Patent Publication Number: US-2020277984-A1

Title: Dust cover for ball joint and method of attaching the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage Application of International Application No. PCT/JP2016/082714, filed on Nov. 2, 2016, and published in Japanese as WO 2017/086178 on May 26, 2017 and claims priority to Japanese Application No. 2015-228170, filed on Nov. 20, 2015. The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The present invention relates to a dust cover for a ball joint and a method of attaching the dust cover for a ball joint. More specifically, the present invention relates to a dust cover for a ball joint to be mounted on a ball joint in which a knuckle of pinch bolt type having a knuckle groove is fastened and fixed to a shaft of a ball stud, and to a method of attaching the dust cover for the ball joint. 
     Related Art 
     Many ball joints are used in suspension systems and steering systems of automobiles, for example. A ball joint is filled with grease to smooth the motion, and is covered with a dust cover to prevent a leak of the grease and an entry of foreign matter such as water and dust from the outside. 
     Ball joints are divided broadly into taper alignment ball joints and pinch bolt ball joints depending on how to fasten a knuckle to a ball stud. 
     For a taper alignment ball joint, the position of a knuckle  200  is determined so that a tapered outer peripheral surface  100   a  of a shaft  100  of the ball stud overlaps an inner peripheral surface  200   a  of the knuckle  200 , as illustrated in  FIG. 8 . In this case, a dust cover seals the shaft  100  and a lower end face  200   b  of the knuckle  200  by providing seal lip parts so as to come into close contact with both the shaft  100  and the lower end face  200   b.  Thus, sealed areas by the dust cover are formed extending from the shaft  100  of the ball stud to the lower end face  200   b  of the knuckle  200 , as indicated by signs S 1  and S 2  in  FIG. 8 . 
     By contrast, a pinch bolt ball joint has a structure in which the knuckle  200  of pinch bolt type is fastened and fixed to the shaft  100  of the ball stud with a bolt  300 , as illustrated in  FIG. 9( a )  and  FIG. 9( b ) . In this case, a knuckle groove (slitting groove)  201  is formed in the knuckle  200 , which fails to provide any sealed area of the dust cover to the lower end face  200   b  of the knuckle  200  in the same manner as the taper alignment ball joint. For this reason, there is only one sealed area formed on the outer peripheral surface  100   a  of the shaft  100 , as indicated by a sign S in the figure, so that the pinch bolt ball joint has such a structure that water or foreign matter enters easily from the knuckle groove  201 . 
     Conventionally, a dust cover  400  has been proposed that includes a dust cover body  401  and an annular plate member  402  as a measure against the above, as illustrated in  FIG. 10  (JP- 2015 - 152058 -A).  FIG. 10( a )  is an enlarged sectional view illustrating sealed areas of the dust cover  400 .  FIG. 10( b )  is a plan view of the plate member  402 . 
     The plate member  402  includes an annular board member  402   a  made of a hard material and an annular sealing part  402   b  that is integrally formed on the inner peripheral side of the annular board member  402   a  and is made of a rubber elastic material. The plate member  402  is interposed between the dust cover body  401  and the knuckle  200 . The annular sealing part  402   b  is disposed so as to protrude to the surface on the knuckle  200  side of the annular board member  402   a.  An annular step  202  to accommodate the annular sealing part  402   b  is formed in the lower end part on the inner peripheral side of the knuckle  200 . The plate member  402  is provided with an engaging projection  402   c  that is made of a rubber elastic material and that engages with the knuckle groove  201 , on the surface on the knuckle  200  side of the annular board member  402   a  that is located on the outer peripheral side of the annular sealing part  402   b.  This structure prevents the plate member  402  from rotating with respect to the knuckle  200 . 
     With the dust cover  400 , the annular board member  402   a  of the plate member  402  can block the lower end face side of the knuckle groove  201 , which enables a sealed area to be formed on the knuckle  200  side by bringing a seal lip part  401   a  disposed in the upper end part of the dust cover body  401  into close contact with the lower face of the annular board member  402   a.  Consequently, the sealed area can be formed extending from the shaft  100  of the ball stud to the knuckle  200  side as in the case of the taper alignment ball joint. 
     As described above, the dust cover  400  disclosed in JP-2015-152058-A enables a seal area to be formed as in the case of the taper alignment ball joint, so that the dust cover  400  produces a beneficial effect of surely preventing an entry of foreign matter. The following new problems, however, have been found as a result of an earnest examination made by the present inventor aiming to further improve the technology. 
     The conventional dust cover  400  has the plate member  402  between the dust cover body  401  and the knuckle  200 , as illustrated in  FIG. 10( a ) , so that a seal width W 2  with respect to the shaft  100  of the ball stud corresponds to a normal seal width W 21  of the dust cover body  401  alone with a seal width W 22  of the annular sealing part  402   b  of the plate member  402  added thereto. In other words, the seal width is increased by the width of the plate member  402  disposed. In this case, because the length of the shaft  100  protruding from the lower end of the knuckle  200  cannot be changed in terms of design, there is a problem in that the annular step  202  to accommodate the annular sealing part  402   b  needs to be newly formed in the knuckle  200  in order to absorb the increased width of the seal width W 22 . 
     Mounting work of the dust cover  400  is performed by mounting the dust cover body  401  and the plate member  402  to the shaft  100 , and then attaching the knuckle  200  to the shaft  100  and fastening the knuckle  200  with the bolt  300 . When the knuckle  200  is attached, the plate member  402  is rotated around the shaft and the engaging projection  402   c  is positioned to be aligned with the position of the knuckle groove  201 , and then the knuckle groove  201  pinches and holds the engaging projection  402   c.  This problematically requires the work of matching the phases of the knuckle groove  201  and the engaging projection  402   c  when the dust cover  400  is mounted. Typically, ball joints are arranged in a narrow space in many cases, and it is thus desirable to save the work of matching the phase of the plate member  402  with that of the knuckle groove  201  in positioning the plate member  402  in order to further improve workability. 
     It is an object of the present invention to provide a dust cover for a ball joint, the dust cover including a dust cover body and a plate member, that can minimize the seal width with respect to a shaft of a ball stud and eliminate the need to machine a knuckle, and that can also save the work of matching the phase of the plate member with that of a knuckle groove in positioning the plate member when the dust cover is mounted. 
     It is another object of the present invention to provide a method of attaching the dust cover for a ball joint by which the work can be saved of matching the phases of the plate member and the knuckle groove when the dust cover is mounted, to easily position the plate member. 
     Other objects of the present invention will be apparent from the following description. 
     SUMMARY OF THE INVENTION 
     The above-described problems are solved by the following respective inventions. 
     In a first aspect, a dust cover is provided for a ball joint to be mounted on a ball joint in which a knuckle of pinch bolt type having a knuckle groove is fastened and fixed to a shaft of a ball stud. The dust cover for a ball joint comprises:
         a dust cover body made of a rubber elastic material; and   an annular plate member that is interposed between the dust cover body and the knuckle, wherein   in the dust cover body, a reinforcement ring is disposed in a stud mounting part that is mounted on an outer peripheral surface of the shaft, and on an inner peripheral side of the reinforcement ring, an annular step is formed having a shape of being cut out at a certain depth from the knuckle side,   the plate member includes a plate body and an annular sealing part, the annular sealing part being made of a rubber elastic material, disposed on an inner peripheral side of the plate body, and accommodated in the annular step of the dust cover body, and   in an outer periphery of the plate body, a plurality of cut parts are formed, so that outer peripheral petal parts are formed between adjacent cut parts to be capable of being bent so as to be engaged with a knuckle groove.       

     In a second aspect, in the dust cover for a ball joint according to the first aspect, an upper end outer peripheral part of the stud mounting part in the dust cover body has a first seal lip part for sealing a space with a lower face of the plate body in the plate member, and an outer peripheral surface of the annular sealing part in the plate member has a second seal lip part for sealing a space with an inner peripheral surface of the annular step. 
     In a third aspect, in the dust cover for a ball joint according to the second aspect,
         the reinforcement ring is exposed to the annular step, and   the second seal lip part seals a space with an inner peripheral surface of   the reinforcement ring that is exposed to the annular step.       

     In a fourth aspect, in the dust cover for a ball joint according to the first, second or third aspect, an inner peripheral surface of the stud mounting part in the dust cover body has a third seal lip part for sealing a space with the outer peripheral surface of the shaft. 
     In a fifth aspect, in the dust cover for a ball joint according to any one of the first to fourth aspects, an inner peripheral surface of the annular sealing part in the plate member has a fourth seal lip part for sealing a space with the outer peripheral surface of the shaft. 
     In a sixth aspect, a method of attaching the dust cover for a ball joint as in any one of the first to fifth aspects is provided. The method comprises:
         after mounting the dust cover body and the plate member to the shaft, attaching the knuckle to the shaft so as to sandwich the plate member with the dust cover body; and   positioning the plate body with respect to the knuckle by bending, of a plurality of outer peripheral petal parts formed in the plate body of the plate member, an outer peripheral petal part located in a position corresponding to the knuckle groove so as to be engaged with the knuckle groove.       

     Effect of the Invention 
     With the present invention, a dust cover for a ball joint, the dust cover including a dust cover body and a plate member, can be provided that can minimize the seal width with respect to a shaft of a ball stud and eliminate the need to machine a knuckle, and that can also save the work of matching the phase of the plate member with that of a knuckle groove in positioning the plate member when the dust cover is mounted. 
     With the present invention, a method of attaching the dust cover for a ball joint can also be provided, by which the work can be saved of matching the phases of the plate member and the knuckle groove when the dust cover is mounted, to easily position the plate member. 
    
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating an example of a pinch bolt ball joint to which a dust cover for a ball joint according to the present invention is mounted; 
         FIG. 2  is an exploded sectional view illustrating the dust cover for a ball joint according to the present invention; 
         FIG. 3  is a plan view of a plate member in the dust cover for a ball joint according to the present invention; 
         FIG. 4  is a sectional view of main parts of the pinch bolt ball joint to which the dust cover for a ball joint according to the present invention is mounted; 
         FIG. 5  is an explanatory view illustrating the way the dust cover for a ball joint according to the present invention is mounted on a shaft of a ball stud; 
         FIG. 6( a )  is an explanatory view illustrating the way a knuckle is attached to the shaft of the ball stud to which the dust cover for a ball joint according to the present invention is mounted;  FIG. 6( b )  is a plan view illustrating the way the knuckle is attached to the shaft of the ball stud to which the dust cover for a ball joint according to the present invention is mounted; 
         FIG. 7  is an explanatory view illustrating the way outer peripheral petal parts of the plate member are bent in a knuckle groove; 
         FIG. 8  is a side view of main parts of a taper alignment ball joint; 
         FIG. 9( a )  is a side view of main parts of a pinch bolt ball joint;  FIG. 9( b )  is a plan view of the main parts of the pinch bolt ball joint; 
         FIG. 10( a )  is a sectional view of main parts of a pinch bolt ball joint to which a conventional dust cover for a ball joint is mounted; and  FIG. 10( b )  is a plan view of a plate member in the conventional dust cover for a ball joint. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The following describes embodiments of the present invention with reference to the drawings. 
       FIG. 1  is a sectional view illustrating an example of a pinch bolt ball joint to which a dust cover for a ball joint according to the present invention is mounted.  FIG. 2  is an exploded sectional view illustrating the dust cover for a ball joint according to the present invention.  FIG. 3  is a plan view of a plate member in the dust cover for a ball joint according to the present invention.  FIG. 4  is a sectional view of main parts of the pinch bolt ball joint to which the dust cover for a ball joint according to the present invention is mounted. 
     As illustrated in  FIG. 1 , in a pinch bolt ball joint  10  (hereinafter referred to as the ball joint  10 ), a spherical head part  13  formed at one end of a shaft  12  of a ball stud  11  is rotatably held in a socket  14 . To the shaft  12 , a knuckle  15  of pinch bolt type having a knuckle groove  151  is fastened and fixed with a bolt  16 . A dust cover for a ball joint  1  according to the present invention (hereinafter referred to as the dust cover  1 ) is mounted so as to cover the space between a lower end face  15   a  of the knuckle  15  and the socket  14 . 
     The dust cover  1  includes a dust cover body  2  and a plate member  3  that is interposed between the dust cover body  2  and the knuckle  15 , as illustrated in  FIG. 2 . 
     The dust cover body  2  is formed of a rubber elastic material in a cup shape. One end (upper end in the figure) of the dust cover body  2  is a stud mounting part  21  into which the shaft  12  of the ball stud  11  is inserted, and the other end (lower end in the figure) thereof is a socket mounting part  22  that is mounted on the upper end part of the socket  14 . 
     The stud mounting part  21  is open having a smaller diameter than that of the socket mounting part  22  so that the shaft  12  of the ball stud  11  is inserted into the stud mounting part  21  and the stud mounting part  21  is slidably mounted on an outer peripheral surface  12   a  of the shaft  12 . A reinforcement ring  23  made of metal or hard synthetic resin is disposed in the stud mounting part  21 . The socket mounting part  22  is open having a larger diameter than that of the stud mounting part  21  so as to be fixed to the socket  14 . A reinforcement ring  24  made of metal or hard synthetic resin is buried in the socket mounting part  22 . 
     In the upper end outer peripheral part of the stud mounting part  21 , an annular seal lip part  211  (first seal lip part) is formed to protrude obliquely outward that comes into close contact with the plate member  3  for sealing. On the inner peripheral surface of the stud mounting part  21 , seal lip parts  212  (third seal lip parts) are formed that come into close contact with the outer peripheral surface  12   a  of the stud  12  for sealing. 
     Furthermore, on the inner peripheral side of the reinforcement ring  23 , an annular step  25  is formed having a shape of being cut out annularly at a certain depth from above (the knuckle  15  side). Thus, the stud mounting part  21  is open in a shape having a portion of relatively large diameter in which the annular step  25  is formed and a portion of relatively small diameter that is integrally connected to the lower part of the annular step  25 . The portion of small diameter is a part that comes into contact with the outer peripheral surface  12   a  of the shaft  12  and in which the seal lip parts  212  is formed. The seal lip parts  212  are formed to have a slightly smaller inside diameter than the diameter of the shaft  12  so as to come into close contact with the outer peripheral surface  12   a  of the shaft  12 . 
     In the present embodiment, the reinforcement ring  23  shows a preferred mode in which a cylindrical part  231  running along the shaft  12  of the ball stud  11  and a flange  232  overhanging toward the outside in the upper end part of the cylindrical part  231  are included to be formed in an inverted-L shape in section. In the reinforcement ring  23 , substantially half of the cylindrical part  231  on the lower end side is arranged in the rubber elastic material that constitutes the stud mounting part  21 . The inner peripheral surface on the upper end side of the cylindrical part  231  is exposed in the annular step  25 . In other words, an inner peripheral surface  25   a  of the annular step  25  is defined by the inner peripheral surface of the cylindrical part  231  in the reinforcement ring  23 . 
     Meanwhile, the plate member  3  includes a plate body  31  and an annular sealing part  32 . 
     The plate body  31  is made of an annular board member having a larger diameter than the outside diameter of the stud mounting part  21  in the dust cover body  2 , specifically, than the outside diameter of the seal lip part  211 . The plate body  31  is formed to have a slightly larger inside diameter than the diameter of the shaft  12 . 
     In the outer periphery of the plate body  31 , a plurality of cut parts  311  are formed at a fixed interval, as illustrated in  FIG. 3 . Thus, the plate body  31  has the shape of a toothed wheel, and portions between adjacent cut parts  311 ,  311  are outer peripheral petal parts  312 . A width L 1  of each outer peripheral petal part  312  in the circumferential direction is set to be the same as or slightly smaller than a width L 2  (see  FIG. 6( b ) ) of the knuckle groove  151  so as to be capable of being engaged with the knuckle groove  151  with the knuckle  15  fastened and fixed to the shaft  12  with the bolt  16 . 
     The outer peripheral petal parts  312  of the plate body  31  are structured to be capable of being easily bent by hand by using an appropriate jig such as a screwdriver so as to be engaged with the knuckle groove  151 . Preferably, the plate body  31  itself can be bent and is made of a material that can maintain the bent state once it is bent. Specific examples of the material include a cold-reduced carbon steel sheet (SPCC material) and a stainless steel material (SUS material). 
     Although the illustrated cut parts  311  are formed by the respective U-shaped cut out grooves in plan view, the cut parts  311  may be narrower slits and the specific shape thereof does not matter. However, a width L 3  of each cut part  311  in the circumferential direction is preferably smaller than the width L 1  of the outer peripheral petal part  312 . Because a large number of outer peripheral petal parts  312  can be formed in the plate body  31 , any of the outer peripheral petal parts  312  is arranged all the more easily in the position corresponding to the knuckle groove  151 , which allows workability to be more favorable in bending the outer peripheral petal parts  312  to be engaged with the knuckle groove  151 . 
     The annular sealing part  32  is made of the same rubber elastic material as the dust cover body  2 , and is disposed in the inner peripheral part of the plate body  31  so as to protrude toward the dust cover body  2  side. The annular sealing part  32  is accommodated in the annular step  25  of the dust cover body  2  with the dust cover  1  mounted on the ball joint  10 , as illustrated in  FIG. 1  and  FIG. 4 . 
     The annular sealing part  32  does not protrude to the knuckle  15  side, and the surface on the knuckle  15  side of the plate member  3  is formed to be flush with the lower end face  15   a  of the knuckle  15  extending from the plate body  31  to the annular sealing part  32  so that the flat surface of the plate member  3  can be brought into close contact with the flat surface of the lower end face  15   a.    
     A seal lip part  321  (second seal lip part) is formed on the outer peripheral surface of the annular sealing part  32 . The seal lip part  321  is formed to have a slightly larger outside diameter than the inside diameter of the annular step  25  in the dust cover body  2 . Consequently, the seal lip part  321  comes into close contact with the inner peripheral surface  25   a  of the annular step  25  for sealing. 
     Seal lip parts  322  (fourth seal lip parts) are formed on the inner peripheral surface of the annular sealing part  32 . The seal lip parts  322  are formed to have an inside diameter equal to the inside diameter of the seal lip parts  212  in the stud mounting part  21  of the dust cover body  2 . Consequently, the seal lip parts  322  come into close contact with the outer peripheral surface  12   a  of the shaft  12  for sealing. 
     When the dust cover  1  structured as described above is mounted on the ball joint  10 , the annular sealing part  32  of the plate member  3  is accommodated in the annular step  25  of the dust cover body  2  so as not to protrude toward the knuckle  15  side. This structure requires no need of adding an annular step for accommodating the annular sealing part to the knuckle as in the conventional example illustrated in  FIG. 10( a ) . 
     Because the dust cover  1  has a structure in which the annular sealing part  32  of the plate member  3  is accommodated in the annular step  25  of the dust cover body  2 , as illustrated in  FIG. 4 , a seal width W 1  with respect to the outer peripheral surface  12   a  of the shaft  12  is substantially no more than the axial width of the stud mounting part  21 , enabling the seal width W 1  to be minimized. Consequently, while the dust cover  1  includes the dust cover body  2  and the plate member  3 , the seal width W 1  with respect to the shaft  12  is no more than the seal width W 21  of the conventional dust cover body  401  illustrated in  FIG. 10( a ) , which can reduce the seal width W 1  to be no more than the seal width in the conventional dust cover in which no plate member is disposed. For this reason, the position of the stud mounting part  21  with respect to the shaft  12  is not shifted to the socket  14  side compared with the conventional dust cover, nor is the internal volume of the dust cover  1  reduced. 
     Furthermore, because a plurality of outer peripheral petal parts  312  of the plate member  3  can be bent, any of the outer peripheral petal parts  312  located in the position corresponding to the knuckle groove  151  can be bent to the knuckle groove  151  side to be engaged with the knuckle groove  151 . This work can be performed after the knuckle  5  is fastened and fixed to the shaft  12 . Additionally, the plate member  3  does not need to be rotated to a large extent in order to match the phases of the knuckle groove  151  and the outer peripheral petal part  312 . This can eliminate the work of matching the phase of the plate member  3  with that of the knuckle groove  151  by rotating the plate member  3  as in the conventional example when the plate member  3  is positioned, thereby substantially improving workability in mounting the dust cover. 
     As illustrated in  FIG. 4 , with the annular sealing part  32  accommodated in the annular step  25 , the seal lip part  211  of the dust cover body  2  comes into close contact with a lower face  31   a  of the plate body  31  in the plate member  3  to form a sealed area, and the seal lip part  321  of the plate member  3  comes into close contact with the inner peripheral surface  25   a  of the annular step  25  in the dust cover body  2  to form a sealed area. In other words, entry paths of water or foreign matter from the outside to the inside of the dust cover  1  are blocked in two places of the seal lip part  211  and the seal lip part  321 . Consequently, if water or foreign matter should pass through the outer seal lip part  211 , the inner seal lip part  321  can prevent water or foreign matter from entering the inside of the dust cover  1 . The double sealed areas can enhance the effect of preventing an entry of foreign matter. Moreover, sealed areas to the shaft  12  are also made up of the double sealed areas of the seal lip parts  212  and  322 , thereby enhancing the effect of preventing an entry of foreign matter along the shaft  12 . 
     In the present embodiment, the inner peripheral surface  25   a  of the annular step  25  with which the seal lip part  321  of the annular sealing part  32  comes into close contact is not made of a rubber elastic material but of the hard reinforcement ring  23 , thereby achieving stable sealing by the seal lip part  321 . 
     The following describes a method of attaching the dust cover  1  to the ball joint  10  with reference to  FIG. 5  to  FIG. 7 . 
     First, the dust cover body  2  and the plate member  3  are mounted on the shaft  12  of the ball stud  11 , as illustrated in  FIG. 5 . The annular sealing part  32  of the plate member  3  is accommodated in the annular step  25  of the dust cover body  2  at this time. 
     Next, the knuckle  15  is attached to the upper end part of the shaft  12  so as to sandwich the plate member  3  with the dust cover body  2 , and is fastened and fixed with the bolt  16 , as illustrated in  FIG. 6 . Of a plurality of outer peripheral petal parts  312  in the plate member  3 , a outer peripheral petal part  312  located in the position corresponding to the knuckle groove  151  is then bent to the knuckle  15  side by using an appropriate jig such as a screwdriver, to be engaged with the knuckle groove  151 , as illustrated in  FIG. 7 . In this way, the plate member  3  is positioned unrotatably to the knuckle  15 . 
     By this method of attaching the dust cover  1 , the plate member  3  can be positioned after the knuckle  15  is fastened and fixed to the shaft  12 . Because the phase of the plate member  3  does not need to be matched for positioning by rotating the plate member  3 , the plate member  3  can be positioned easily.