Abstract:
The purpose of the present invention is to provide a ball joint dust cover that has favorable sealing functionality and, in a low temperature environment, can suppress the occurrence of the so-called small diameter opening part opening-phenomenon, and can effectively prevent reduction in the sealing functionality of the small diameter opening part and infiltration from the outside of gravel and dust into the dust cover. In order to achieve the foregoing, provided is a ball joint dust cover made of a rubbery elastic material and provided with a one-end small diameter opening part with which a hard ring is formed integrally, wherein the hard ring is sandwiched by a retainer having a three-sided box shaped gasket.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a 371 U.S. National Stage Application of International Application No. PCT/JP2013/074806, filed on Sep. 13, 2013, and published in Japanese as WO 2014/065037 A1 on May 1, 2014. This application claims priority to Japanese Application No. 2012-235218, filed on Oct. 25, 2012. The entire disclosures of the above applications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a dust cover for a ball joint. 
         [0004]    Further, the present invention relates to a dust cover for a ball joint which is used in an automobile suspension device, and a steering device. 
         [0005]    2. Description of the Conventional Art 
         [0006]    Conventionally, as a ball joint to which a dust cover is installed for the purpose of a dust prevention and a water prevention in a ball joint coupling portion, there has been known a dust cover for a ball joint which is described in FIG. 11 (Japanese Unexamined Patent Publication No. 62-137408). 
         [0007]    In a seal structure of this kind of ball joint dust cover, a spherical head portion 200 formed in one end of a ball stud 100 is retained within a socket 300. 
         [0008]    Further, a shaft 400 in the other end of the ball stud 100 is fastened and fixed to a knuckle 500. 
         [0009]    On the other hand, a one end large-diameter opening portion 800 having an approximately C-shaped cross sectional shape of a dust cover 600 made of an elastic material is fixed and retained within an annular groove portion 310 which is formed in an outer peripheral surface of the socket 300 by an annular pressure ring 700, and the other end small-diameter opening portion 150 is retained to the shaft 400. 
         [0010]    The pressure ring 700 employs a circlip which approximately has a rectangular cross sectional shape. 
         [0011]    In this kind of conventional dust cover 600 made of the elastic material, in the case that the ball stud 100 oscillates in a state in which the ball stud 100 is inclined as shown in FIG. 11, a force extending the small-diameter opening portion 150 is applied in a side in which a film portion of the dust cover 600 made of the elastic material extends (a right side on the drawing). Therefore, there is generated a so-called mouth opening phenomenon of the small-diameter portion 150 in which a lip portion of the small-diameter opening portion 150 and the knuckle 500 is disconnected. 
         [0012]    As a result, a seal performance in the small-diameter portion 150 is lowered, and a problem that sedimentation or garbage enters into the dust cover 600 from an external portion has been brought about. 
         [0013]    Particularly, the rubber constructing the dust cover 600 made of the elastic material loses an elasticity under a low-temperature atmosphere, and a following property of the film portion is lowered in relation to an oscillating motion of the ball joint. As a result, it has been known that the mouth opening phenomenon in which the seal lip portion moves away from the shaft 400 is remarkably generated. 
         [0014]    As one of methods for taking measures to the phenomenon, there has been attempts to improve the sealing performance by fitting a retainer having an L-shaped cross section to an outer peripheral surface of the ball stud and closely attaching the dust lip provided in the small-diameter opening portion to the retainer side. However, the mouth opening phenomenon can not be sufficiently resolved. 
       SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
       [0015]    The present invention is made by taking the problem mentioned above into consideration, and an object of the present invention is to provide a dust cover for a ball joint which can suppress generation of a so-called mouth opening phenomenon in a small-diameter opening portion even under a low-temperature atmosphere, can effectively inhibit a seal performance from being lowered in the small-diameter opening portion and inhibit the sedimentation or the garbage from entering into a dust cover from an external portion, and has a good sealing performance. 
       Means for Solving the Problem 
       [0016]    A dust cover for a ball joint according to the present invention is a dust cover for a ball joint structured such that a spherical head portion formed in one end of a ball stud is retained within a socket, a shaft in the other end of the ball stud is fastened and fixed to a knuckle, a one end large-diameter opening portion is fixed and retained to an outer peripheral surface of the socket, the other end small-diameter portion having a rigid ring integrally formed therein is retained to the shaft, having a film portion which connects the one end large-diameter opening portion and the other end small-diameter opening portion, and made of a rubber-like elastic material, wherein the rigid ring approximately has a rectangular shape in its cross section, and is structured such that one end of the film portion is connected to an outer peripheral surface side of the rigid ring, and the rigid ring is exposed at least in its inner peripheral surface, a first end surface in the socket side and a second end surface in the knuckle side, the dust cover for the ball joint comprises a retainer having a cylinder portion which is fitted and fixed to the shaft outer peripheral surface and is provided with an outer peripheral surface facing to the inner peripheral surface, a first flange portion which is provided with an upper end surface facing to the first end surface, and a second flange portion which is provided with a lower end surface facing to the second end surface, and the retainer has at least two kinds of gaskets among three kinds of gaskets including a first gasket which is integrally bonded to the outer peripheral surface coming into contact with the inner peripheral surface in a sealing manner and is made of a rubber-like elastic material, a second gasket which is integrally bonded to the upper end surface coming into contact with the first end surface in a sealing manner and is made of a rubber-like elastic material, and a third gasket which is integrally bonded to the lower end surface coming into contact with the second end surface in a sealing manner and is made of a rubber-like elastic material. 
       Effect of the Invention 
       [0017]    The present invention achieves effects described below. 
         [0018]    According to the dust cover for the ball joint of the invention described in the first aspect, the dust cover for the ball joint is structured such that the rigid ring is pinched by the retainer having the C-shaped cross section. As a result, it is possible to securely suppress generation of the mouth-opening phenomenon of the small-diameter opening portion, and it is possible to more effectively inhibit the seal performance from being lowered in the small-diameter opening portion and inhibit the sedimentation or the garbage from entering into the dust cover from the external portion. 
         [0019]    Further, according to the dust cover for the ball joint of the invention described in the second aspect, the material of the gasket is set to a silicone rubber. As a result, it is possible to effectively suppress generation of the so-called mouth opening phenomenon of the small-diameter opening portion even under the low-temperature atmosphere. 
         [0020]    Further, according to the dust cover for the ball joint of the invention described in the third aspect, the rigid ring is pinched by the retainer having the L-shaped cross section and the knuckle. As a result, it is easy to assemble the retainer, it is possible to suppress generation of the so-called mouth opening phenomenon of the small-diameter opening portion even under the low-temperature atmosphere, and it is possible to effectively inhibit the seal performance from being lowered in the small-diameter opening portion, and inhibit the sedimentation or the garbage from entering into the dust cover from the external portion. 
         [0021]    Further, according to the dust cover for the ball joint of the invention described in the fourth aspect, the dust lip coming into contact with knuckle in the sealing manner and made of the rubber-like elastic material is integrally bonded to the second end surface side of the rigid ring. As a result, it is easy to assemble the retainer, and it is possible to more effectively inhibit the sedimentation or the garbage from entering into the dust cover from the external portion. 
     
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
         [0022]      FIG. 1  is a vertical cross sectional view of a dust cover for a ball joint according to the present invention; 
           [0023]      FIG. 2  is a vertical cross sectional view of a dust cover single body shown in  FIG. 1  before being installed; 
           [0024]      FIG. 3  is a vertical cross sectional view of a retainer single body shown in  FIG. 1  before being assembled; 
           [0025]      FIG. 4  is a vertical cross sectional view of a state in which the retainer in  FIG. 3  is assembled in the dust cover in  FIG. 2 ; 
           [0026]      FIG. 5  is a vertical cross sectional view of a retainer according to a second embodiment of the present invention; 
           [0027]      FIG. 6  is a vertical cross sectional view of a retainer according to a third embodiment of the present invention; 
           [0028]      FIG. 7  is a vertical cross sectional view of a retainer according to a fourth embodiment of the present invention; 
           [0029]      FIG. 8  is a vertical cross sectional view of a retainer according to a fifth embodiment of the present invention; 
           [0030]      FIG. 9  is a view showing a dust cover which is assembled with the retainer shown in  FIG. 8  in the same manner as  FIG. 2 ; 
           [0031]      FIG. 10  is a view showing a state in which the retainer shown in  FIG. 8  is assembled in the dust cover shown in  FIG. 9  in the same manner as  FIG. 1 ; and 
           [0032]      FIG. 11  is a vertical cross sectional view of a dust cover for a ball joint according to a prior art. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0033]    A description will be given below of an embodiment for carrying out the present invention. 
         [0034]    As shown in  FIGS. 1 to 4 , a dust cover for a ball joint according to the present invention is basically structured such that a spherical head portion  2  formed in one end of a ball stud  1  is retained within a socket  3 , a shaft  4  in the other end of the ball stud  1  is fastened and fixed to a knuckle  5 , a one end large-diameter opening portion  8  is fixed and retained to an outer peripheral surface of the socket  3 , the other end small-diameter portion  7  having a rigid ring  9  integrally formed therein is retained to the shaft  4 , and a film portion  61  is provided for connecting the one end large-diameter opening portion  8  and the other end small-diameter opening portion  7 . 
         [0035]    Further, as shown in  FIG. 2 , the rigid ring  9  approximately has a rectangular cross section, one end of a film portion  61  is connected to an outer peripheral surface side of the rigid ring  9 , and the rigid ring  9  is structured such as to be exposed at least in an inner peripheral surface  92 , a first end surface  92  in the socket  3  side, and a second end surface  93  in the knuckle  5  side. 
         [0036]    As a material of the rigid ring  9 , metal materials and various resin materials are appropriately selected and employed. 
         [0037]    Further, a retainer  10  shown in  FIG. 3  is assembled in the rigid ring  9  as shown in  FIG. 4 , and is thereafter fitted and fixed to an outer peripheral surface of the shaft  4  as shown in  FIG. 1 . 
         [0038]    The retainer  10  has a cylinder portion  11  which is provided with an outer peripheral surface  11  facing to an inner peripheral surface  91 , a first flange portion  12  which is provided with an upper end surface  121  facing to a first end surface  92 , and a second flange portion  13  which is provided with a lower end surface  131  facing to a second end surface  93 . The retainer  10  is provided with a first gasket  112  which is integrally bonded to an outer peripheral surface  111  coming into contact with the inner peripheral surface  91  in a sealing manner and is made of a rubber-like elastic material, a second gasket which is integrally bonded to an upper end surface  121  coming into contact with the first end surface  91  in a sealing manner and is made of a rubber-like elastic material, and a third gasket  132  which is integrally bonded to a lower end surface  131  coming into contact with the second end surface  93  in a sealing manner and is made of a rubber-like elastic material. In other words, the retainer  10  is provided with three kinds of gaskets  112 ,  122  and  132 . 
         [0039]    A method of assembling the retainer  10  shown in  FIG. 3  in the rigid ring  9  as shown in  FIG. 4  is structured such that the rigid ring  9  is enwrapped by the retainer as shown in  FIG. 4  by inserting the rigid ring  9  onto the retainer  10  in a state in which the first flange portion  12  extends downward in an axial direction as shown by a broken line in  FIG. 3 , and next folding the first flange portion  12  to an outer side in a diametrical direction as shown by a solid line in  FIG. 3 . 
         [0040]    The first flange portion  12  may be structured such as to be divided into a plurality of pieces for being easily folded. 
         [0041]    As a result, the first gasket  112 , the second gasket  122  and the third gasket  132 , totally three kinds of gaskets  112 ,  122  and  132  respectively come into elastic contact with the inner peripheral surface  91 , the first end surface  92  and the second end surface  93  of the rigid ring  9 . Therefore, it is possible to securely suppress generation of a mouth opening phenomenon of the small-diameter opening portion  7 , and it is possible to effectively inhibit a seal performance from being lowered in the small-diameter opening portion  7 , and inhibit the sedimentation or the garbage from entering into the dust cover from an external portion. 
         [0042]    As a material of the retainer  10 , metal materials and various resin materials are appropriately selected and employed. 
         [0043]    Further, a silicone rubber is used as the material of the first gasket  112 , the second gasket  122  and the third gasket  132 , totally three kinds of gaskets  112 ,  122  and  132 . 
         [0044]    As a result, it is possible to effectively suppress generation of the so-called mouth opening phenomenon of the small-diameter opening portion, even under a low-temperature atmosphere. 
         [0045]    However, the material of the first gasket  112 , the second gasket  122  and the third gasket  132 , totally three kinds of gaskets  112 ,  122  and  132  is not limited to the silicone rubber, but various rubber materials can be appropriately combined and used according to a used condition, and the materials of three kinds of gaskets  112 ,  122  and  132  may be different from each other. 
         [0046]    A usable rubber material can employ by appropriately selecting various rubber-like elastic materials such as FKM having a good sealing performance, a silicone rubber, EPDM, a nitrile rubber, an acrylic rubber and HNBR. 
         [0047]    Further, a collapsing ratio in a state in which the first gasket  112 , the second gasket  122  and the third gasket  132  are assembled is preferably set to a range between 10 and 35% for maintaining the seal performance. 
         [0048]    Further, a material of the elastic dust cover  6  can be appropriately selected and used according to an intended use from rubber-like elastic materials such as chloroprene, polyester elastomer and thermoplastic elastomer such as thermoplastic polyurethane. 
         [0049]    Further, a grease is sealed within the dust cover  6  made of the elastic material. 
         [0050]    The embodiment mentioned above is structured such that the retainer  10  is provided with the first gasket  112 , the second gasket  122  and the third gasket  132 , totally three kinds of gaskets  112 ,  122  and  132 , however, three kinds of gaskets  112 ,  122  and  132  are not necessarily provided. In any of a structure in which two kinds of gaskets including the first gasket  112  and the second gasket  122  are provided like a second embodiment shown in  FIG. 5 , two kinds of gaskets including the first gasket  112  and the third gasket  132  are provided like a third embodiment shown in  FIG. 6 , and two kinds of gaskets including the second gasket  122  and the third gasket  132  are provided like a fourth embodiment shown in  FIG. 7 , it is possible to effectively suppress generation of the so-called mouth opening phenomenon of the small-diameter opening portion, even under the low-temperature atmosphere. 
         [0051]    Next, a description will be given of a retainer  10  according to a fifth embodiment of the present invention with reference to  FIGS. 8 to 10 . 
         [0052]    A different point from the retainer  10  described above is a matter that the retainer is formed into an L-shaped form in its cross section and a portion corresponding to the second flange portion  13  does not exist. 
         [0053]    In other words, the retainer  10  according to the fifth embodiment has a cylinder portion  11  which is fitted and fixed to the outer peripheral surface of the shaft  4  and is provided with an outer peripheral surface  111  facing to the inner peripheral surface  92 , and a first flange portion  12  which is provided with an upper end surface  121  facing to the first end surface  92 , and is constructed by integrally bonding a first gasket  112  coming into contact with the inner peripheral surface  91  in a sealing manner and made of a rubber-like elastic material to the outer peripheral surface  111 , and integrally bonding a second gasket  122  coming into contact with the first end surface  92  in a sealing manner and made of a rubber-like elastic material to the upper end surface  121 . 
         [0054]    According to the structure mentioned above, the retainer  10  does not require any folding process as is different from the previous embodiments, and it is easy to assemble the retainer. 
         [0055]    Further, the rigid ring  9  is structured such that the rigid ring  9  is pinched by the retainer  10  and the knuckle  5 . 
         [0056]    As a result, the sealing performance can be further enhanced by integrally bonding a dust lip  931  coming into contact with the knuckle  5  in a sealing manner and made of a rubber-like elastic material to the second end surface  93  side of the rigid ring  9  as shown in  FIG. 9 , it is possible to suppress generation of the so-called mouth opening phenomenon of the small-diameter opening portion  7  even under the low-temperature atmosphere, and it is possible to effectively inhibit the seal performance from being lowered in the small-diameter opening portion  7 , and inhibit the sedimentation or the garbage from entering into the dust cover from the external portion. 
         [0057]    Here, the material of the dust lip  931  may be the same material as that of the film portion  61 , or may be the same material as that of the first gasket  112  and the second gasket  122 . 
         [0058]    On the other hand, the one end large-diameter opening portion  8  having the approximately C-shaped cross section in the dust cover  6  made of the elastic material is structured such as to be fixed and retained within an annular groove portion  31  which is formed in the outer peripheral surface of the socket  3 , by an annular pressure ring  70 . 
         [0059]    A circlip approximately having a rectangular cross section is used for the pressure ring  70 . 
         [0060]    Further, it goes without saying that the present invention is not limited to the best mode for carrying out the invention mentioned above, but can employ the other various structures without deviating from the scope of the present invention. 
       INDUSTRIAL APPLICABILITY 
       [0061]    The present invention can be used in the ball joint which is used in the suspension device and the steering device of the motor vehicle.