Abstract:
A sealing device formed to seal between a fixed side member and a rotating side member, comprising a slinger having a fitting cylindrical part fitted to the rotating side member and a flange part formed at one end part of the fitting cylindrical part positioned on the outer side of a sealed portion so as to be extended in the radial direction. A core comprises at least a fitting cylindrical part fitted to the fixed side member. The sealing device is characterized in that one end part of the fitting cylindrical part positioned on the outer side of the sealed portion is positioned on the sealed portion side more than the sealed portion side inner surface position of the flange part of the slinger and a part of a seal lip part is formed to be projected from near one end part of the fitting cylindrical part of the core and to be brought into elastically slidable contact with the extended end face of the slinger.

Description:
TECHNICAL FIELD 
     The present invention relates to a sealing device interposed into a necessary portion to be sealed between a stationary member and a rotary member which requires to be sealed like a bearing unit of a wheel suspension of vehicles, more particularly relates to a sealing device constructed such that a slinger is assembled with a core member for fixedly holding an elastic seal member which elastically and slidably contacts with the slinger. 
     BACKGROUND OF THE INVENTION 
     Such a sealing device has been disclosed in the following JP-A-2001-65704 (Patent Document 1) and JP-A-2003-106464 (Patent Document 2). The Patent Document 1 discloses a sealing device comprising a first sealing plate and a second sealing plate, one of them being a slinger, which have an L-shaped section and include a cylindrical wall and an upright wall (flange like portion) and a seal lip. The first and second sealing plates face each other, the tip end of the upright wall of the first sealing plate and the cylindrical wall of the second sealing plate stand face to face with a small radial gap (labyrinth), and the outer side face of the upright wall is set back inwardly from the end face of the cylindrical wall of the second sealing plate. 
     The Patent Document 2 discloses a sealing device in which the tip ends of the second dust lips (seal lip) elastically and slidably contacting with the inside of a metal ring (slinger) are disposed close so as to face each other, so that the deterioration of shrink range caused by abrasion and settling can be compensated, thereby preventing the ingress of grist and dust into a closed space formed with two dust lips. Further, FIG. 1 of the Patent Document 2 shows an example wherein a part of the second seal portion contacts with the inside of the tip end portion of the outward flange (flange like portion) of the slinger. 
     SUMMARY OF THE INVENTION 
     The sealing device of the Patent Document 1 teaches that the sealing performance can be improved by the above constitution without complicating the structure. However, because the above-mentioned labyrinth is provided, dust and water easily enter the space surrounded with the first seal plate and the second seal plate from the labyrinth to be accumulated therein. If such condition is kept for a long time that dust and water are accumulated in the space, the dust and so on move in a slidably contacting portion of the seal lip and the slinger, thereby accelerating wear of the seal lip and deteriorating the durability. 
     The sealing device of the Patent Document 2 discloses that dust and so on are prevented from entering the closed space between the second dust lips and the function of preventing the ingress of dust can be kept for a long time. However, assuming that the outer annular body of metal to be provided outside of the sealing device does not exist, the function of preventing the ingress of dust (grist and so on) is not achieved at the entrance of the space surrounded with the first sealing portion and the second sealing portion. As the result, when the dust once enters the space, it moves to the portion where the dust lip and the outward flange of the slinger elastically and slidably contact, thereby arising abrasion of the dust lip. FIG. 1 of the Patent Document 2 shows an example wherein a part of the second seal portion contacts with the inside of the tip end portion of the outward flange (flange like portion) of the slinger, as mentioned above. However, it does not describe its function nor suggest it elastically and slidably contacts. Therefore, if such prior art is applied to the sealing device of the present invention which is assembled with the slinger and the core member which fixedly holds the seal member elastically and slidably contacting with the slinger, there is still a problem of the above-mentioned durability and the improvement is highly requested. 
     The present invention is proposed in view of the above-mentioned problems and the object of the present invention is to provide a newly developed sealing device which keeps superior sealing performance and durability with a simple structure. 
     A sealing device of the present invention comprises a slinger fixedly fitted into a rotary member, a core member fixedly fitted into a stationary member, and an elastic seal member attached to the core member, the elastic seal member having a plurality of seal lip portions elastically and slidably contacting with the slinger, thereby sealing a space between the stationary member and the rotary member. It is characterized in that the slinger has a fitting cylindrical portion to be fitted into the rotary member and a flange like portion extending in its radial direction from an outer edge of the fitting cylindrical portion than a sealed portion, the core member has at least a fitting cylindrical portion to be fitted into the stationary member, an outer end of the fitting cylindrical portion than the sealed portion of the cylindrical fitting portion is positioned closer to the sealed portion than an inside line at the sealed portion side of the flange like portion of the slinger, and a part of the seal lip portion is formed so as to project out around the outer end of the fitting cylindrical portion of the core member and slidably contact with an extended end face of the slinger. 
     According to the sealing device of the present invention, the extended end face of the flange like portion may be tapered. Further, according to the sealing device of the present invention, the elastic seal member may be extended so as to enclose the outer end of the fitting cylindrical portion of the core member and has an extending portion to reach a fitting face to the stationary member, and an annular bulged area may be formed around the circumferential face of the extended portion so as to be elastically and airtightly fitted between the circumferential portion and the stationary member. Still further according to the sealing device of the present invention, a tone wheel may be integrally attached on the outer surface of the flange like portion of the slinger, and the tone wheel is magnetized in such a manner that a plurality of N poles and S poles are formed alternately in a circumferential direction, thereby constituting a magnetic encoder with a magnetic sensor fixed to the stationary member. 
     According to the objective apparatus to which the sealing device of the present invention is applied, the portions of the slinger and the core member which are positioned outside relative to the sealed portion are generally exposed to the exterior environment depending on the applied place. According to the present invention, a part of the seal lip portion is formed so as to elastically and slidably contact with the extended end face of the slinger. Therefore, there is no gap to allow earth and sand, water, dust and so on to be entered in the space surrounded with the slinger and the core member having the seal member when the members may be exposed to the exterior environment, thereby preventing acceleration of abrasion of the seal member in the space because of the ingress of dust and so on to the slidably contacting portion. Further, a part of the lip portion slidably contacts in an elastic condition with the extended end face of the slinger, so that the contacting force becomes strong and the ingress of dust can be effectively prevented. The outer end of the fitting cylindrical portion of the core member is positioned close to the sealed portion than an inside line at the sealed portion side of the flange like portion the slinger so that the flange like portion of the slinger can be largely extended in its radial direction. Therefore, when a magnetic encoder is formed by attaching a tone wheel as mentioned later, the effective detection area can be easily obtained. 
     When the extended end face of the slinger is tapered as mentioned in the present invention, the contacting area of the seal lip portion becomes large, thereby more effectively preventing the ingress of dust and being advantageous in its dimensional design. Further according to the present invention, when the annular bulged area to be elastically and airtightly fitted to the stationary member is formed around the extended portion of the elastic seal member which extends to the fitting face with the stationary member, the bulged area functions as a so-called nose portion and can absorb processing error to be elastically and airtightly fitted to the stationary member even if there arises a chamfer processing error at the entering edge of the fitting portion of the stationary member. In addition, according to the above-mentioned positional relation of the fitting cylindrical portion of the core member relative to the flange like portion of the slinger, the bulged area is to be deeply fitted into the fitting portion of the stationary member, thereby strengthen the airtightly fitted condition. 
     Still further according to the sealing device of the present invention, when a tone wheel which constitutes a magnetic encoder with a magnetic sensor fixed at the stationary side is integrally attached on the outer face of the flange like portion of the slinger, the tone wheel and the magnetic sensor simply constitute a magnetic encoder so that the rotation of the rotary member can be detected, thereby achieving a practically high value sealing device while combining this function with the above-mentioned durability. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a sectional view showing an example of a bearing unit incorporated with a sealing device of one preferable embodiment of the present invention. 
         FIG. 2  is an enlarged view of the portion “X” in  FIG. 1 . 
         FIG. 2   a  is an enlarged view of the circled portion of  FIG. 2 . 
         FIG. 3  shows the same portion as  FIG. 2  of another preferable embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The preferred embodiments of the present invention are explained hereinafter referring to the attached drawings.  FIG. 1  is a sectional view showing an example of a bearing unit incorporated with a sealing device of one preferable embodiment of the present invention,  FIG. 2  is an enlarged view of the portion “X” in  FIG. 1 , and  FIG. 3  is a view similar to  FIG. 2  showing other preferable embodiment. 
       FIG. 1  shows one embodiment of the structure in which vehicle wheels are supported for a driving shaft  1  with a ball bearing unit  2 . A tire wheel (not shown) is fixed to a hub wheel  3   a  constituting an inner ring (rotary member)  3  by means of a bolt  3   b . The reference numeral  3   c  indicates a spline hole formed in the hub wheel  3   a  and the driving shaft  1  is spline fitted in the hole  3   c  and is integrally fixed to the hub wheel  3   a , thereby transmitting the rotational drive force of the driving shaft  1  into the tire wheel via the hub wheel  3   a . The reference numeral  3   d  indicates an inner ring member, which constitutes the inner ring  3  together with the hub wheel  3   a.    
     The reference numeral  4  indicates an outer ring (stationary member) which is attached and fixed to the vehicle suspension (not shown). Two rows of rolling elements (ball)  5  . . . are interposed while being held with a retainer  5   a  between the outer ring  4  and the inner ring  3  (hub  3   a  and inner ring member  3   d ). The reference numerals A and A′ indicate seal rings for preventing leakage of lubricant agent (grease and the like) charged in the rolling portion of the rolling elements  5  . . . and for preventing ingress of waste water and dust from outside and they correspond to the sealing device of the present invention and are inserted under pressure between the outer ring  4  and the inner ring  3 . The space surrounded with the seal rings A, A′ at both sides, the inner ring  3  and the outer ring  4  constitute a sealed portion S. 
       FIG. 2  shows an enlarged view of the part “X” in  FIG. 1 . The seal ring A at vehicle body side is constructed such that a ring-like core member  6  to be fitted under pressure in the inner circumference of the outer ring  4 , an elastic seal member  7  made of an elastic material such as rubber and fixed to the core member  6 , and a slinger  8  externally fitted in the outer circumference of the inner ring member  3   d  are assembled to form a pack-seal type seal ring as shown in the figure. The slinger  8  comprises a fitting cylindrical portion  8   a  externally fixed in the outer circumference of the inner ring member  3   d  and an outward flange portion (flange-like portion)  8   b  extending from an outer edge of the fitting cylindrical portion  8   a  than the sealed portion S into the radial direction (centrifugal direction). The elastic seal member  7  has seal lip portions  7   a ,  7   b ,  7   c  which elastically and slidably contact with the inner face at the sealed portion side of the outer flange like portion  8   b , the outer circumference face of the fitting cylindrical portion  8   a  and an extended end face  8   c  of the outward flange portion  8   b  respectively. The reference numeral  7   d  indicates a garter spring to be mounted elastically and annularly into the peripheral body of the seal lip portion  7   b  in order to strengthen the elastic contacting force of the seal lip portion  7   b  into the outer circumferential face of the fitting cylindrical portion  8   a.    
     The core member  6  comprises a fitting cylindrical portion  6   a  to be internally fitted and fixed in the inner circumference of the outer wheel  4  and an inward flange portion  6   b  formed at the base portion at the sealed portion S side of the fitting cylindrical portion  6   a  extending in the radial direction (centripetal direction). The vehicle side face (outer face) of the outward flange portion  8   b  of the slinger  8  is integrally attached with the tone wheel  9  which is a magnetic rubber sheet formed by mixing magnetic powder such as ferrite in a rubber material and is magnetized so as to alternately arrange plural north poles and south poles in the circumferential direction. A magnetic sensor  10  is fixed to the vehicle side (stationary member side) in such a manner that the detecting face opposes the tone wheel  9 , thereby constituting a magnetic encoder E for detecting the rotation number (rotary speed) of vehicles together with the tone wheel  9 . 
     The core member  6  and the slinger  8  are obtained by sheet metal processing of the cold rolled steel sheet such as SPCC into the form shown in the figure. The magnetic rubber sheet constituting the seal member  7  or the tone wheel  9  is formed such that a rubber material selected from NBR, H-NBR, ACM, AEM, FKM and the like is integrally attached on the core member  6  or the slinger  8  by means of adhesive agent or at the same time of vulcanization molding to be integrated. As the rubber material for the latter, a ferrite magnetic powder or rare earth magnetic powder is mixed in advance as mentioned above. 
     An end face  6   c  opposite to the sealed portion S of the fitting cylindrical portion  6   a  of the core member  6  is formed so as to be inside (at the sealed portion side) of an inside line F at the sealed portion S side of the outward flange portion  8   b  of the slinger  8 . The elastic seal member  7  is formed so as to enclose the end face  6   c  from the inner face (the face opposite to the slinger  8 ) of the fitting cylindrical portion  6   a  of the core member  6  and extends to the outer circumference portion of the fitting cylindrical portion  6   a . An annular bulged portion  7   e  comprising a nose portion is provided for the elastic seal member  7  at the outer circumference portion. The dotted lines in the figure shows before it is elastically deformed. When the core member  6  is fitted under pressure in the inner circumference portion of the outer ring  4  together with the elastic seal member  7 , the bulged area  7   e  is elastically deformed to be airtightly fitted in the inner circumference portion of the outer ring  4 . In this case, if the chamfer processing error is caused at the inner circumferential entrance end of the outer ring  4 , such error is absorbed to be airtightly fitted into the inner circumferential portion of the outer ring  4 . 
     Among the plural seal lip portions  7   a ,  7   b ,  7   c , the seal lip portion  7   c  which elastically and slidably contacts with the extended end face  8   c  of the outward flange portion  8   b  of the slinger  8  is formed like a tongue so as to project out of the elastic seal member  7  locating in the fitting cylindrical portion  6   a  of the core member  6  directing into the slinger  8  outside of the sealed portion S. When the seal ring A is assembled, the seal lip portion  7   c  is designed to elastically contact with the extended end face  8   c  of the outward flange portion  8   b  accompanied with elastic deformation. According to the seal ring A mounted between the inner ring  3  and the outer ring  4 , the slinger  8  axially rotates around the center of the driving shaft  1  following the axial rotation of the driving shaft  1  and the inner ring  3  and the seal lip portions  7   a ,  7   b ,  7   c  slidably contact with the inner face and the extended end face  8   c  of the slinger  8  in an elastic condition. At the same time the tone wheel  9  axially rotates around the center of the driving shaft  1 , the magnetic sensor  10  detects the alternate magnetic change in the N poles and the S poles following the rotation of the tone wheel  9  and counts the pulse signals caused by the magnetic change, thereby calculating the rotary speed and so on of the driving shaft  1 , namely the tire wheel (not shown). 
     The space portion SO formed by the slinger  8  and the core member  6  with the elastic seal member  7  is closed by the seal lip portion  7   c  which is positioned at the border of the slinger  8  and the core member  6  exposed to the exterior environment, so that the space portion SO becomes a completely closed space and the grist and dust cannot be entered into the space portion SO from outside. Further the seal lip portion  7   c  is formed like a tongue so as to project toward the slinger  8  directing into the outside of the sealed portion S as mentioned above, the prevention ability for the ingress of grist and dust from outside becomes strong and the prevention function is kept for a long time. Therefore, the grist and dust do not enter the space portion SO, so that they do not enter the elastically and slidably contacting portion of the seal lip portions  7   a ,  7   b  to the inside of the slinger  8 , thereby keeping the sealing performance of the elastic seal member  7  and improving the durability. 
     The end face  6   c  of the fitting cylindrical portion  6   a  of the core member  6  is formed so as to be positioned in the inside line F of the outward flange portion  8   b  of the slinger  8 , so that the extended width of the outward flange  8   b  in a centrifugal direction can be increased as a design choice. As the result, when the tone wheel  9  is attached to the outer face of the outward flange portion  8   b  to form a magnetic encoder E as shown in the figure, the actual effective detection area of the tone wheel  9  can be easily obtained. Further, according to the above-mentioned positional relation of the end face  6   c  of the fitting cylindrical portion  6   a  relative to the outward flange portion  8   b  of the slinger  8 , the bulged area (nose portion)  7   e  is positioned into the sealed portion S side. Therefore, when the bulged area  7   e  is fitted under pressure in the inner circumference portion of the outer wheel  4 , it is to be deeply fitted in a fitting direction, thereby accomplishing strong airtight fitted condition without adversely affected by the chamfer process error at the entrance of the inner circumferential portion. 
     Embodiment 2 
     The seal ring (sealing device) B shown in  FIG. 3  is characterized in that an extended end face  8   c  of the outward flange portion  8   b  of the slinger  8  is tapered. The tapered face is designed to have gradually larger diameter from the outside into the sealed portion S. The seal lip portion  7   c  provided for the elastic seal member  7  is similarly contacted with the tapered extended end face  8   c  elastically. In this case, because the extended end face  8   c  is tapered, the elastic contacting area is practically enlarged, so that the dimension error can be absorbed to keep a preferable elastic contacting condition. Further, even when the external force caused by the grist and dust acts on the seal lip portion  7   c , the component force by the tapered face acts on the seal lip portion  7   c  as the reaction force and the elastic contacted condition of the seal lip portion  7   c  and the extended end face  8   c  is kept. Other structures and effects are the same as the above-mentioned embodiment, so the common members have the same reference numerals and their explanations are omitted here. 
     In the above-mentioned embodiments, the sealing device of the present invention is applied to the seal ring A at the vehicle side shown in  FIG. 1 , however, it goes without saying that the sealing device can be applied to the seal ring A′ at the wheel side, in which the tone wheel is not provided. Further, in the above-mentioned embodiments, the inner ring  3  is set as a rotary member and the outer ring  4  is set as a stationary member, however, they may be set vice versa, in such a case the directions of the outward flange portion  8   b  of the slinger  8  and the inward flange portion  6   b  of the core member  6  are reversed respectively, accordingly it goes without saying that the shapes of the other portions are changed in such a manner that the diameter of the tapered face is made gradually smaller into the sealed portion S. Still further according to the above-mentioned embodiments, the sealing device of the present invention is applied to a bearing unit supporting the wheel shaft of the vehicle, however, it can be applied to the other mechanism which requires sealing.