Abstract:
A ball joint having a cylindrical housing containing a plurality of projections. A cylindrical ball seat is inserted within the housing and secured to the housing by the plurality of projections. A ball stud having a spherical head portion is rotatably disposed within the ball seat, and a cap is disposed at and secured to the lower, outside portion of the ball seat.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a ball joint device for use in a joint of steering or suspension systems of automobiles, and more particularly to a ball joint of automobiles which removes the damage caused by twist occurring in the assembly process. 
     2. Description of Related Art 
     Various types of ball joints for use in a vehicle are well known in the art. A ball joint rotatably and tiltable on any plane surface is generally used for a steering or a suspension system of automobiles. A conventional ball joint has a structure in which a spherical head of a ball stud is inserted into the inside of a ball seat under the condition that its rotational and tilt operation is enabled; the ball seat is fixed to a housing and a dust cover is fixed between the cross portion of a housing and a ball seat. 
     FIGS. 1 and 4 show an existing ball joint disclosed in Japanese Laid-Open Patent No. Hei 1-172610. A ball seat  102  where a spherical head  101   a  of a ball stud  101  movably inserted is installed in a housing  103 . And then a combining plate  102   a  provided at the closed portion of the ball seat  102  is heated to be bent outwardly so that the combining plate  102   a  is hook-combined with the lower portion of the housing  103 . That is, one plate of a dust cover  104  is fixed by a rib  105  at a groove formed between a hook protrusion  102   b  of the ball seat  102  and a step of the housing  103 . 
     In such a ball joint, the combining plate  102   a  provided at the lower portion of the ball seat  102  is heated and melted to be bent to the outward of the lower portion of the housing  103 , thus being hook-combined. 
     To prevent the ball seat  102  inserted into the housing  103  from rotating while in operation, a V-shaped fixing groove (not shown) is provided at the step of the housing  103  where the combining plate  102   a  of the ball seat  102  is hook-combined with the housing  103 , and melted by heating. Thus, the rotation of the combining plate  102   a  of the ball seat  102  is prevented. 
     However, such a ball joint must be additionally provided with the V-shaped fixing groove, and the combining plate  102   a  must be heated during a manufacturing process adding difficulty and cost to the process. The combining strength between the ball seat  102  and the housing  103  is increased when the thickness of the combining plate  102   a  formed on the ball seat  102  is thickened. However, when the combining plate  102   a  is thickened, it is more difficult to melt. 
     As shown in FIGS. 2 and 4, a ball joint in which a housing  103  where a support formed of a metallic material is welded is provided. After the ball seat  102  formed of a plastic material (including the spherical head  101   a  of the ball stud  101 ) is inserted into the housing  103 , a covering cap  106  formed of a plastic material is welded to the lower portion of the ball seat  102  by an ultrasonic vibrator. While welding protrusions  106   a  formed on the covering cap  106  are melted and welded, the ball seat  102  is fixed to the housing  103 . Such a ball joint is disclosed in U.S. Pat. No. 5,011,321 to Kidokoro. 
     However, the method in which that the ball seat  102  is fixed to the housing  103  by welding a covering cap  106  to the ball seat  102  requires additional equipment, and further, requires an apparatus for verifying the welding state. Though the verification apparatus is employed, it is not easy to verify the state of weldment of the covering cap  106  onto the ball seat  102  with accuracy. 
     FIGS. 3 and 4, disclose and alternative ball joint. An outwardly bent annular hook protrusion  102   c  is made at the closing portion of a ball seat  102  where a spherical head  101   a  of a ball stud  101  is inserted. An annular hook protrusion  102   c  is hooked and fixed at the lower portion of a housing  103 , and thus the ball seat  102  is fixed to the housing  103 . The diameter of the annular hook protrusion  102   c  formed at the closing portion of the ball seat  102  is formed to be greater than that of the ball seat  102 . Such a ball joint is disclosed in Japanese Utility Laid-Open Patent No. Hei 5-23852. 
     However, in such a ball joint, the annular hook protrusion  102   c  may become damaged when a ball seat  102  is inserted in a housing  103 , and a combining strength of an annular hook protrusion  102   c  of the ball seat  102  being hooked and fixed to the housing  103  is weak. 
     That is, the ball seat  102  is generally inserted by using a tool. Accordingly, when the ball seat  102  does not uniformly receive force from the tool for inserting the ball seat  102  into a housing  103 , the ball seat  102  is twisted. Also, when a twisted ball seat  102  is assembled into the housing  103 , an annular hook protrusion  102   c  is easily broken since the diameter of the annular hook protrusion  102   c  is formed to be greater than that of the ball seat  102 . When the ball seat  102  slips out of the housing  103  by a vertical force of a ball stud  101  during operation of the ball joint, the annular hook protrusion  102   c  cannot withstand the force and is damaged. 
     FIGS. 5 and 6 illustrate another existing ball joint. The first hook protrusion  112   a  and the second hook protrusion  112   b  are formed at the open portion of a ball seat  112  and a dust cover  104  is fixed by a rib at a fixing groove  112   c  formed between the first hook protrusion  112   a  and the second hook protrusion  112   b.  This configuration avoids the likelihood that the dust cover  104  will receive much stress by the operation of a ball joint, such as by shaking and rotating, and makes assembly process automation possible by inserting a ball seat  112  into a housing  113  and fixing it, then fixing a dust cover  104 . Such a ball joint is disclosed in U.S. Pat. No. 5,676,485 to Lee. 
     In order to solve problems such as when a ball seat  112  turns inside a housing during the operation of a ball joint and the ball seat  112  gets twisted and damaged by a tool when the ball seat  112  is inserted into the housing  113 , the inside of the housing  113  and the outer body of the ball seat  112  have the same polygonal shape and several incised plates are formed at an annular hook sill  112   d  formed on the ball seat  112 . 
     In addition, to fix a ball seat  112  in a housing  113  and maintain the fixing strength, a cap  114  is placed on an annular hook sill  112   d  formed at the lower closing portion of the ball seat  1122 . However, the ball joint above has the problem that it can&#39;t be easily assembled by an automated process because a ball seat  112  must be inserted into a housing  113  with their polygonal angle being conformed. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide an improved ball joint device for use in a vehicle which eliminates the aforementioned problems encountered with conventional ball joint devices. 
     Another object of the present invention is to provide a ball joint for use in a vehicle which does not experience the damage caused by twist occurring in the assembly process. To realize the above-mentioned objects, a ball joint of an automobile comprises a spherical head of a ball stud inserted inside of a ball seat under the condition that rotational and tilt operation is enabled. The ball seat above is fixed to a housing and a dust cover is fixed to a fixing groove formed on the outer portion of a ball seat by a rib. A ball joint of automobiles installed on an annular hook sill formed at a cap extending from the other side of the ball seat in the length direction, comprises several projecting parts projected in the radial direction and formed in the direction of length inside of the housing. The housing contains a round section and a concave sill formed at the outside of an annular hook sill. 
     Still another object of the present invention is to provide a ball joint device for use in a vehicle, which is simple in structure, inexpensive to manufacture, durable in use, and refined in appearance. 
     Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a sectional view of a conventional ball joint device as one example; 
     FIG. 2 is a sectional view of a conventional ball joint device as another example; 
     FIG. 3 is a sectional view of a conventional ball joint device as a further example; 
     FIG. 4 is a cross-sectional view of FIG. 5; 
     FIG. 5 is a sectional view of a conventional ball joint device as still another example; 
     FIG. 6 is a cross-sectional view of FIG. 5; 
     FIG. 7 is a sectional view of a ball joint device for use in a vehicle according to the present invention; 
     FIG. 8 is a cross-sectional view of FIG. 7, taken along line A—A; 
     FIG. 9 is an exploded sectional view of a ball seat and a housing of the ball seat device for use in a vehicle according to the present invention; and 
     FIG. 10 is an enlarged sectional view of part B of FIG.  10 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, the ball joint device for use in a vehicle as shown in FIGS. 7 to  10  includes a spherical head  1   a  of a ball stud  1  inserted inside of a ball seat  2  under the condition that rotational and tilt operation is enabled, the ball seat  2  above is fixed to a housing  3  and a dust cover  4  is fixed to a fixing groove  2   a  formed on the outer portion of a ball seat  2  by a rib  5 . A cap  6  is installed on an annular hook sill  2   b  which extends from one plate of a ball seat  2 . 
     The ball stud  1  above is composed of a spherical head  1   a,  and a screw portion  1   b,  the other portion of the ball stud, is connected to some portion with control of rotation and angle enabled. 
     The ball seat  2  has the shape of a cylinder open to one side, having an open portion where a spherical head  1   a  of the ball stud  1  is installed. In drawing, a fixing groove  2   a  is formed at the outer portion of the upper side in the radial direction. At the lower portion, several projecting annular hook sills  2   b  extended and divided in the direction of height are formed. A concave sill  2   d  is formed at the lower portion outside the annular hook sill  2   b.    
     The section of the annular hook sill  2   b  has a downwardly pointed shape. It is desirable to make the outside diameter of the lowermost portion less than the inside diameter of said housing  3  by 1 mm. Also, a groove  2   c  for cap installation is formed inside the annular hook sill  2   b  of the ball seat  2  in the radial direction. Corresponding to this, protrusion  6   a  is formed around said cap  6 . Accordingly, said cap  6  is easily fixed when it is inserted into the annular hook sill  2   b.    
     The housing above  3 , having the shape of a cylinder having a round section, has several projecting parts  3   a  projected in the radial direction and formed in a lengthwise direction. The ball joint formed as this, by making the outside of a ball seat and the inside of a housing a circle, can be inserted without considering direction, which allows for an automated assembly process. When the ball seat  2  is inserted into a housing  3  by force, the projecting part  3   a  of the housing  3  drives into the outside of the ball seat  2  by force, then gets inserted and assembled. When assembling, putting the ball seat  2  on the upper portion of the housing  3  allows for process automation. 
     That is, since the outside diameter of an annular hook sill is less than the inside diameter of a housing by 1 mm and a concave sill is formed around the outside of the annular hook sill, the ball seat can be placed on the upper portion of the housing. 
     A ball stud assembled through this process secures the ball sent to the ball stud even though the ball stud rotates and tilts. 
     Accordingly, as described above, referring to the ball joint device of an automobile of the present invention, since the outside of the ball seat and the inside of the housing have a round section as well as a protrusion formed inside the housing, it can be inserted without positional adjustment, and the ball seat is easily fixed to the housing, consequently, in case the ball stud moves, the ball seat becomes unmovable. As a result, the advantage follows to lessening the damage of said ball seat. By forming a concave sill between the outside of an annular hook sill as well as making the diameter of the closing portion of the annular hook sill less than the inside diameter of the housing by 1 mm, whenever the ball seat is placed on the housing, said ball seat assumes its proper position on the housing, and which removes twist during insertion, which results in ease of process automation. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art were intended to be included within the scope of the following claims.