body  2  is fitted into the shaft hole which will be described later, the gasket portion  26  is compressed in the radial direction between the inner periphery side cylindrical portion  11   b  of the reinforcing ring  10  and the shaft hole, thus providing sealing between the shaft hole and the inner periphery side cylindrical portion  11   b  of the reinforcing ring  10 . By this means, space between the sealing apparatus body  2  and the shaft hole is sealed. The outer diameter of the gasket portion  26  may not be greater than the outer diameter of the outer periphery side cylindrical portion  11   a  of the reinforcing ring  10  over the whole axis line x direction. The outer diameter of the gasket portion  26  may be partially greater than the outer diameter of the outer periphery side cylindrical portion  11   a  of the reinforcing ring  10 . For example, a surface on the outer periphery side of the gasket portion  26  may have a protruding portion having an annular shape and having a diameter of a distal end of the protruding portion greater than the outer diameter of the outer periphery side cylindrical portion  11   a  of the reinforcing ring  10 . 
     Further, the end-face lip  21  of the elastic body portion  20  extends from the base portion  25  toward the inner side (the direction of the arrow a) in an annular shape centered on or substantially centered on the axis line x. The end-face lip  21  is formed so that, in a usage state of the sealing apparatus  1  described later where the sealing apparatus  1  is attached to a desired position of an attachment object, a distal end portion  21   a  contacts the flange portion  31  of the slinger  3  from the outer side with a predetermined interference (a slinger contact portion  23 ). The base portion  25  has a projecting portion  25   a  which projects in an annular shape toward the inner side (the direction of the arrow a) in the axis line x direction, and the projecting portion  25   a  is continuously formed with the end-face lip  21 . 
     The projecting portion  25   a  projects from the base portion  25  toward the inner side (the direction of the arrow a) in the axis line x direction. However, the projecting direction is not limited. For example, the projecting portion  25   a  may project from the base portion  25  toward the inner periphery side (the direction of the arrow d), or may project in an oblique direction between the inner side (the direction of the arrow a) and the inner periphery side (the direction of the arrow d). Further, the projecting portion  25   a  is not an essential component. Accordingly, it may be configured such that the projecting portion  25   a  has an extremely small length, or no projecting portion  25   a  is provided so that the projecting portion  25   a  cannot be distinguished from a shoulder portion  21   e  which will be described later. 
     The end-face lip  21  includes a diameter reducing portion  21   d  having a conical tubular shape whose diameter decreases as the diameter reducing portion  21   d  progresses toward the inner side (the direction of the arrow a) in the axis line x direction, and a diameter increasing portion  21   b  which is continuously formed with the inner side (the direction of the arrow a) of the diameter reducing portion  21   d  in the axis line x direction, and which has a conical tubular shape whose diameter increases as the diameter increasing portion  21   b  progresses toward the inner side (the direction of the arrow a). The diameter increasing portion  21   b  reaches the distal end portion  21   a.    
     The projecting portion  25   a  and the diameter reducing portion  21   d  are connected with each other via the shoulder portion  21   e . Further, the diameter reducing portion  21   d  and the diameter increasing portion  21   b  are connected with each other via a bent portion  21   c.    
     That is, as illustrated in  FIG. 1  and  FIG. 2 , the end-face lip  21  is configured as follows. In cross section along the axis line x (hereinafter, also simply referred to as “cross section”), the end-face lip  21  projects from the base portion  25  toward the inner side at the projecting portion  25   a , changes the direction toward the inner side and the inner periphery side at the shoulder portion  21   e , and extends obliquely with respect to the axis line x at the diameter reducing portion  21   d . Thereafter, the end-face lip  21  changes the direction toward the inner side and the outer periphery side at the bent portion  21   c , and extends obliquely with respect to the axis line x at the diameter increasing portion  21   b , and the distal end portion  21   a  of the end-face lip  21  contacts the flange portion  31  of the slinger  3  from the outer side. 
     As illustrated in  FIG. 1  and  FIG. 2 , in cross section, the shoulder portion  21   e  connects the projecting portion  25   a  and the diameter reducing portion  21   d  with a predetermined curvature (R), the projecting portion  25   a  and the diameter reducing portion  21   d  having different angles. As illustrated in  FIG. 1  and  FIG. 2 , in cross section, the bent portion  21   c  is formed of a bent portion having a predetermined length and a linear shape, and portions formed on both sides of the bent portion and having curvatures. The bent portion deflects and the portions having curvatures are also bend so that the bent portion  21   c  connects the diameter reducing portion  21   d  and the diameter increasing portion  21   b  with each other, the diameter reducing portion  21   d  and the diameter increasing portion  21   b  having different angles. 
     In cross section illustrated in  FIG. 4 , a length L 1  of the diameter reducing portion  21   d  is greater than a length L 2  of the diameter increasing portion  21   b . In other words, the length L 1  defined between the shoulder portion  21   e  and the bent portion  21   c  is greater than the length L 2  defined between the bent portion  21   c  and the distal end portion  21   a  (L 1 &gt;L 2 ). In such a state, points which become references for the shoulder portion  21   e  and the bent portion  21   c  are bending points where the end-face lip  21  is folded back at the angle of the shoulder portion  21   e  and the bent portion  21   c , and such points are also points (a shoulder portion reference point  21   ep  and a bent portion reference point  21   cp ) forming apexes of included angles which vary when the included angle of the shoulder portion  21   e  and the included angle of the bent portion  21   c  are varied by causing the distal end portion  21   a  to slide toward the inner periphery side and the outer periphery side against an outer side surface  31   d  of the flange portion  31  (indicating that the distal end portion  21   a  is moved to have a state illustrated in  FIG. 7  from a state illustrated in  FIG. 6  which will be described later via a state illustrated in  FIG. 5  and, further, the distal end portion  21   a  is moved in the opposite direction). Although the portion to be bent has a large length, the apex of the included angle of the portion to be bent is fixed at one point, and the bent portion reference point  21   cp  is disposed at substantially the center of the portion to be bent. 
     As illustrated in  FIG. 2 , the end-face lip  21  is configured such that a thickness of the bent portion  21   c  is smaller than a thickness of the diameter reducing portion  21   d  and a thickness of the diameter increasing portion  21   b . In a free state before the sealing apparatus  1  is assembled, the included angle at the bent portion reference point  21   cp  of the bent portion  21   c  is larger. Accordingly, when the slinger  3  is attached to the sealing apparatus body  2  with a predetermined interference, the included angle at the bent portion reference point  21   cp  is reduced. Therefore, a reaction force resulting from the reduction in the included angle causes the distal end portion  21   a  to contact the outer side surface  31   d  of the flange portion  31  such that the distal end portion  21   a  pushes against the outer side surface  31   d  of the flange portion  31 . Setting the thickness of the bent portion  21   c  smaller than the thicknesses of other portions can reduce a reaction force at the bent portion  21   c  so that it is possible to suppress an increase in torque when the sealing apparatus is used. 
     The above-described reinforcing ring  10  is formed of a metal material, and examples of this metal material can include, for example, stainless steel and SPCC (cold rolled steel sheet). Further, examples of the elastic body of the elastic body portion  20  can include, for example, various kinds of rubber materials. The various kinds of rubber materials can include, for example, synthetic rubber such as nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), acryl rubber (ACM), and fluorine-containing rubber (FKM). 
     The reinforcing ring  10  is manufactured through, for example, press work or forging, and the elastic body portion  20  is molded through cross-linking (vulcanization) molding using a mold. Upon this cross-linking molding, the reinforcing ring  10  is disposed in the mold, and the elastic body portion  20  is caused to adhere to the reinforcing ring  10  through cross-linking adhesion so that the elastic body portion  20  and the reinforcing ring  10  are integrally molded. 
     The slinger  3  is a member having an annular shape and to be attached to the shaft when the sealing apparatus  1  is in the usage state which will be described later. The slinger  3  is a member having an annular shape centered on or substantially centered on the axis line x. The slinger  3  has a cross section having a substantially L shape, and includes the flange portion  31 , and a tubular portion  34  which is connected to an end portion on the inner periphery side of the flange portion  31 , which extends in the axis line x direction, and which has a tubular shape or a substantially tubular shape. 
     The flange portion  31  specifically includes an inner periphery side disk portion  31   a  in a hollow disk shape or a substantially hollow disk shape which extends from the tubular portion  34  in the radial direction, an outer periphery side disk portion  31   b  in a hollow disk shape or a substantially hollow disk shape which expands on the outer periphery side of the inner periphery side disk portion  31   a  and which extends in the radial direction, and a connecting portion  31   c  which connects an end portion on the outer periphery side of the inner periphery side disk portion  31   a  and an end portion on the inner periphery side of the outer periphery side disk portion  31   b . The outer periphery side disk portion  31   b  is located on the outer side of the inner periphery side disk portion  31   a  in the axis line x direction. Note that the shape of the flange portion  31  is not limited to the above-described shape, and may be any of various shapes in accordance with an application object. For example, the flange portion  31  may not include the inner periphery side disk portion  31   a  and the connecting portion  31   c , and the outer periphery side disk portion  31   b  may extend to the tubular portion  34 , and may be connected to the tubular portion  34 , thus forming a portion in a hollow disk shape or a substantially hollow disk shape which extends from the tubular portion  34  in the radial direction. 
     The lip contact portion  32  of the flange portion  31  where the end-face lip  21  contacts is formed on the outer side surface  31   d  of the outer periphery side disk portion  31   b  which is a surface facing the outer side. It is preferable that the outer side surface  31   d  is a surface extending along a plane expanding in the radial direction. 
       FIG. 3  is a view of the slinger  3  of the sealing apparatus  1  seen from the outer side. As illustrated in  FIG. 3 , the thread groove  33  formed of a recessed portion which is recessed toward the inner side is formed on the outer side surface  31   d  of the flange portion  31 . The thread groove  33  ranges from the inner periphery side to the outer periphery side. To be more specific, the thread groove  33  has a spiral shape and, as will be described later, a region  32   a  where no thread groove  33  is formed is present at an intermediate portion of the range from the inner periphery side to the outer periphery side. With the provision of this thread groove  33 , an air flow which flows toward the outer periphery side can be formed when the slinger  3  is rotated, thus causing a pumping action. On the outer side surface  31   d  of the flange portion  31 , the thread groove  33  is located on the inner periphery side of the lip contact portion  32 . For example, the thread groove  33  having multiple threads is formed on the outer side surface  31   d  of the flange portion  31 . The number of thread grooves  33  and a shape along which the thread groove  33  extends are not limited to the above. For example, the thread groove  33  has a shape along a line drawn on a plane orthogonal to an axis line of a conical surface when a thread groove formed on this conical surface and having a spiral shape is projected on this plane. 
     Further, in the present embodiment, as illustrated in  FIG. 3 , on the outer side surface  31   d  of the flange portion  31 , no thread groove  33  is present in the region  32   a  (“no-load contact region  32   a ” which will be described later) which is separated from the axis line x by a predetermined distance and which has an annular shape. As will be described later, this region  32   a  where no thread groove  33  is present is a region of the flange portion  31  which the distal end portion  21   a  of the end-face lip  21  contacts when there is no pressure difference between spaces separated by the diameter increasing portion  21   b  of the end-face lip  21  and the flange portion  31  of the slinger  3 . The thread groove  33  is formed in a region (“a negative pressure contact region  32   h ” which will be described later) on the outer periphery side of the region  32   a  and in a region (“positive pressure contact region  32   c ” which will be described later=a region on the side opposite to the negative pressure contact region  32   b  with the no-load contact region  32   a  interposed therebetween) on the inner periphery side of the region  32   a . The negative pressure contact region  32   b  and the positive pressure contact region  32   c  are divided by the no-load contact region  32   a.    
     The depth of this thread groove  33  may be appropriately selected, and is selected from a range from approximately 40 to 100 μm, for example. 
     As illustrated in  FIG. 2 , the tubular portion  34  of the slinger  3  includes a cylindrical portion  35 , which is a portion at least partially having a cylindrical shape or a substantially cylindrical shape. This cylindrical portion  35  is formed so as to be able to be fitted on the shaft. That is, an inner diameter of the cylindrical portion  35  is smaller than a diameter of the outer peripheral surface of the shaft so that the cylindrical portion  35  can be interference-fitted at the shaft. The slinger  3  is not limited to a part fixed by the cylindrical portion  35  being interference-fitted at the shaft, and may be fixed at the shaft through adhesion by the tubular portion  34 , or may be fixed at the shaft using other publicly known fixing method. Note that the whole tubular portion  34  may be formed of the cylindrical portion  35 . 
     The slinger  3  is made using a metal material and, for example, made using stainless steel excellent in rust resistance and rust-proofness. When the slinger  3  is made using stainless steel, it is possible to suppress occurrence of rust at the lip contact portion  32 , which is a sliding portion against the end-face lip  21 , so that it is possible to maintain a sealing function and sealing performance of the end-face lip  21  for a long period of time. It is also possible to suppress that occurrence of rust changes the shape of the thread groove  33 . Therefore, it is possible to suppress the reduction in pumping effect which is exerted by the thread groove  33 . The material for forming the slinger  3  is not limited to stainless steel, and the slinger  3  may be made using other metals. Note that it is preferable that rust-proofing, such as rust-proofing plating, is performed on the surface of the slinger  3 , particularly on the lip contact portion  32 . 
     Action of the sealing apparatus  1  having the above-described configuration will be described next. 
       FIG. 4  is a partially enlarged cross-sectional view of the sealing apparatus  1  in a usage state where the sealing apparatus  1  is attached to a housing  50 , which is an attachment object, and to a shaft  52  inserted into a shaft hole  51 , which is a through hole formed in the housing  50 . The housing  50  may be, for example, a front cover of an engine, or a cylinder block and a crank case, and the shaft hole  51  may be a crank hole formed in the front cover, or the cylinder block and the crank case. Further, the shaft  52  may be, for example, a crank shaft. 
     As illustrated in  FIG. 4 , when the sealing apparatus  1  is in the usage state, the sealing apparatus body  2  is fitted into the shaft hole  51  by being press-fitted into the shaft hole  51 , and the slinger  3  is attached to the shaft  52  by being interference-fitted at the shaft  52 . More specifically, the outer periphery side cylindrical portion  11   a  of the reinforcing ring  10  contacts an inner peripheral surface  51   a  of the shaft hole  51 , so that an axis of the sealing apparatus body  2  is made to match an axis of the shaft hole  51 . Further, the gasket portion  26  of the elastic body portion  20  tightly contacts the inner peripheral surface  51   a  of the shaft hole  51  by the gasket portion  26  being compressed in the radial direction between the inner peripheral surface  51   a  of the shaft hole  51  and the inner periphery side cylindrical portion  11   b  of the reinforcing ring  10 , so that sealing between the sealing apparatus body  2  and the shaft hole  51  is realized. Further, the cylindrical portion  35  of the slinger  3  is press-fitted on the shaft  52 , and an inner peripheral surface  35   a  of the cylindrical portion  35  tightly contacts an outer peripheral surface  52   a  of the shaft  52 , so that the slinger  3  is fixed at the shaft  52 . 
     When the sealing apparatus  1  is in the usage state, relative positions between the sealing apparatus body  2  and the slinger  3  in the axis line x direction are determined so that the slinger contact portion  23  of the end-face lip  21  of the elastic body portion  20  contacts the lip contact portion  32 , the slinger contact portion  23  being a portion on a distal end portion  21   a  side of an inner peripheral surface  22 , and the lip contact portion  32  being a portion on the outer side surface  31   d  of the outer periphery side disk portion  31   b  of the flange portion  31  of the slinger  3 . 
       FIG. 5  illustrates a partially enlarged cross-sectional view of the sealing apparatus body  2  of the sealing apparatus  1  in the usage state illustrated in  FIG. 4 . In  FIG. 5 , the slinger  3  is indicated by a chain line. Further, in  FIG. 5 , the shape of the end-face lip  21  in the free state before the sealing apparatus  1  is assembled is indicated by a dotted line. 
     In the state illustrated in  FIG. 5 , of the spaces separated by the end-face lip  21  and the flange portion  31  of the slinger  3 , a pressure in a first space S 1  on a side where the bent portion  21   c  is bent toward the inner side (the side of the object to be sealed, inner side) is equal to a pressure in a second space S 2  on a side where the bent portion  21   c  is bent toward the outer side (outer side) (there is no pressure difference), and both sides are at atmospheric pressure. In this state, the distal end portion  21   a  of the end-face lip  21  contacts the outer side surface  31   d  of the flange portion  31  in the no-load contact region  32   a.    
     For example, when an engine is operated so that the shaft  52  starts to be rotated, the inside of the crank case of the engine is held at a negative pressure for environmental protection. Accordingly, a pressure on the side of the object to be sealed, that is, the pressure in the first space S 1 , is reduced, thus having a negative pressure state and hence, the pressure in the first space S 1  becomes lower than the pressure in the second space S 2 . Therefore, the end-face lip  21  is attracted toward the first space S 1  side due to a pressure difference. When a pressure difference between both spaces becomes a predetermined value or more, as illustrated in  FIG. 6 , the distal end portion  21   a  of the end-face lip  21  contacts the outer side surface  31   d  of the flange portion  31  while moving to the negative pressure contact region  32   b .  FIG. 6  is a partially enlarged cross-sectional view of the sealing apparatus body  2  in the usage state of the sealing apparatus  1  illustrated in  FIG. 5 , and  FIG. 6  illustrates a state where the pressure in the first space S 1  (side of the object to be sealed) is lower than the pressure in the second space S 2  (outer side) (a state where a negative pressure is generated in the first space S 1 ). 
     When the end-face lip  21  is attracted toward the first space S 1  side by the negative pressure, the entire end-face lip  21  is attracted. The end-face lip  21  is observed for respective portions. In the diameter increasing portion  21   b , a pressure difference (negative pressure) acts, using the bent portion  21   c  as a base point, in a direction toward the outer side (the direction of the arrow b), that is, in a direction along which the distal end portion  21   a  is separated from the outer side surface  31   d  of the flange portion  31 . In the diameter reducing portion  21   d , a pressure difference (negative pressure) acts, using the shoulder portion  21   e  as a base point, in a direction toward the inner side (the direction of the arrow a), that is, in a direction along which the distal end portion  21   a  is pushed against the outer side surface  31   d  of the flange portion  31 . 
     As has been described above, the length L 1  of the diameter reducing portion  21   d  is greater than the length L 2  of the diameter increasing portion  21   b  (L 1 &gt;L 2 ). Accordingly, the action toward the inner side (the direction of the arrow a) at the diameter reducing portion  21   d  is dominant to the action toward the outer side (the direction of the arrow b) at the diameter increasing portion  21   b . As a result, in the state illustrated in  FIG. 6 , the distal end portion  21   a  is pushed against the outer side surface  31   d  of the flange portion  31  by an action of a negative pressure. Therefore, in the sealing apparatus  1  of the present embodiment, an object to be sealed is prevented from easily leaking even in a negative pressure state and hence, it is possible to improve sealing performance when a negative pressure is generated on the side of the object to be sealed. Further, the diameter increasing portion  21   b  contacts the outer side surface  31   d  of the flange portion  31  at the distal end portion  21   a  in the same direction as a normal end-face lip and hence, there is no possibility that a function as the end-face lip is impaired. 
     Provided that the size relationship between the length L 1  of the diameter reducing portion  21   d  and the length L 2  of the diameter increasing portion  21   b  satisfies L 1 &gt;L 2 , the above-described action and advantageous effect can be expected. However, an extremely small difference between L 1  and L 2  weakens, during a negative pressure state, an action of pushing the distal end portion  21   a  against the outer side surface  31   d  of the flange portion  31 , the action being caused by the diameter reducing portion  21   d . On the other hand, an extremely small length L 2  with respect to the length L 1  weakens a lip effect, which is the original effect of the end-face lip  21 . Accordingly, it is desirable that L 2  is appropriately smaller than L 1 . 
     On the outer side surface  31   d  of the flange portion  31  of the slinger  3 , the thread groove  33 , which forms multiple threads, is formed in the negative pressure contact region  32   b  where the distal end portion  21   a  of the end-face lip  21  is located in the state illustrated in  FIG. 6 . When the slinger  3  is rotated, the thread groove  33  forms an air flow which flows toward the outer periphery side. Due to this air flow which is generated by the rotation of the thread groove  33  (the slinger  3 ), a pumping action is generated in a region in the vicinity of the slinger contact portion  23  and the lip contact portion  32 . Due to this pumping action, even when an object to be sealed leaks from the first space S 1  side (the side of the object to be sealed) to the second space S 2  side (outer side), the leaked object to be sealed is caused to get over the slinger contact portion  23  and the lip contact portion  32  to return to the first space S 1  side (the side of the object to be sealed). As described above, due to a pumping action generated by the thread groove  33  formed on the flange portion  31  of the slinger  3 , it is possible to suppress leakage of the object to be sealed to the second space S 2  side (outer side). 
     Whereas, during a static state where a driving device, such as an engine, is not operated, pressure reduction on the side of the object to be sealed, that is, pressure reduction in the first space S 1 , is released so that the first space S 1  is brought into an atmospheric pressure state, thus bringing about a state where there is no pressure difference between the first space S 1  and the second space S 2 , that is, the state illustrated in  FIG. 5 . In the state illustrated in  FIG. 5 , the distal end portion  21   a  of the end-face lip  21  contacts the outer side surface  31   d  of the flange portion  31  in the no-load contact region  32   a . The no-load contact region  32   a  has no thread groove  33 . Therefore, according to the sealing apparatus of the present embodiment, it is possible to solve the problem of leakage in a static state. 
     In the present embodiment, the no-load contact region  32   a  has no thread groove  33 . However, the no-load contact region  32   a  may have a groove with an extremely shallow depth, for example, a groove having a depth of 10 μm or less. The groove with an extremely shallow depth of up to approximately 10 μm does not easily cause leakage in a static state. Further, in the case where the groove with an extremely shallow depth is provided to the no-load contact region  32   a  as described above, even when an operation is performed in a state where there is no pressure difference between the first space S 1  and the second space S 2 , a pumping action caused by the groove can be expected. Accordingly, it is possible to suppress leakage of the object to be sealed to the second space S 2  side (outer side). 
     In the case where the groove with an extremely shallow depth up to approximately 10 μm is provided to the no-load contact region  32   a , it is preferable that the number of threads of the groove is set to a large number. The appropriate number of threads in an actual operation differs depending on the depth of the groove. Accordingly, it is sufficient to select the appropriate number of threads by observing a situation of leakage in a static state and leakage of the object to be sealed during operation. 
     Depending on the operation state of the engine, there may be a case where a positive pressure is suddenly generated in the crank case of the engine. In such a case, a pressure is applied to the side of the object to be sealed, that is, the first space S 1 , so that the pressure in the first space S 1  becomes higher than the pressure in the second space S 2 . In such a case, the end-face lip  21  is pushed toward the second space S 2  side due to the pressure difference. Further, when a pressure difference between both spaces becomes a predetermined value or more, as illustrated in  FIG. 7 , the distal end portion  21   a  of the end-face lip  21  contacts the outer side surface  31   d  of the flange portion  31  while moving to the positive pressure contact region  32   c .  FIG. 7  is a partially enlarged cross-sectional view of the sealing apparatus body  2  in the usage state of the sealing apparatus  1  illustrated in  FIG. 5 , and  FIG. 7 , and illustrates a state where the pressure in the first space S 1  (the side of the object to be sealed) is higher than the pressure in the second space S 2  (outer side) (a state where a positive pressure is generated in the first space S 1 ). 
     When the end-face lip  21  is pushed toward the second space S 1  side by a positive pressure, the entire end-face lip  21  is pushed. The end-face lip  21  is observed for respective portions. In the diameter increasing portion  21   b , a pressure difference (positive pressure) acts, using the bent portion  21   c  as a base point, in a direction toward the inner side (the direction of the arrow a), that is, in a direction along which the distal end portion  21   a  is pushed against the outer side surface  31   d  of the flange portion  31 . On the other hand, in the diameter reducing portion  21   d , a pressure difference (negative pressure) acts, using the shoulder portion  21   e  as a base point, in a direction along which the bent portion  21   c  is moved toward outer side (the direction of the arrow b). As can be understood from  FIG. 7 , this movement of the diameter reducing portion  21   d  acts not in a direction along which the distal end portion  21   a  is separated from the outer side surface  31   d  of the flange portion  31 , but in a direction along which the distal end portion  21   a  is pushed against the outer side surface  31   d  of the flange portion  31 . As a result, in the state illustrated in  FIG. 7 , the distal end portion  21   a  is pushed against the outer side surface  31   d  of the flange portion  31  due to the action of a positive pressure. Therefore, in the sealing apparatus  1  of the present embodiment, the object to be sealed is prevented from easily leaking even in a positive pressure state, and there is no possibility that sealing performance is impaired when a positive pressure is generated on the side of the object to be sealed. 
     On the outer side surface  31   d  of the flange portion  31  of the slinger  3 , the thread groove  33 , which forms multiple threads, is formed in the positive pressure contact region  32   c  where the distal end portion  21   a  of the end-face lip  21  is located in the state illustrated in  FIG. 7 . Therefore, in the same manner as the state illustrated in  FIG. 6  where the distal end portion  21   a  is located in the negative pressure contact region  32   b , in the sealing apparatus  1  of the present embodiment, also in a positive pressure state, due to a pumping action generated by the thread groove  33  formed on the flange portion  31  of the slinger  3 , it is possible to suppress leakage of the object to be sealed to the second space S 2  side (outer side). 
     The embodiment of the present disclosure has been described heretofore. However, the present disclosure is not limited to the sealing apparatus  1  according to the above-described embodiment of the present disclosure, and includes any mode which falls within the concept and Claims of the present disclosure. Further, the respective components may be selectively combined as desired to solve or provide at least part of the above-described problems or effects. For example, the shape, the material, the arrangement, the size and the like of the respective components in the above-described embodiment may be suitably changed depending on a specific use mode of the present disclosure. 
     As described above, the shape of the thread groove  33  of the slinger  3  is not limited to a thread shape illustrated in  FIG. 3 , and may be any of other shapes. 
     In the present embodiment, the elastic body portion  20  does not include other lips, such as a dust lip and an intermediate lip. However, these lips may be provided to space on the inner periphery side of the base portion  25 , for example. 
     In general, the dust lip is a lip which extends from the base portion  25  toward the axis line x. The dust lip is a member where the distal end portion of the dust lip is formed to contact the cylindrical portion  35  of the slinger  3  from the outer periphery side and, in a usage state, the dust lip prevents intrusion of foreign substances, such as dust and moisture, into the sealing apparatus  1  from the outer side, which is the side opposite to the side of the object to be sealed. 
     In general, the intermediate lip is a lip which extends from the base portion  25  toward the inner side. The intermediate lip extends from the base portion  25  in an annular shape centered on or substantially centered on the axis line x, and forms a recessed portion between the intermediate lip and the base portion  25 , the recessed portion having an annular shape, and being open toward the inner side. In the usage state, there may be a case where the object to be sealed gets over the slinger contact portion  23 , which contacts the slinger  3  of the end-face lip  21 , and leaks in the inside. The intermediate lip is formed to cause this leaked object to be sealed to be stored in the recessed portion formed between the intermediate lip and the base portion  25  in such a case. 
     To cope with leakage of an object to be sealed in a negative pressure state, it is desirable to provide other lips, such as the dust lip and the intermediate lip. However, according to the present embodiment, it is possible to omit or simplify these other lips. When these other lips are omitted or simplified so that it becomes unnecessary to cause these other lips to slide against the slinger  3 , not only that the apparatus can be simplified, but also that short lifespan of the lip caused by sliding, and an increase in torque can be avoided. 
     Further, while description is provided that the sealing apparatus  1  according to the present embodiment is applied to a crank hole of an engine, an application object of the sealing apparatus according to the present disclosure is not limited to this, and the present disclosure can be applied to all configurations which can utilize the effects provided by the present disclosure, such as other vehicles, general-purpose machine and industrial machine.